Genetics

Terms Definitions
Artificial Selection
Purposeful matings to keep scientific wanted traits for generations
Belyaev
1950s. Domesticated foxes were selected and bred. Argressive vs domesticated foxes.
Gregor Mendel
1822-1884. Experimented with pea plants and is known as the father of genetics
phenotype
observable characteristics
genotype
genetic make up
Monohybrid cross
matings between individuals that differ in one trait
Alelles
An alternative form of a single gene
Genes
Discrete units of alleles
Polymorphic
The existance of two or more variants in a population of individuals, with at least two of the variants having frequencies greater than 1%
Monomorphic
Genes that have only one allele that is normally present in a population
Law of Segregation
Two alleles for each trait are seperated during gamete formation. Then, unite at random, one from each parent at fertilization
SBE1
Enzyme responsible for starch branching. Creates wrinkled peas and smooth peas
Test Cross
Unknwon genotype crossed with homozygous recessive to determine the genotype of the unknown
Law of Product
The probability of two or more independent events occuring together is the product of the probabilities that each event will occur by itself.
Heterozygote Cross
phenotypic ratio of 3:1
The Law of Sum
The probability of either of two mutually exculsie events occuring is the sum of their individual probabilities
Dihybrid Cross
Two trait cross; phenotypic ratio of 9:3:3:1
Thomas Hunt Morgan
Experimented with Drosophila and discovered that the gene for eye colour is on the X chromosome. Also discovered chiasmata were recombination occurs.
Creighton and McClintock
Studied Corn
A.H Sturtevant
Proposed that % recombination or RF could be used as a gauge of the physical distance between any two genes on the same chromosome
Prokaryotic Promoter Regions
-35 region and -10 region
RNA Polymerase
Two alpha and 2 beta components. Sigma factor allows it to bind to promoter region
Monod and Jacob
1950s studied E.coli lactose utilization mutants
Polycistronic mRNA
One mRNA with 2 or more transcribed genes on it
Operon
A unit of DNA composed of specific genes, plus a promoter and operator that allows regulation if there are environmental changes
Constitutive mutants
Always result in protein sysnthesis, irrespective of environmental conditions
Corynebacterium diphtheriae
Toxin is repressed when the repressor and iron form together to create an inhibitor to block RNA polymerase
Diphtheria toxin
Stops the transfer of growing polypeptide chains from A site to P site of ribosomes. Ultmatley results in cell death.
Cap sequences
Eukaryotes only. Binding site for ribosome subunits to allow translation
Cis-factors in transcription
Enhancers and promoter close to initiation site
Trans-factors in transcription
Proteins roduced during transcription bind to enhance or block transcription
Core promoter
Close to the genes coding region. Includes iniitation site where transcription begins
TATA box
In eukaryotes that contain a sequence of thynines and adenines that is located at a -30 position
CAAT box
-75 to -100 base pairs. Type of cis promoter element
Enhancer
Regulatory site that can be located far away from the core promoter, or can be quite close
Basal factors
bind to the promoter to maintain a basal level of transcription.
TBP (TATA box Binding protein)
Essential to the initiation of transcriptioon from all class II genes with a TATA box
TAFs
TBP associated factors
Transcription activators
bind to enhance sequences and can increase transcription aboe the basal level
Activators
Proteins bind to genes at sites known as enhancers and speed up the rate of transcription
Repressors
Proteins bind to selected sites called silencers and slows transcription
Coactivators
"Adapter" molecules that intergrate signals from activators and perhaps repressors
Basal Transcription Factors
In respnse to injunctions from activators, these factors position RNA polymerase at the start of transcription
Homodimers
Multimeric proteins composed of identical subunits
Heterodimers
Multimeric proteins composed of nonidentical subunits
Steroids
Work at the level of coactivation of transcription factors (activators) by creating a reversable allosteric effect, causing a conformational change to bind to enhancer
Horomone Steriods Receptors
ex glucocorticoid receptor. Always a zinc-finger transcription factor
Competition
The repressor binds to the enhancer to block the binding of an activator
Quenching type 1
Repressor binds and blcks the DNA binding region of an activator. The binding domain is blocked and unable to bind to enhancer
Quenching type 2
Repressor binds and blocks theactivation domain of an actiator. But the activator is unable to bind to the enhancer
Chromatin
Eukaryotic DNA that is wrapped around histone proteins to form units of nucleosomes. This causes the genes to be turned off so that transcription is very low or non-existant in individual genes
Histone
Positively charged
DNA
Negatively charged
Methylated genes
tightly wrapped, not accessible. No transcription
Acetyl group genes
Histone tails reduce electrical attraction to DNA causing repulsion. It unwraps the DNA from the histone to expose the gene
Heterochromatin
Highly condensed DNA
Epigenome
Methylation attaches to DNA to turn off gene
Phenotype frequency
the proportion of individuals in a population that are of a particular phenotype
Allele frequency
The proportion of all copies of the gene in a population that are given allele type
Genotype frequency
The proportion of individuals in a population that are of a particular genotype
Hardy-Weinberg Law
Defines the relationships between genotype and allele frequencies within a generation and from one generation to the next
Hardy-Weinberg Equilibrium
Hypothetical populations that satisfy all five assumptions
Genetic drift
Unpredictable, chance fluxations in allele frequency that have no effect on survival
Genetic natural selection
interactions between genetically determined phenotypes and environmental conditions that cause differential reproduction of certain genotypes
Fitness
An individual's relative ability to survive and transmit its genes to the next generation. Two basic components: viability and reproductive success. Measured by number of offspring
Natural Selection
The process that progressiely eliminates individuals whose fitness is low and chooses individuals of high fitness to survive and become the parents of the next generation
Relative Fitness
Ranges from 0 to 1. Used to calculate the realitive fitness for a gien genotype
Heterozygous advantage
Sometimes heterozygots have a higher fitness than either homozygotes
Polymorphic gene
More than one wildtype allele can exist of a gene
Transition
Switch purine with another purine, or pyrimidine to another pyrimidine
Transversion
purine switches with pyrimidine. Can occur with oxidation
Inversion
break off and the 3 prime and 5 prime switch ends. Flipping. Half circle 180 degree rotation of a chromosomal region that can occur following two double stranded breaks
Reciprocal translocation
Part of the chromosome has been replaced with a region from ANOTHER chromosome and vice versa. Changing places
Luria and Delbruk
1943 Used E.coli and bacteriophage T1 to test hypothesis regarding the mechanisms responsible for the appearence of a new phenotype
Lamarck
Theory of evolutuon through aquired traits
Mutagens
Physical or chemical agrent that raises the frequency of mutations above the spontaneous rate
Depurination
A purine (A or G) is removed from the deoxyribose sugar by hydrolysis. A OH group remains on the backbone. Deamination with NO changes the amino group to a carboxyl group and changes the type of purine or pyrimidine
T dimers
Carbons from both thymines that are adjacent to one another + UV light to create a kink in DNA. This is a covalent bond that prevents replication by DNA polymerase
Xeroderma pigmentosium
Autosomal recessive trait that causes an inactivation in endonucleases. Excision repair is not able to occur
Proodreading
DNA polymerase I and III has a 3 prime to 5 prime exonuclease activity that can recognize and remove misparied bases during synthesis
Unequal crossing over
Results in a duplication and deletion
Gene Dosage
The number of times a given gene is present in the gene
Duplications
Increase the copy number of a particular chromosomal region (more than 2 protein products)
Tandem duplications
Lie adjacent to eachother, either in the same order or reverse order
Nontandem duplications
two or more copies of a region that are not adjacent to eachother and may lie farther apart on the choromosome or different chromosomes
Fragile X syndrome
Large number of duplications of a CGG repeat on the end of the X chromosome. As a result, does not wrap up properly causing polymerase to slip during translation
Paracentric Inversion
Exclude the centromere
Pericentric Inversion
Include the centromere. Acrocentric to metacentric
Translocation
Large scale choromosomal rearragnements in which part of one chromosome becomes attached to another chromosome or parts of two different chromosomes trade places
Reciprocal transloaction
Parts of two different chromosomes trade places
Robertsonian translocation
reciprocral translocations arising from breaks at or near the centromeres to two acrocentric chromosomes. Results in one large and one small chromosome. The small chromosome may be lost
Non-reciprocal translocation
unequal exchanges between chromosomes where part of one chromosome moves to a different chromosome
DNA probes
Short single straded DNA of known composition that are labelled with 32P or fluorescent dyes
Mullis
Created PCR by using artificial Xeroxing
PCR
Using oligonucleiotides to flank sequence of intrest. Taq polymerase extends DNA
Sanger dideoxy sequencing
based on lack of 3 prime group to terminate chain elongation. ddT bonds with A sequences to form various lengths of DNA fragments
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