Unformatted text preview: Chapter 6 Learning Outcomes The Role of Cell Division Explain how cell division functions in reproduction, growth, and repair: Mitosis causes growth and
repair by providing more identical cells to replace old, damaged or missing cells for repair or to produce
more tissue for growth. It also helps with reproduction by creating haploid cells to form zygotes for
reproduction. Describe the structural organization of a prokaryotic vs. eukaryotic genome: Prokaryotic genomes are
found in a single strand of DNA in a circular shape. Eukaryotic are packed into chromosomes in a double
helix shape. Describe the major events of eukaryotic cell division that enable the genome of one cell to be passed
on to two daughter cells: In cell division, the S phase ensures that all 46 chromosomes are duplicated
for the cell to give to each daughter cell. G2 phase checks them for error, and then mitosis happens in
which the cell divides to give each daughter cell the same genome. Explain prokaryotic cellular division (binary fission) and the production of clones via asexual
reproduction: Prokaryotes (bacteria and archaea) reproduce by binary fission. The chromosome
replicates (beginning at the origin of replication) and the two daughter chromosomes actively move
apart. Essentially cloning themselves then separating. Since prokaryotes evolved before eukaryotes,
mitosis probably evolved from binary fission. Certain protists exhibit types of cell division that seem
intermediate between binary fission and mitosis. The following terms (and be able to diagram a cell with)
o Genome: complete genetic information of an organism
o Haploid: Haploid cells have half the number of chromosomes as diploid (haploid cell contains
only one complete set of chromosomes). They reproduce via Meiosis, and two haploid cells
merge together during fertilization. Haploid cells are used in sexual reproduction, sperm and
ova (also known as Gametes).
o Diploid: Diploid cells contain two complete sets (2n) of chromosomes. They reproduce via
Mitosis by making daughter cells that are exact replicas. Diploid cells are found in skin, blood, &
muscle cells (also known as somatic cells).
o Somatic cells: skin, muscle, etc. Are diploid and have 2 sets (2n) of chromosomes. Human skin
cell has 46 chromosomes
o Gametes: Egg and sperm cells. They are haploid. Have 1 set ("n") of chromosomes. Humans
have 23 different chromosomes
o Homologous chromosomes: set of one maternal and one paternal chromosomes that pair up
with each other inside a cell during meiosis.
o Mitosis: cell division of the nucleus that preserves the original parental number of
chromosomes in the 2 daughter cells
o Cytokinesis: division of the cytoplasm
o Spindle apparatus: A system of fibers which go from one end of the cell to the other
o Kinetochores: complex of proteins attaching the centromeres of sister chromatids to spindle
o Binary fission: is the process that bacteria & archaea use to carry out cell division o Asexual reproduction: is a type of reproduction by which offspring arise from a single organism,
and inherit the genes of that parent only
o Sister chromatids: joined copies of the original chromosomes. They each contain an identical
DNA molecule and are attached by cohesins.
o Centromere: is the narrow “waist” of the duplicated chromosome, where the two chromatids
are most closely attached.
o Centrosomes: is an organelle that serves as the main microtubule organizing center (MTOC) of
the animal cell as well as a regulator of cell-cycle progression.
o Microtubules: are a component of the cytoskeleton. They are found throughout the cytoplasm.
They are also involved in chromosome separation (mitosis & meiosis) and are the major
constituents of mitotic spindles, which are used to pull apart eukaryotic chromosomes.
o Daughter Cells: two cells that are the result of division from a parent cell
o Gene: a sequence of DNA or RNA, which carries hereditary information and codes for the
function of a cell.
o Allele: different versions of the same kind of gene on a pair of homologous chromosomes o
Eukaryotic cell cycle
o Interphase and its sub-phases, including events within phases of division of the genome
(mitosis), including characteristic events within division of the cytoplasm (cytokinesis): o o
Interphase Sub-phases: G1 phase (first gap): all cellular contents of the cell, excluding the chromosomes are duplicated.
The cell grows, ensures it has enough nutrients, and space. S phase (synthesis): duplication of chromosomes occurs. G2 phase (second gap): cell double checks for error and ensure the chromosomes were
duplicated properly. After receiving the ‘ok’ signal, Mitosis occurs, and then cytokinesis.
Mitotic Phases: Prophase & Prometaphase: chromatin condense to form chromosomes and the nuclear
envelope disappears. Metaphase: chromosomes line up into the middle of the cell, and spindle fibers attach to them. Anaphase: the chromosomes are pulled apart giving each new daughter cell a copy of the
original genome. Telophase & Cytokinesis: new nuclear envelope forms, chromosomes unfold back into
chromatin, nucleoli reappear, cell continues to elongate. Cytokinesis is well underway.
- Cytokinesis in animals, the cell splits into two with a cleavage furrow. In plants, a cell
plate forms in between the splitting cells. Regulation of the cell cycle (control system)
o The three checkpoints, including cyclin, Cdks, and MPF in the cell cycle control system: Cyclin
is a regulatory protein that a Cyclin dependent kinase (CDK) much be attached to. The
maturation promoting factors give the go ahead signals at the checkpoints after the cell has
been checked. MPF (maturation-promoting factor) is a cyclin-Cdk complex that triggers a cell’s
passage past the G2 checkpoint into the M phase.
o The role of the checkpoints: The checkpoints in the cell cycle, ensure that there are no errors or
mistakes in each part of the cycle. Explain how the abnormal cell division of cancerous cells escapes normal cell cycle controls: They
ignore checkpoints and signals and keep dividing without any regulation. Because of this an
overabundance of cells is created and tumors may appear, which can cause cancer. o o
o Chapter 7 Learning Outcomes o
o The Basis of Heredity
Explain in general terms how traits are inherited from parents to offspring: Gametes transmit genes.
During fertilization, male and female gametes unite, therefore passing on genes to the offspring. Distinguish between asexual and sexual reproduction and describe their respective advantage:
Asexual reproduction is when an offspring can be produced by one parent, and they inherit the genetic
information from that one parent. Sexual reproduction occurs when two parents produce an offspring
and the offspring receive genetic information from both parents. Describe how the chromosome number changes throughout the human life cycle: For successful
reproduction an egg gamete (n) must be fertilized by sperm gamete (n). When the two haploid cells
(sperm + egg) are fertilized, it becomes a zygote (diploid) with 2n genomic content. Humans are diploid
organisms, and we produce haploid cells only during reproductive cycles to create offspring. Explain how haploid and diploid cells differ from each other- state which cells in the human body are
diploid and which are haploid: The process and phases of Meiosis
o Location of meiosis: sex cells. Sperm cells in males, egg cells in females.
o Uniqueness of cells produced via meiosis: four genetically unique cells are produced.
Describe three events that occur during Meiosis I but not during Mitosis
o Synapsis of homologous chromosomes and crossing over of non-sister chromatids:
Homologous chromosomes physically connect and exchange genetic information
o Independent assortment of homologous chromosome tetrads: At the metaphase plate, there
are paired homologous chromosomes (tetrads), instead of individual replicated chromosomes
o Separation of homologous chromosomes: At anaphase I, it is homologous chromosomes,
instead of sister chromatids, that separate Sources of variability in offspring due to mating: mate selectivity, one set of chromosomes from both
parents more genetic variety
Explain how independent assortment, crossing over, and random fertilization contribute to genetic
variation in sexually reproducing organisms: Independent assortment is the random lining up of the homologues during metaphase I of meiosis I. Each pair of chromosomes sorts maternal and paternal homologues into daughter cells independently of the other pairs.
Crossing over (occurs early during prophase I of meiosis I) involves the switching of genes between the nonsister chromatids of homologues which allows for mixture of maternal and paternal genetic material with new, recombinant chromosomes. Contributes to genetic variation by combining DNA from two parents into a single chromosome.
Random fertilization adds to genetic variation because any sperm can fuse with any ovum (unfertilized egg). The fusion of two gametes (each with 8.4 million possible chromosome combinations from independent assortment) produces a zygote with any of about 70 trillion diploid combinations. Crossing over adds even more variation.
Describe potential errors of meiosis that lead to abnormal chromosome number and/or changes in
o Euploidy: increase in number of complete sets of chromosome occurs frequently in plants,
rarely in animals
can lead to formation of new species.
o Polyploidy: The presence of extra chromosome sets (does not imply unbalanced chromosome
sets / aneuploidy) o Aneuploidy: variation in the number of a particular chromosome within a set generally leads to
an abnormal condition because it leads to an imbalance in amount of gene products (too much
or too little)
o Monosomy: Cells of the enbryo contain 45 chromosomes instead of 46
o Trisomy: Cells of the embryo contain 47 chromosomes instead of 46
o Barr body: Dark, staining, inactive X chromosome in the cell's nucleus of females
o X-chromosome inactivation: one of the copies of the X chromosome present in female
mammals is inactivated
o Changes in chromosome structure: likely result in defects
o Deletions: Segment of the chromosome is deleted
o Inversions: Segment of the chromosome is inverted
o Translocations: Entire piece of a chromosome may break off and reattach to a different
o Duplications: Piece of the chromosome is duplicated o
o Chapter 9 Learning Outcomes o
Explain why DNA in one cell contains the blueprint for every cell in a eukaryote:
o DNA is called the blueprint of life because it contains the instructions needed for an organism to
grow, develop, survive and reproduce. DNA does this by controlling protein synthesis. Proteins do
most of the work in cells, and are the basic unit of structure and function in the cells of
organisms. Describe the structure of the DNA double helix, including:
o The basic structure of a nucleotide: Nucleotides consist of a phosphate group, a ribose sugar, and
a nitrogenous base. Each nucleotide is named for the 5-carbon sugar it contains (Adenine &
Thymine, Cytosine & Guanine).
o Complementary base pairing rules: Adenine & Thymine, Cytosine & Guanine.
o Sugar-phosphate backbone:
o Antiparallel nature of the two strands of DNA: Describe the structure of RNA, including:
o The different kinds of RNA (mRNA, tRNA, rRNA) and their cellular roles:
-mRNA: carries DNA gene information to the ribosome (linear shaped)
-tRNA: brings amino acids to the ribosome (clover leaf shaped)
-rRNA: is part of the structure of ribosomes (sphere shape, like ball of yarn)
o The similarities and differences between DNA and RNA:
DNA (deoxyribonucleic acid)- Has two strands, a dioxyribose backbone, and the nitrogenous base
thymine (T) instead of uracil (U). It is the cells “blueprint”.
RNA (ribonucleic acid)- Has one strand, a sugar ribose backbone, and the nitrogenous base uracil
(U) instead of thymine (T). Outline the general features of prokaryotic and eukaryotic chromosomes, including how they are
packaged into a cell: Most prokaryotes contain a single, circular chromosome that is found in an area in
the cytoplasm called the nucleoid.
o DNA is a working molecule; it must be replicated when a cell is ready to divide, and it must be
“read” to produce the molecules, such as proteins, to carry out the functions of the cell.
o The DNA helix is wrapped around proteins to form nucleosomes. The protein coils are further
coiled, and during mitosis and meiosis, the chromosomes become even more greatly coiled to
facilitate their movement. Describe the process of DNA replication, including:
o The major enzymes, molecules and structures involved.
Helicase - Uses the hydrolysis of ATP to "unzip" or unwind the DNA helix at the replication fork to
allow the resulting single strands to be copied.
Primase - Polymerises nucleotide triphosphates in a 5' to 3' direction. The enzyme synthesises
RNA primers to act as a template for future Okazaki fragments to build on to. DNA Polymerase III - synthesizes nucleotides onto the leading end in the classic 5' to 3' direction.
DNA Polymerase I - synthesizes nucleotides onto primers on the lagging strand, forming Okazaki
fragments. However, this enzyme cannot completely synthesize all of the nucleotides.
Ligase - "glues" together Okazaki fragments, an area that DNA Pol I is unable to synthesize.
Telomerase - Catalyzes the lengthening of telomeres; the enzyme includes a molecule of
RNA that serves as a template for new telomere segments.
Topoisomerase - introduces a single-strand nick in the DNA, enabling it to swivel and
thereby relieve the accumulated winding strain generated during unwinding of the double helix.
Single Strand Binding Proteins - Responsible for holding the replication fork of DNA open while
polymerases read the templates and prepare for synthesis.
o Continuous and discontinuous replication.
Continuous replication happens along the leading strand in the 5’ to 3’ direction.
Discontinuous replication is along the lagging strand and is synthesized in Okazaki fragments.
o The semi-conservative nature of DNA replication: when DNA is duplicated, each new double
strand consists of one parental strand and one new daughter strand.
5’ to 3’ synthesis: is the direction of replication because DNA polymerase enzymes can only catalyze a
reaction that joins a free deoxyribonucleotide (A, T, C, or G) to a growing strand if there is a free 3 ′ end,
with a free 3′-OH group. That means that the growing strand always has to be oriented in the 5 ′-3 ′
direction. Template vs. coding strand: The difference between the coding strand and non-coding strand is noncoding strand is called template strand which does not code for mRNA whereas the coding stand codes
for mRNA which is further used for transcription and translation. The codes are coded in a definite
pattern A-U,G-C for RNA and A-T,G-C, for DNA. Be familiar with the sequence of replication and the following components. Be able to label a diagram
of DNA replication with these terms:
o DNA polymerase: an enzyme that synthesizes a new strand of DNA complementary to a template
o Helicase: an enzyme that helps to open up (unzip) the DNA helix during DNA replication by
breaking the hydrogen bonds
o Primase: Polymerises nucleotide triphosphates in a 5' to 3' direction. The enzyme synthesises
RNA primers to act as a template for future Okazaki fragments to build on to.
o Ligase: the enzyme that catalyzes the joining of DNA fragments together DNA
o Primers: a short stretch of RNA nucleotides that is required to initiate replication and allow DNA
polymerase to bind and begin replication
o Origin of replication: Site where the replication of a DNA molecule begins
o Replication fork: the Y-shaped structure formed during the initiation of replication
o Leading strand: the strand that is synthesized continuously in the 5' to 3' direction that is
synthesized in the direction of the replication fork
o Lagging strand: during replication of the 3' to 5' strand, the strand that is replicated in short
fragments and away from the replication fork o Okazaki fragment: the DNA fragments that are synthesized in short stretches on the lagging
o Direction of replication: occurs on the ‘5 to 3’ strand
o Telomeres: the DNA at the end of linear chromosomes
o Telomerase: an enzyme that contains a catalytic part and an inbuilt RNA template; it functions to
maintain telomeres at chromosome ends Identify the major differences in DNA replication between prokaryotes and eukaryotes and how they
o 1) Prokaryotic DNA is found in the nucleoid and replication happens in the cytoplasm. Eukaryotic
DNA is found in the nucleus and is replicated there.
o 2) Prokaryotes mostly replicate DNA through binary fission. Cell division for eukaryotes is much
more complex, and replication happens during the synthesis phase of the cell cycle.
o 3) Prokaryotes are organized in circular chromosomes, Eukaryotes as linear chromosomes.
o 4) Prokaryotes have a single point of origin, Eukaryotes have multiple points of origin.
o 5) Prokaryotes can replicate nucleotides at a much quicker rate (1000 nucleotides/s), Eukaryotes
replicate more slowly due to their complexity (50-100 nucleotides/s).
o 6) Telomerase is only found in eukaryotic replications. Understand the concept of the flow of genetic information (the Central Dogma), and the role of
different chemical “languages” (nucleotides, amino acids) in this process: DNA RNA Proteins
Describe transcription, including the major enzymes and molecules involved:
Initiation: RNA polymerase binds to the promoter, the DNA molecule is unwound and strands are
separated at the beginning of the gene sequence, separating the double helix near the promoter.
o Elongation: RNA polymerase travels along the DNA template strand, unwinding the double helix
and adding complimentary RNA nucleotides along the template strand. As the mRNA strand
leaves the DNA strands, the helix re-forms.
o Termination: RNA polymerase reaches a termination sequence, releases the completed mRNA
strand, and detaches from the DNA. The RNA polymerase is then free to bind to the promoter
region of another gene and to synthesize another RNA molecule.
Be able to transcribe a DNA template into RNA: see handout for diagram. Understand the concept of the genetic code: it translates the sequence of bases in nucleic acids into the
sequence of amino acids in proteins. Describe translation, including the roles of mRNA, tRNA, rRNA and ribosomes, including what is occurring
during the phases of transcription: initiation, elongation, & termination: see handout for diagram.
Translation is the process carried out in the ribosome where the information encoded in mRNA is used to
produce a protein (it occurs on the surface of the ribosome). Messenger RNA (mRNA) carries DNA gene information to the ribosome.
o Transfer RNA (tRNA) brings amino acids to the ribosome.
o Ribosomal RNA (rRNA) is part of the structure of ribosomes. rRNA combines with proteins to
form ribosomes; the small subunit binds mRNA; the large subunit binds tRNA and catalyzes
peptide bond formation between amino acids during protein synthesis.
Initiation (step 1):
1. A preinitiation complex forms, consisting of the small ribosomal subunit and a methionine tRNA
o 2. The UAC anticodon of the methionine tRNA binds the AUG start codon in the mRNA.
o 3. The large ribosomal subunit attaches to the small subunit,
Elongation (step 2):
4. A second tRNA anticodon base-pairs with the second codon on the mRNA
5. The catalytic site of the large subunit breaks the bond holding methionine to its tRNA and
forms a peptide bond between this amino acid and the amino acid attached to the second tRNA
6. The “empty” tRNA is released and the ribosome moves down the mRNA one codon. The tRNA
with the growing amino acid chain is now in the ribosome’s first binding site, and the...
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