Living Environment/Biology Regents Cumulative Vocabulary Review Flashcards

Terms Definitions
Pathogens
Microbes that cause disease
First line of defense
includes skin, mucous membranes. not specialized for a particular invader. general defense against all kinds of pathogens.
second line of defense
Happens if first line is penetrated. Includes inflammatory response, temperature response, and proteins
inflammatory response
a protective response of tissues affected by disease or injury, characterized by redness, swelling, and pain
histamine
a regulating body substance released in excess during allergic reactions causing swelling and inflammation of tissues
phagocytes
allow lysosomes to fuse with the vesicles that contain the ingested bacteria and viruses
interferons
antiviral proteins secreted by T cells; they also stimulate macrophages to ingest bacteria
antigens
foreign substances that trigger the attack of antibodies in the immune response.
third line of defense
This includes Specialized Lymphocytes (T and B cells), and Antibodies
b lymphocytes
form in the bone marrow and release antibodies that fight bacterial infections.
t lymphocytes
destroy invading cells by producing killer substance near them (killer T cells). Some T cells attract other cells and these destroy the invader
antibodies
Specialized proteins that aid in destroying infectious agents.
plasma cells
cells that develop from B cells and produce antibodies.
memory cells
General term for lymphocytes that are responsible for the phenomenon of immunological memory and protective immunity. **
passive immunity
short-term immunity caused when antibodies produced by other animals for a pathogen are injected into the body
active immunity
a form of acquired immunity in which the body produces its own antibodies against disease-causing antigens
universal donor
A person with blood type O-. Because this person's red blood cells possess none of the typical blood suface proteins, they cannot initiate an immune reaction in a recipient.
universal recipient
A person with type AB blood has no antibodies against the other blood types and therefore, in an emergency, can receive any type of blood.
innate
existing from birth, inborn
Karl von frisch
discovered the honeybee's way of communicating about food -- waggle dance
Konrad Lorenz
researcher who focused on critical attachment periods in baby birds, a concept he called imprinting
Niko Tinbergen
known for his elucidation of the fixed action pattern, sticklebacks
Fixed Action Pattern
A sequence of behavioral acts that is essentially unchangeable and usually carried to completion once initiated.
Imprinting
evidence of critical period in some animals; they follow the first moving thing they see after hatching
Sign stimuli
An external sensory stimulus that triggers a fixed action pattern
releasers
sign stiumuli that are exchanged between members of the same species
learning
a relatively permanent change in an organism's behavior due to experience
habituation
decreasing responsiveness with repeated stimulation. As infants gain familiarity with repeated exposure to a visual stimulus, their interest wanes and they look away sooner
associative learning
learning that certain events occur together. The events may be two stimuli (as in classical conditioning) or a response and its consequences (as in operant conditioning)
classical conditioning
conditioning that pairs a neutral stimulus with a stimulus that evokes a reflex
b.f. skinner
pioneer of operant conditioning who believed that everything we do is determined by our past history of rewards and punishments. he is famous for use of his operant conditioning aparatus which he used to study schedules of reinforcement on pidgeons and rats.
operant conditioning
a type of learning in which behavior is strengthened if followed by a reinforcer or diminished if followed by a punisher
cooperation
behavior by two or more individuals that leads to mutual benefit
agnostic behavior
A type of behavior involving a contest of some kind that determines which competitor gains access to some resource, such as food or mates.
pecking order
a social system within a group of people or animals in which each member knows who has a higher or lower rank than themselves
territoriality
the behavior of a male animal that defines and defends its territory
altruism
unselfish concern for the welfare of others; selflessness
kin selection
The idea that evolution has selected altruism toward one's close relatives to enhance the survival of mutually shared genes
microevolution
evolution resulting from small specific genetic changes that can lead to a new subspecies
macroevolution
evolution on a large scale extending over geologic era and resulting in the formation of new taxonomic groups
transitional fossil
fossil that provides evolutionary change for the ancestors of modern animals
homologous structure
similar structure found in more than one species that share a common ancestor
analogous structure
structures that do not have a common evolutionary origin but are similar in function
vestigial structure
body structure that has no function in present day
theory of use and disuse
a. If you use a particular trait, it will be kept and passed on to next generation. b. If you don't use a particular trait, it will disappear
natural selection
a natural process resulting in the evolution of organisms best adapted to the environment
industrial melanism
darkening of populations of organisms over time in response to industrial pollution
stabilizing selection
form of natural selection by which the center of the curve remains in its current position; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end
diversifying selection
a type of evolution that simultaneously favors at both extremes of the distribution
directional selection
form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve
causes of variation in a population
mutations, genetic drift, migration
examples of genetic drift
bottleneck effect (decrease in a population size), and founder effect (small founding colony)
hardy-weinberg equilibrium
CRITERIA:
1. no gene flow
2. no mutations/crossover
3. random mating
4. no natural selection/limiting factors
5. infinite population size
forms of isolation
geographic, temporal, reproductive, habitat, behavioral
divergent evolution
when two or more species sharing a common ancestor become more different over time
convergent evolution
the process by which unrelated species become more similar as they adapt to the same kind of environment
parallel evolution
Two related species that have made similar evolutionary adaptations after their divergence from a common ancestor
co-evolution
process by which two species evolve in response to changes in each other
adaptive radiation
the development of many different forms from an originally homogeneous group of organisms as they fill different ecological niches
gradualism
The theory that evolution occurs slowly but steadily
punctuated equilibrium
a theory of evolution holding that evolutionary change in the fossil record came in fits and starts rather than in a steady process of slow change
Taxonomy
practice of classifying plants and animals according to their presumed natural relationships
Extremophiles
A prokaryote that lives in an extreme environment. Extremophiles include methanogens, extreme halophiles, and extreme thermophiles.
Carolus Linnaeus
Swedish botanist who proposed the modern system of biological nomenclature (1707-1778)
Binomial nomenclature
Classification system in which each species is assigned a two-part scientific name
Genus
(biology) taxonomic group containing one or more species
Species
(biology) taxonomic group whose members can interbreed
KPCOFGS
Kingdom, Phylum, Class, Order, Family, Genus, Species
Domain bacteria
a domain of prokaryotic bacteria the consists of cocci, bacilli, and spirilli shaped cells organized into strepto- and staphlo- groups, The domain of single celled, prokaryots with cell walls and circular chromosomes
Domain Archaea
Any of various single-celled prokaryotes genetically distinct from bacteria, often thriving in extreme environmental conditions
Kingdoms of Domain Eukarya
Protista, Animalia, Plantae and Fungi
Kingdom Protista
Eukaryotic; one celled and many celled; some move; some make own food others obtain it from other organisms
Kingdom fungi
kingdom composed of heterotrophs; many obtain energy and nutrients from dead organic matter
Kingdom plantae
eukaryotic, multicellular, autotrophic, cellulose-containing cell walls; chloroplasts containing chlorophyll a and b; asexual and sexual reproduction
Kingdom animalia
made up of eukaryotic, multicellular heterotrophic organisms
phylum of kingdom animalia
porifera, cnidarian, platyhelminthes, nematodes, annelids, mollusks, arthropoda, echinodermata, chordates
Phylum porifera
sponges; sessile (attached at base; don't move); 2 layers; filter feeders; body with pores
Phylum cnidarian
Hydras, corals, and jellies
a sac with a gastrovascular cavity
contains nematocytes for stinging food and enemy
Class: hydrozoa, cubazoa, anthozoa
Phylum platyhelminthes
flatworms; bilaterally symmetrical; 3 cell layers; gut with one opening; many parasitic **
Phylum nematodes
round worms--one way digestive system, mouth to anus
Phylum annelids
Animal: Segmented worms, internally and externally segmented, bilateral symmetry; examples: Leeches and earthworms
Phylum mollusks
Kingdom Animalia-Phylum consisting of mollusks,soft bodied animals with hard external shells
Phylum arthropoda
jointed appendages, hard exoskeleton, segmented body, waste eliminated through malphigian tubules
Phylum Echinodermata
radially symmetrical marine invertebrates including e.g. starfish and sea urchins and sea cucumbers
Phylum chordates
notochord and post-anal tail, dorsal hollow nerve cord, thyroid gland. Subphyla: Vertebrates, amphioxus, tunicates
Classes of chordate
amphibian, reptilia, aves, mammalia, osteichthyes, chondrichthyes
Class chondrichthyes
cartilaginous fish example: sharks, skates, and rays
Class osteichthyes (bony fish)
Have skeletons of bone, most have outer covering of scales, cold-blooded, one ventricle heart, the gills in the phayngeal slits are covered by flaps
Class amphibian
live in water with gills then land with lungs, thin, moist skin, 3 chambered heart, respiration through skin and lungs
example: frog, salamander, toad *
Class reptilia
reptiles; bony skeleton; dry, scaley skin; two pairs of limbs; leathery-shelled eggs; incompletely divided four-chambered heart; ex. turtle, alligator, snake, dinos *
Class aves
birds; bony skeleton; feathers; no teeth; wings; hard-shelled eggs; four-chambered heart; endothermic; lungs
Class mammalia
Mammals; bony skeleton; hairs; mammary glands in females secrete milk; four-chambered heart; lungs; ex. kangaroo(marsupial), platypus(monotreme), human(placental)
Monotremes
Mammals that have hair and mammary glands but reproduce by laying eggs.
Marsupials
Mammals whose immature offspring complete their development in an external pouch.
primates
Members of the order of mammals includes monkeys, apes, and humans
Parthenogenesis
process in which an unfertilized egg develops into a new individual
Types of asexual reproduction
binary fission, budding, fragmentation, vegetative reproduction, sopre formation
Fission
form of asexual reproduction in which an organism splits into two, and each half grows new parts to become a complete organism
Budding
asexual reproduction in which a part of the parent organism pinches off and forms a new organism
Fragmentation
A means of asexual reproduction whereby a single parent breaks into parts that regenerate into whole new individuals.
Testes
The male gonads, which produce sperm and secrete male sex hormones.
Vas deferens
a duct that carries spermatozoa from the epididymis to the ejaculatory duct
Prostate gland
exocrine gland, in men, at the base of the urinary bladder that secretes the fluid part of semen into the urethra during ejaculation
Scrotum
the external pouch that contains the testes
Urethra
duct through which urine is discharged in most mammals and which serves as the male genital duct
Ovary
the organ that bears the ovules of a flower
Oviduct (fallopian tube)
A pair of tubes that carries the egg from the ovary to the uterus.
Uterus
organ of the female reproductive system in which a fertilized egg can develop
Vagina
in the human female reproductive system, a canal that leads from the uterus to the outside of the body
Cervix
necklike opening to the uterus
Endometrium
(pregnancy) the mucous membrane that lines the uterus
Follicular phase
The first phase of the ovarian cycle, during which a follicle (an oocyte and its surroudning cells) enlarges and matures. This phase is under the control of FSH from the anterior pituitary, and typically lasts from day 1 to day 14 of the menstrual cycle. The follicle secretes estrogen during this time period.
Ovulation
the expulsion of an ovum from the ovary (usually midway in the menstrual cycle)
Luteal phase
The third phase of the ovarian cycle, during which a corpus luteum is formed from the remnants of the follicle that has ovulated its oocyte. The corpus luteum secretes progestrone and estrogen during this time period, which typically lasts from day 15 to day 28 of the menstrual cycle. Formation of the corpul luteum is triggered by the same LH surge that triggers ovulation, however in the absence of LH (levels quickly decline after the surge) the corpus luteum begins to degenerate.
Menstruation
phase of the menstrual cycle during which the lining of the uterus, along with blood and the unfertilized egg, is discharged through the vagina
hypothalamus
The hypothalamus is a portion of the diencephalon that lies just below the thalamus. It controls body temperature, appetite, sleep, sexual desire, and emotions such as fear. It also regulates the release of hormones from the pituitary gland and regulates the parasympathetic and sympathetic nervous systems.
Cleavage
The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane; specifically, the succession of rapid cell divisions without growth during early embryonic development that converts the zygote into a ball of cells.
Gastrulation
the process in which a gastrula develops from a blastula by the inward migration of cells
Gastrula
double-walled, or triple-walled stage of the embryo resulting from invagination of the blastula
layers of the gastrula
An embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesoderm, and endoderm.
Ectoderm
the outer germ layer that develops into skin and nervous tissue
Endoderm
the inner germ layer that develops into the lining of the digestive and respiratory systems
Mesoderm
the middle germ layer that develops into muscle and bone and cartilage and blood and connective tissue
Organogenesis
process of organ formation that takes place during the first two months of prenatal development
Embryonic membranes of the egg (bird embryos)
chorion, yolk sac, amnion, ** allantois
Chorion
membrane that contains the amniotic sac and fetus
Yolk sac
An embryonic structure particularly important in egg-laying animals because it contains the yolk, the only source of nutrients for the embryo developing inside the egg. IN humans, the yolk sac is very small (since mammals get their nutrients via the placenta) and is the site of synthesis of the first red blood cells.
Amnion
The innermost of four extraembryonic membranes; encloses a fluid-filled sac in which the embryo is suspended.
Allantois
the extraembyonic membrane of birds, reptiles and mammals that serves as an area of gaseous exchange and as a site for the storage of noxious excretion products
locomotion
the ability to move from place to place
sessile
describes an organism that remains attached to a surface for its entire life and does not move
hydrostatic skeleton
A fluid skeleton in many soft-bodied invertebrates, including annelids, that allows an organism to change shape but not volume. *
excretion
waste matter (as urine or sweat but especially feces) discharged from the body
ammonia
A small, very toxic molecule (NH3) produced by nitrogen fixation or as a metabolic waste product of protein and nucleic acid metabolism.
urea
major nitrogenous waste excreted in urine
uric acid
nitrogenous waste excreted in the urine
gastrovascular cavity
A central cavity with a single opening in the body of certain animals that functions in both the digestion and distribution of nutrients.
polyp
usually sessile stage of the life cycle of a cnidarian that has a cylindrical body with armlike tentacles
medusa
A cnidarian body plan characterized by a bowl shape and adapted for a free-swimming life.
cnidaria
Two-cell layered body with a digestive cavity surrounded by tentacles that sting prey. E.g. jellyfish, hydras, sea anemones.
cnidocytes
stinging cells
nematocysts
stinging cells that discharge when tentacles are touched
budding
an asexual process which part of a yeast cell pinches itself off to produce a small offspring cell
crop
in earthworms, part of the digestive system in which food can be stored; in birds, structure at the lower end of the esophagus in which food is stored and moistened
gizzard
muscular digestive system structure in which earthworms grind soil and organic matter * arthropods too
external respiratory surface
skin allows diffusion of oxygen and carbon dioxide, respiratory system of earthworms
aortic arches
hearts: each worm has 5 pairs (10 total) that pump blood
nephridia
excretory organ of an annelid that filters fliud in the coelom
malpighian tubules
An excretory organ that is unique to insects, empties into digestive tract and removes nitrogenous wastes from the hemolymph, also plays a role in osmoregulation.
open circulatory system
system in which blood is not always contained within a network of blood vessels
closed circulatory system
system in which blood is contained within a network of blood vessels
hemocoels
blood filled spaces found in open circulatory systems; sinuses
spiracles
openings in the abdomen of an insect that are used for breathing
tracheal tubes
network of breathing tubes that extend throughout the body of most terrestrial arthropods
digestion
the process by which the body breaks down food into small nutrient molecules
salivary amylase
in mouth, released by salivary glands and begins chemical breakdown of starch
epiglottis
a flap of cartilage that covers the windpipe while swallowing
pepsinogen
inactive form of pepsin
peptidases
intestinal enzyme that completes digestion of partially digested proteins to amino acids
villus
folded projection that increases the surface area of the walls of the small intestine
lacteal
A tiny lymph vessel extending into the core of an intestinal villus and serving as the destination for absorbed chylomicrons
bile
a substance produced by the liver that breaks up fat particles
egestion
the removal of nonsoluble waste materials
constipation
irregular and infrequent or difficult evacuation of the bowels
diarrhea
frequent and watery bowel movements
ulcers
open sores in the lining of the stomach or the small intestine generally associated with some kind of irritant or bacterial infection
alveoli
tiny sacs of lung tissue specialized for the movement of gases between air and blood
hemoglobin
iron-containing protein in red blood cells that carries oxygen for delivery to cells
respiration
the metabolic processes whereby certain organisms obtain energy from organic moelcules
artery
a blood vessel that carries blood away from the heart
vein
a blood vessel that carries blood from the capillaries toward the heart
capillary
microscopic blood vessel that carries blood between an artery and a vein, allowing the exchange of substances between the blood and interstitial fluid
plasma
the liquid part of blood
thromboplastin
an enzyme liberated from blood platelets that converts prothrombin into thrombin as blood starts to clot
prothrombin
plasma protein; converted to thrombin in the clotting process
thrombin
an enzyme that acts on fibrinogen in blood causing it to clot
fibrinogen
Plasma protein that is converted to fibrin in the clotting process
fibrin
The activated form of the blood-clotting protein fibrinogen, which aggregates into threads that form the fabric of the clot.
sinoatrial node
the heart's pacemaker, located in the wall of the right atrium
systolic
the blood pressure during that part of the heartbeat when the heart's ventricles are contracted and the blood is being pushed out into the arteries.
diastolic
indicating the arterial pressure during the interval *between heartbeats* (relaxation)
erythrocytes
red blood cells
leukocytes
White blood cells
thrombocytes
platelets
homeostasis
process by which organisms maintain a relatively stable internal environment
hormones
chemical messengers, mostly those manufactured by the endocrine glands, that are produced in one tissue and affect another
tropic hormones
hormones that stimulate other glands to release their hormones, TSH, ACTH, FSH, LH
hypothalamus
a neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion
positive feedback
A physiological control mechanism in which a change in some variable triggers mechanisms that amplify the change.
negative feedback
a mechanism of response in which a stimulus initiates reactions that reduce the stimulus
somatic nervous system
the division of the peripheral nervous system that controls the body's skeletal muscles
autonomic nervous system
the part of the nervous system of vertebrates that controls involuntary actions of the smooth muscles and heart and glands
reflex arc
sensory receptor, sensory neuron, motor neuron, and effector that are involved in a quick response to a stimulus
neuron
a cell that is specialized to conduct nerve impulses
resting potential
the potential difference between the two sides of the membrane of a nerve cell when the cell is not conducting an impulse
action potential
a neural impulse; a brief electrical charge that travels down an axon
threshold
the level of stimulation required to trigger a neural impulse
depolarization
the process during the action potential when sodium is rushing into the cell causing the interior to become more positive
repolarization
recharging of the myocardial cell from a contracted state back to a resting state
refractory period
the time after a neuron fires during which a stimulus will not evoke a response
neurotransmitter
transmits nerve impulses across a synapse
cones
neurons in the retina that are responsible for color vision
cornea
the clear tissue that covers the front of the eye
humor
any liquid or semi-liquid of the body, e.g. the aqueous or vitreous humor of the eyeball.
iris
diaphragm consisting of thin overlapping plates that can be adjusted to change the diameter of a central opening
lens
a transparent optical device used to converge or diverge transmitted light and to form images
pupil
contractile aperture in the iris of the eye
retina
the light-sensitive membrane covering the back wall of the eyeball
rods
retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond
auditory canal
the area that sound waves pass through to reach the eardrum
cochlea
a coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses
ear bones
hammer, anvil, and stirrup; transmit vibrations from eardrum to oval window
Eustachian tube
A narrow tube between the middle ear and the throat that serves to equalize pressure on both sides of the eardrum
oval window
membrane that covers the opening between the middle ear and inner ear
semicircular canal
one of three structures within the inner ear that help monitor the position of the body
tympanum
the membrane in the ear that vibrates to sound
excretion
waste matter (as urine or sweat but especially feces) discharged from the body
antidiuretic hormone
hormone secreted by the posterior pituitary gland to prevent the kidneys from expelling too much water
nephron
blood-filtering unit in the renal cortex of the kidney
glomerulus
little ball-shaped cluster of capillaries located at the top of each nephron
filtration
process by which fluid from the blood filters into Bowman's capsule in the kidneys
secretion
in the nephron, the movement of substances from the blood to the filtrate along the tubule. Secretion increases the rate at which substances can be removed from the body.
reabsorption
process in the kidney that puts useful substances (water, glucose, amino acids) back into the blood
smooth muscle
a muscle that contracts without conscious control and found in walls of internal organs such as stomach and intestine and bladder and blood vessels (excluding the heart)
cardiac muscle
muscle tissue found only in the heart
skeletal muscle
Vouluntary, striated muscle that moves bones, works in pairs and is attatched to bones by tendons
actin
protein that mainly makes up the thin filaments in striations in skeletal muscle cells
myosin
A protein present in muscle fibers that aids in contraction and makes up the majority of muscle fiber
semiconservative replication
Duplication of DNA resulting in two double helix molecules, each having one parental and one new strand **
griffith 1927
performed experiments with several different strains of bacterium; DISCOVERED THAT BACTERIA HAVE THE ABILITY TO TRANSFORM HARMLESS CELLS INTO VIRULENT ONCES BY TRANSFERRING SOME GENETIC FACTOR FROM ONE BACTERIA CELL TO ANOTHER (bacterial transformation; conducted the transformation experiment
avery, macleod, mccarty 1944
confirmed that DNA= the transformation factor from Griffith's experiments
meselon and stahl 1953
discovered DNA replicated semi- conservatively
telomeres
special nucleotide sequences at the end of DNA, do not contain genes, only prevent staggered ends of the daughter molecule from activating the cell's systems for monitoring DNA damage
telomerase
an enzyme in eukaryotic cells that can add telomeres to the ends of chromosomes after they divide
nitrogenous base
an organic base that contains nitrogen, such as a purine or pyrimidine; a subunit of a nucleotide in DNA and RNA
base pairing
principle that bonds in DNA can form only between adenine and thymine and between guanine and cytosine
DNA
deoxyribonucleic acid, the material that contains the information that determines inherited characteristics
RNA
ribonucleic acid, a natural polymer that is present in all living cells and that plays a role in protein synthesis
messenger RNA
RNA that copies the coded message from DNA in the nucleus and carries the message into the cytoplasm
transfer RNA
RNA in the cytoplasm that carries an amino acid to the ribosome and adds it to the growing protein chain
ribosomal RNA
type of RNA molecule that plays a structural role in ribosomes
transcription
process in which part of the nucleotide sequence of DNA is copied into a complementary sequence in RNA
translation
the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm
RNA processing
Modification of RNA transcripts, including splicing out of introns, joining together of exons, and alteration of the 5' and 3' ends.
exons
A coding region of a eukaryotic gene. Exons, which are expressed, are separated from each other by introns.
introns
Long segments of nucleotides that have no coding information
codon
three-nucleotide sequence on messenger RNA that codes for a single amino acid
anticodon
group of three bases on a tRNA molecule that are complementary to an mRNA codon.
operon
a group of genes that operate together
promoter
A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA.
mutations
changes in the genetic material
point mutation (base pair substitution)
a mutation in which only one nucleotide or nitrogenous base in a gene is changed
insertion
a mutation involving the addition of one or more nucleotide pairs to a gene
deletion
A mutational loss of one or more nucleotide pairs from a gene.
frameshift
A nucleotide is inserted or deleted, changing where the coding for entirely different amino acids.
aneuploidy
abnormal number of chromosomes
nondisjuction
the failure of homologous chromosomes to separate during meiosis I or the failure of sister chromatids to separate during mitosis or meiosis II
genome
the complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes, all the DNA in one cell of an organism
recombinant DNA
genetically engineered DNA made by recombining fragments of DNA from different organisms
genetic engineering
the technology of preparing recombinant DNA in vitro by cutting up DNA molecules and splicing together fragments from more than one organism
restriction enzymes
The proteins used to cut DNA molecules at specilic places so that scientists can isolate pieces with the desired genes.
recognition sites (sequences)
the specific sites on DNA that restriction enzymes cut
restriction fragments
DNA segment resulting from cutting of DNA by a restriction enzyme
gel electrophoresis
procedure used to separate and analyze DNA fragments by placing a mixture of DNA fragments at one end of a porous gel and applying an electrical voltage to the gel
polymerase chain reaction
technique that allows molecular biologists to make many copies of a particular gene
hershey and chase 1952
concluded that the genetic material of the bacteriophage was DNA, not protein
rosalind franklin 1950-53
carried out the X-ray crystallography analysis of DNA and showed DNA is a helix
watson and crick 1953
Figured out structure of DNA was a double helix
allele
one of the alternative forms of a gene that governs a characteristic, such as hair color
genotype
the genetic makeup of an organism
phenotype
The physical traits that appear in an individual as a result of its gentic make up.
test cross
the crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype
law of dominance
this states that some alleles are dominant and others are recessive
law of independent assortment
Mendel's second law, stating that each allele pair segregates independently during gamete formation; applies when genes for two characteristics are located on different pairs of homologous chromosomes.
law of segregation
members of a pair of homologous chromosomes separate during the formation of gametes and are distributed to different gametes so that every gamete receives only one member of the pair
incomplete dominance
a condition in which a trait in an individual is intermediate between the phenotype of the individual's two parents because the dominant allele is unable to express itself fully
codominance
inheritance pattern in which a heterozygote expresses the distinct traits of both alleles
multiple alleles
three or more alleles exist for a particular trait
polygenic traits
traits controlled by two or more genes
sex-linked traits
traits controlled by genes located on the X chromosome
hemophilia
sex-linked recessive disorder defined by the absence of one or more proteins required for blood clotting
sex-influenced trait
an autosomal trait that is influenced by the presence of male or female sex hormones
karyotype
A picture of all the chromosomes in a cell arranged in pairs
autosome
chromosome that is not a sex chromosome
pedigree
a diagram that shows the occurrence of a genetic trait in several generations of a family
mutations
changes in the nucleotide sequence of DNA
non-disjunction
meiosis in which there is a failure of paired homologous chromosomes to separate
polyploidy
condition in which an organism has extra sets of chromosomes
aneuploidy
A chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number
trisomy 21
condition in which an individual has three number 21 chromosomes, resulting in Down syndrome
mutations
changes in the genetic material
gene mutation
A change in the sequence of the bases in a gene, which changes the structure of the polypeptide that the gene codes for.
chromosomal mutation
mutation that occurs at the chromosomal level resulting in changes in the gene distribution to games during meiosis; caused when parts of chromosomes break off or rejoin incorrectly
deletion
loss of a piece of a chromosome due to breakage
translocation
change to a chromosome in which a fragment of one chromosome attaches to a nonhomologous chromosome
inversion
change to a chromosome in which a fragment of the original chromosome is reversed
PKU
A condition in which the body is unable to process and use a specific protein that is present in nearly all foods
cystic fibrosis
Hereditary condition that causes the exocrine glands to malfunction. The patient produces very thick mucus that causes severe congestion within the lungs and digestive system.
tay-sachs
recessive disorder, faulty lysosomes can't break down fat in the brain, motor problems
huntington's disease
A human genetic disease caused by a dominant allele; characterized by uncontrollable body movements and degeneration of the nervous system; usually fatal 10 to 20 years after the onset of symptoms.
klinefelter's syndrome
a chromosomal trisomy in which males have an extra X chromosome resulting in an XXy condition; affected individuals typically have reduced fertility
color-blindness
A sex-linked trait in which an individual cannot perceive certain colors.
bryophytes
A nonvascular plant that lives on the land; mosses, liverworts, and hornworts
tracheophytes
vascular plants
gymnosperms
seed plant that bears its seeds directly on the surfaces of cones.
angiosperms
flowering plants that produce seeds in fruit
monocotyledons
monocots- one cotyledon, , Angiosperms that have only one cotyledon in the seed. The veins in their leaves are parallel to each other and their flower parts are in groups of 3. Examples are corn, grass, wheat and lilies.
dicotyledons
class of anthophytes that have two cotyledons, reticulate leaf venation, and flower parts in multiples of four or five
stomates
the openings on the outside of a leaf which allows water to leave. These openings also allow CO2 to enter and oxygen to leave.
cutin
waxy covering in plants to prevent water loss
gametangia
A reproductive organ that houses and protects the gametes of a plant
sporopollenin
a durable polymer that covers exposed zygotes of charophyte algae and forms the walls of plant spores, preventing them from drying out.
meristem tissue
undifferentiated cells in the active growth regions of plants
apical meristem
Embryonic plant tissue in the tips of roots and in the buds of shoots that supplies cells for the plant to grow in length
zone of cell division
The zone of primary growth in roots consisting of the root apical meristem and its derivatives. New root cells are produced in this region.
zone of elongation
This is the region of the root tip adjacent to the zone of cell division. Cells sometimes elongate to more than ten times their original length.
zone of differentiation
zone of primary growth in roots where cells complete their differentiation and become functionally mature
lateral meristem
A meristem that thickens the roots and shoots of woody plants. The vascular cambium and cork cambium are lateral meristems.
roots
Absorbs water and minerals from the ground. Anchors plant in ground.
parenchyma cells
A relatively unspecialized plant cell type that carries out most of the metabolism, synthesizes and stores organic products, and develops into a more differntiated cell type.
casparian strip
A water-impermeable ring of wax around endodermal cells in plants that blocks the passive flow of water and solutes into the stele by way of cell walls
symplast
System of transport within a plant consisting of openings in cell walls called plasmodesmata
plasmodesmata
Open channels in the cell wall of a plant through which strands of cytosol connect from an adjacent cell. *see symplast
mycorrhizae
Mutualistic associations of plant roots and fungi.
rhizobium
symbiotic bacterium that lives in nodules on roots of specific legumes and fixes nitrogen gas from the air into a form of nitrogen plants require
taproot
primary root found in some plants that grows longer and thicker than other roots
adventitious roots
grow above ground and help support tall or long stems
aerial roots
roots that never touch the ground & take in moisture from the air
prop roots
Thick adventitious roots that grow from the lower part of the stem and brace the plant.
pith
soft spongelike central cylinder of the stems of most flowering plants
transpiration
loss of water from a plant through its leaves
guard cells
The two cells that flank the stomatal pore and regulate the opening and closing of the pore.
dermal tissue
outer covering or "skin" of a plant
vascular tissue
tissue that conducts water and nutrients through the plant body in higher plants
ground tissue
tissue between the dermal tissue and vascular tissue of a non-woody plant that functions in photosynthesis, storage, and support
trichomes
hairlike projections that extend from the epidermis and give the epidermis a fuzzy appearance
sclerenchyma cells
A rigid, supportive plant cell type usually lacking protoplasts and possessing thick secondary walls strengthened by lignin at maturity.
transpiration pull
when water evaporates from the leaves of a plant, water is pulled up to replace what was lost.
petals
modified leaves which are usually bright in color to attract pollinators.
sepal
A modified leaf in angiosperms that helps enclose and protect a flower bud before it opens.
pistils
female reproductive parts; found in center; made up of stigma, style, and ovary; stigma is sticky to catch pollen; style moves pollen to ovary
carpels
The ovule-producing reproductive organ of a flower, consisting of the stigma, style, and ovary.
ovary
the organ that bears the ovules of a flower
ovule
A structure that develops within the ovary of a seed plant and contains the female gametophyte.
style
the narrow elongated part of the pistil between the ovary and the stigma
stigma
sticky portion at the top of the style where pollen grains frequently land
stamen
the pollen-producing reproductive organ of a flower, consisting of an anther and a filament.
anther
the part of the stamen that contains pollen
filament
the stalk of a stamen
epicotyl
the portion of the stem of a plant embryo that is between the cotyledons and the first true leaves
hypocotyl
the part of a plant embryo directly below the cotyledons, forming a connection with the radicle.
radicle
An embryonic root of a plant.
gametophyte
the gamete-producing individual or phase in the life cycle of a plant having alternation of generations
sporophyte
the spore-producing individual or phase in the life cycle of a plant having alternation of generations
auxins
Stimulate stem elongation, root growth, branching, and cell differentiation
cytokinins
plant hormones that promote cell division
gibberellins
a growth hormone that causes a wide variety of effects. One role is to stimulate growth of stems by promoting cell division. Farmers use it to make fruit grow larger.
abscisic acid
plant hormone that inhibits cell growth, prevents premature germination, and stimulates closing of the stomata
ethylene
plant hormone that stimulates fruits to ripen
tropism
A growth response of a plant toward or away from a stimulus
ATP
(adenosine triphosphate) main energy source that cells use for most of their work
cristae
An infolding of the inner membrane of a mitochondrion that houses the electron transport chain and the enzyme catalyzing the synthesis of ATP.
matrix
the surface area exposed to fluids, where the production of energy takes place, in a mitochondrion
anaerobic
describes a process that does not require oxygen
aerobic
process that requires oxygen
glycolysis
first step in releasing the energy of glucose, in which a molecule of glucose is broken into two molecules of pyruvic acid
krebs cycle
second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions, in the mitochondrial matrix
anaerobic respiration (fermentation)
Form of cellular respiration in which some decomposers get the energy they need through the breakdown of glucose (or other nutrients) in the absence of oxygen. Compare aerobic respiration; eg: production of ethyl alcohol by yeast deprived of air
alcohol fermentation
The conversion of pyruvate to carbon dioxide and ethyl alcohol.
lactic acid fermentation
Series of anaerobic chemical reactions in which pyruvic acid uses NADH to form lactic acid and NAD+, which is then used in glycolysis; supplies energy when oxygen for aerobic respiration is scarce
electron transport chain
a series of molecules, found in the inner membranes of mitochondria and chloroplasts, through which electrons pass in a process that causes protons to build up on one side of the membrane
acetyl-coA
Acetyl coenzyme A; the entry compound for the citric acid cycle in cellular respiration, formed from a fragment of pyruvate attached to a coenzyme.
energy carriers
NADH FADH2, Molecules specialized for receiving, storing, and delivering energy within the cell.
pyruvate
Organic compound with a backbone of three carbon atoms. Two molecules form as end products of glycolysis
chemiosmosis
A process for synthesizing ATP using the energy of an proton gradient and the ATP synthase enzyme.
proton gradient
a gradient formed by the difference in proton concentrations across a membrane
ATP synthase
large protein that uses energy from H+ ions to bind ADP and a phosphate group together to produce ATP
redox reactions
A chemical reaction involving the transfer of one or more electrons from one reactant to another; also called oxidation-reduction reaction.
oxidation
The loss of electrons from a substance involved in a redox reaction.
reduction
The addition of electrons to a substance involved in a redox reaction.
oxidative phosphorylation
The production of ATP using energy derived from the redox reactions of an electron transport chain.
photosynthesis
process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches
thylakoids
A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.
stroma
The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
grana
A stacked portion of the thylakoid membrane in the chloroplast. Grana function in the light reactions of photosynthesis
photolysis
A reaction taking place in the thylakoid membranes of a chloroplast during light-dependant reactions where two molecules of water are split to form oxygen, hydrogen ions, and electrons
calvin cycle
The second of two major stages in photosynthesis (following the light reactions), involving atmospheric CO2 fixation and reduction of the fixed carbon into carbohydrate.
palisade layer
The tightly packed photosynthetic cell found just under the epidermus in many leaves.
spongy layer
lower portion in a leaf, irregular shaped, chloroplast- filled cells and separated by air spaces
guard cells
specialized cell in the epidermis of plants that controls the opening and closing of stomata by responding to changes in water pressure
photosystems
clusters of chlorophyll within the thylakoid membrane that absorb light energy
light reaction
the first stage of photosynthesis during which energy from light is used for the production of ATP
dark reaction
the second stage of photosynthesis that starts with ATP, NADPH, and Carbon dioxide and produces glucose
rubisco
enzyme that converts inorganic carbon dioxide molecules into organic molecules during the final step of the calvin cycle
stomata
the small openings on the undersides of most leaves through which oxygen and carbon dioxide can move
sister chromatids
two daughter strands of a replicated chromosome joined at the middle by a centromere
centromere
the region of the chromosome that holds the two sister chromatids together during mitosis
tetrad
the four chromatids in a pair of homologous chromosomes that come together as a result of synapsis during meiosis
interphase
period of the cell cycle between cell divisions, G1, S (DNA replication), G2
mitosis
in eukaryotic cells, a process of cell division that forms two new nuclei, each of which has the same number of chromosomes
prophase
first and longest phase of mitosis, during which the chromosomes become visible and the centrioles separate and take up positions on the opposite sides of the nucleus
metaphase
second phase of mitosis, during which the chromosomes line up across the center of the cell
anaphase
the third phase of mitosis, during which the chromosome pairs separate and move toward opposite poles
telophase
the final stage of mitosis or meiosis, during which a nuclear membrane forms around each set of new chromosomes
meiosis
(genetics) cell division that produces reproductive cells in sexually reproducing organisms
crossing over
process in which homologous chromosomes exchange portions of their chromatids during meiosis
cytokinesis
division of the cytoplasm during cell division
cleavage furrow
The first sign of cleavage in an animal cell; a shallow groove in the cell surface near the old metaphase plate.
cell plate
A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis.
middle lamella
A thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young plant cells. *
synapsis
the side by side pairing of homologous maternal and paternal chromosomes at the start of meiosis
spindle fibers
protein structures which move the chromosomes during cell division. * kinetochore
reduction division
(genetics) cell division that produces reproductive cells in sexually reproducing organisms
homologous chromosomes
chromosomes that have the same sequence of genes, that have the same structured, and that pair during meisosis
cell cycle
The regular sequence of growth and division that cells undergo.
nondisjuction
the failure of homologous chromosomes to separate during meiosis I or the failure of sister chromatids to separate during mitosis or meiosis II
Metabolism
all of the chemical reactions that occur within an organism
Plasma membrane
thin flexible barrier that regulates what enters and exits the cell; composed of two layers of lipids
Cytoplasm
a jellylike fluid inside the cell in which the organelles are suspended
Prokaryotic
describes a cell that does not have a nucleus or anyother membrane-covered organelles; also called bacteria.
Eukaryotic
A cell characterized by the presence of a nucleus and other membrane-bound organelles. Eukaryotes can be unicellular (protists) or multicellular (fungi, plants and animals).
Organelles
specialized structure that performs important cellular functions within a eukaryotic cell
Nucleus
a part of the cell containing DNA and RNA and responsible for growth and reproduction
Nucleolus
The organelle where ribosomes are made, synthesized and partially assembled, located in the nucleus
Nuclear envelope
double membrane perforated with pores that control the flow of materials in and out of the nucleus
Cytoskeleton
a network of fibers that holds the cell together, helps the cell to keep its shape, and aids in movement
Centrioles
Located near the nucleus and help to organize cell division
Cilia
short, hair-like structures made of microtubules that enable movement of cells or movement of materials outside a cell
Flagella
long, thin, whip-like structures, with a core of microtubules, that enable some cells to move
Chromatin
material consisting of DNA and proteins; visible as individual chromosomes in a dividing cell
Endoplasmic reticulum
a cell structure that forms a maze of passageways in which proteins and other materials are carried from one part of the cell to another
Ribosomes
site of protein synthesis
Golgi apparatus
Organelle that modifies, sorts, and packages proteins from the endoplasmic reticulum and send proteins to their final destination
Vesicles
small membrane sacs that specialize in moving products into, out of, and within a cell.
Vacuoles
saclike structures that store materials such as water, salts, proteins, and carbohydrates
Lysosomes
cell organelle filled with enzymes needed to break down certain materials in the cell
Mitochondria
Powerhouse of the cell, organelle that is the site of ATP (energy) production
Chloroplast
an organelle found in plant and algae cells where photosynthesis occurs
Plastid
group of plant organelles that are used for storage of starches, lipids, or pigments
Endosymbiosis
Process through which early prokaryotic cells are thought to have engulfed other, smaller cells and eventually incorporated them as organelles; these cells evolved into modern-day eukaryotes.
Membrane protein/channel
a membrane embedded in the plasma membrane that mediates the passage of certain molecules
Fluid mosaic model
The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids.
Cell wall
strong supporting layer around the cell membrane in plants, algae, and some bacteria
Diffusion
process by which molecules tend to move from an area where they are more concentrated to an area where they are less concentrated
Passive transport
the movement of substances across a cell membrane without the use of energy by the cell
Osmosis
diffusion of water through a selectively permeable membrane
Active transport
energy-requiring process that moves material across a cell membrane against a concentration difference
Hypertonic solution
a solution that has a higher concentration of solute outside than inside a cell, causing water to leave the cell by osmosis *
Hypotonic solution
in cells, solution in which the concentration of dissolved substances is lower in the solution outside the cell than the concentration inside the cell; causes a cell to swell and possibly burst as water enters the cell *
Isotonic solution
a solution in which the concentration of solutes is essentially equal to that of the cell which resides in the solution
Solvent
the substance in which the solute dissolves
Solute
substance that is dissolved in a solvent to make a solution
Apoptosis
cell death
Leucoplasts
plant organelle used to store starch
Chromoplasts
organelles that contain pigments used in photosynthesis
Stroma
The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
Grana
A stacked portion of the thylakoid membrane in the chloroplast. Grana function in the light reactions of photosynthesis
Mictrotubules
hollow structure made of proteins and play a role in maintaining call shape.
Microfilaments
Long, thin fibers that function in the movement and support of the cell
Cytosol
the aqueous part of the cytoplasm within which various particles and organelles are suspended
Plasmolysis
when a cell is in a hypertonic environment, the cell will lose water to its surroundings, shrink, and its plasma membrane will pull away from the wall
Turgor
a cell's swelling against its cell wall caused by the pressure of the cell's contents
Exocytosis
process by which a cell releases large amounts of material
Endocytosis
the process by which a cell membrane surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell
Pinocytosis
process by which a cell takes in liquid from the surrounding environment
Pseudopods
temporary extension of a cell's cytoplasm and plasma membrane; used by certain protozoans in movement and feeding.
Receptor-mediated endocytosis
The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances.
Ingestion
process of taking in food
Digestion
the breaking down of food into nutrients the body can use. the digestive system is a series of body organs that break foods down and absorb their nutrients
Respiration
the metabolic processes whereby certain organisms obtain energy from organic moelcules
Transport
an exchange of molecules (and their kinetic energy and momentum) across the boundary between adjacent layers of a fluid or across cell membranes
Regulation
the ability of an organism to respond to a change in its surroundings
Synthesis
a chemical reaction in which two or more simple substances combine to form a new, more complex substance
Excretion
the process of removing wastes from the body
Egestion
the removal of indigestible material
Reproduction
the production of offspring
Irritability
the ability to respond to a stimulus
Locomotion
the ability to move from place to place
Metabolism
set of chemical reactions through which an organism builds up or breaks down materials as it carries out its life processes
Compound microscope
light microscope that has two converging lens systems: the objective and the eyepiece
Phase contrast microscope
emphasizes differences in specimen's capacity to bend light waves; good for viewing living cells; up to 1,500x
Transmission electron microscope
An electron microscope used to study the internal structure of thin sections of cells
Ultracentrifuge
a high speed centrifuge used to determine the relative molecular masses of large molecules in high polymers and proteins
cell fractionation
technique in which cells are broken into pieces and the different cell parts are separated
Freeze fracture
splits a membrane along the middle of the phospholipid bilayer. When a freeze-fracture preparation is viewed with an electron microscope, protein particles are interspersed in a smooth matrix, supporting the fluid mosaic model.
Tissue culture
a technique in which biologists grow large amounts of a single kind of cell
Anton van leeuwenhoek
father of microscopy-developed powerful microscopes-first to see and write about bacteria, years plants, living organisms in drop of water and circulation of blood corpuscles in capillaries
Robert hooke
first to observe "small chambers" in cork and call them cells.
Matthias schleiden
German physiologist and histologist who in 1838 formulated the cell theory (1804-1881)
Theodor schwann
German physiologist and histologist who in 1838 and 1839 identified the cell as the basic structure of plant and animal tissue (1810-1882)
Rudolf virchow
German pathologist who recognized that all cells come from cells by binary fission and who emphasized cellular abnormalities in disease (1821-1902)
element
substance consisting entirely of one type of atom
proton
positively charged particle
neutron
neutral particle of an atom
electron
negatively charged particle
atomic number
the number of protons in the nucleus of an atom
isotope
atoms of the same element that have different numbers of neutrons
ionic bond
a chemical bond in which one atom loses an electron to form a positive ion and the other atom gains to electron to form a negative ion
covalent bond
a bond formed when atoms share one or more pairs of electrons
molecule
the simplest structural unit of an element or compound
polar molecule
molecule with an unequal distribution of charge, resulting in the molecule having a positive end and a negative end
hydrogen bond
weak chemical bond formed by the attraction of positively charged hydrogen atoms to other negatively charged atoms
non-polar molecule
molecule that shares electrons equally and does not have oppositely charged ends
hydrophobic
Repelling, tending not to combine with, or incapable of dissolving in water.
hydrophilic
Having an affinity for water; readily absorbing or dissolving in water.
pH
a value that indicated the acidity or alkalinity of a solution on a scale of 0-14, based on the proportion of H+ ions.
acid
A substance that increases the hydrogen ion concentration of a solution.
base
compound that produces hydroxide ions (OH+) in solution
buffer
an ionic compound that resists changes in its pH
acid rain
rain that contains more acid than normal
hydrocarbon chain
chain of carbon atoms bonded to each other and to hydrogen atoms, tail of a fatty acid *
organic compound
A compound that contains carbon
carbohydrate
compound made up of carbon, hydrogen, and oxygen atoms; major source of energy for the human body
monomer
a simple compound whose molecules can join together to form polymers
isomer
Organic compounds that have the same molecular formula, but different structural formulas
monosaccharide
a simple sugar that is the basic subunit of a carbohydrate
disaccharide
A double sugar, consisting of two monosaccharides joined by dehydration synthesis.
dehydration synthesis
A chemical reaction in which two molecules covalently bond to each other with the removal of a water molecule.
hydrolysis
Breaking down complex molecules by the chemical addition of water
polysaccharide
long polymer chain made up of simple sugar monomers
lipid
macromolecule made mainly from carbon and hydrogen atoms; includes fats, oils, and waxes
glycerol
with fatty acids, make up the building blocks of lipids *
fatty acid
with glycerol, make up the building blocks of lipids
saturated fat
fat in which all three fatty acid chains contain the maximum possible number of hydrogen atoms
unsaturated fat
A lipid made from fatty acids that have at least one double bond between carbon atoms, fat with less than the maximum number of hydrogens in one or more of its fatty acid chains
protein
macromolecule that contains carbon, hydrogen, oxygen, and nitrogen; needed by the body for growth and repair and to make up enzymes
enzyme
A macromolecule serving as a catalyst, a chemical agent that changes the rate of a reaction without being consumed by the reaction.
polymer
large compound formed from combinations of many monomers
peptide bond
covalent bond formed between amino acids
energy of activation
The amount of energy that reactants must absorb before a chemical reaction will start, enzymes act by reducing the energy of activation
induced fit
The interaction between a substrate molecule and the active site of an enzyme, which changes shape slightly to embrace the substrate and catalyze the reaction.
substrate
the substance acted upon by an enzyme or ferment
active site
the site on an enzyme that attaches to a substrate
coenzyme
An organic molecule serving as a cofactor. Most vitamins function as coenzymes in metabolic reactions. * see cofactor
cofactor
ion or molecule that must bind to the enzyme before substrates can also bind; without cofactor enzyme is intact but nonfuctional * see conenzyme
nucleic acid
an organic compound, either RNA or DNA, whose molecules are made up of one or two chains of nucleotides and carry genetic information, macromolecule containing hydrogen, oxygen, nitrogen, carbon, and phosphorus
nucleotide
monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base, * see a diagram -- building blocks of DNA
purine
an organic molecule that has a double ring of carbon and nitrogen atoms, adenine and guanine
pyrimidine
single-ring nitrogenous base, found in DNA and RNA; either cytosine, thymine, or uracil
DNA
deoxyribonucleic acid; a complex molecule containing the genetic information that makes up the chromosomes
RNA
ribonucleic acid, a natural polymer that is present in all living cells and that plays a role in protein synthesis
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