Lecture 6: Measuring Population Genetics Flashcards
What Is population genetics Theory (2)
-Developed during evolutionary synthesis
- Allows quantitative predictions of evolutionary change at the population level
What is varriation (3)
-Variation is signified by differences
-These differences can be in physical appearance, reporduction, metabolism, behavior etc.
-These differences can be caused by genetics (genetic variaition) or enviroment (phenotypic variation)
Point Mutation (2)
-Change in a single nucleotide (point) of an codon (GTG -> GAG)
-Creates new alleles
Chromosomal inversion (2)
-Inverting the neculeotides of an codon (CCT -> TCC)
-Alleles inside inversion are transmitted together as a unit
Gene duplication (2)
-Duplicating a codon (GAG -> GAG GAG)
-Redundant genes may acquire new functions through accumulation of additional mutations
Genome duplication (2)
-massive gene duplication
-Can create new species
Issues with measuring genetic Variation (3)
-many species difficult to rear in captivity
- complex inheritance of many traits
- breeding experiments not often feasible
Genetic Markers (4)
- “molecular phenotypes”
- heritable & polymorphic
- reflect allelic (DNA) variation at a locus
- allow direct measurement of genetic
differences without breeding experiments
Allozyme
variant forms of an enzyme which differ structurally but not functionally from other allozymes coded for by different alleles at the same locus.
Synonomus vs non synonomus mutations
-Synonomus mutations (aka “silent mutations”) are mutations that have no effect on the resulting amino acid
-non-synonomus mutations result in amino acid changes, affecting physical properties of the organism
exon vs intron (2)
-Exons are the parts of DNA or RNA that code for proteins, while introns are the non-coding or “neutral” parts.
-Introns are the parts removed by RNA splcing
Tandem repeates (2)
-“neutral regions” containing repeats of the samev nucleotide sequence (e.g., TATATATATATA)….
- repeat number highly variable among individuals
Hardy-wienberg law (4)
- relates allele frequencies to genotypic frequencies in an “ideal”
population - works because transmission of alleles to gametes is predictable
due to Mendelian segregation - Starting point for population genetics
- Helps us to interpret the genetic variation that we have
measured
H-W Assumptions (6)
- no mutation
- random mating
- infinitely large population
- no migration
- no selection
- (diploid organism, sexual, non-overlapping generations)
H-W Formulas
p² + 2pq + q² = p + q = 1.0
where:
p= frequency of dom allele
q = frequency of rec allele
p² = Frequency of homo dom genotype
q² = Frequency of homo rec genotype
2pq = freq of hetero genotype
Commong HW p and q frequencies
with two hetero (Aa) parents:
-1/4 will be AA, 1/4 will be aa, and 1/2 will be Aa
HW with more than 2 alleles
p²+ 2pq + q² + 2qr + r² + 2pr = 1.0
Heterozygosity (3)
-is the proportion of heterozygotes in a population
-Hₑ is the expected heterozygosity of a population and:
=2pq OR 1 - (p² + q²)
= 1 - (p² + q² + r² + s² …..) for multiple alleles
-Hₒ is observed heterozygosity and is what we actually observe in the population
What is high genetic variation within
populations? (3)
– Many alleles at a locus
– Many variable loci
– Even allele frequency … many heterozygotes
Locus (2)
-Plural = Loci
-physical location of a gene on the chromosome
Additive allele (2)
-alleles that have additive effects on the phenotype, often contribute to
metric traits such as size or height,
- e.g., + allele results in larger seeds and - allele results in smaller seeds:
++ have largest seeds, +- have medium seeds, – have smallest seeds
Genotype frequency (2)
- proportion of a given genotype in a population
-number of individuals with genotype XY/
total number of individuals (= N)
Allele frequency (2)
-proportion of a given allele in a population
number of copies of allele X/
total number of alleles (= 2N in diploids)
