Lecture 12: Population Genetics and Exercise 10 Genes in Populations

Population

These are a group of individuals of the same species that live in the same area, (potentially) interbreed, produce fertile offspring, and share the same gene pool

Population genetics

study of heredity and variation in a population

Gene pool

All copies of every type of allele at every locus in all members of the population

Genotype frequencies

The relative proportion of a specific genotype for a gene to all genotypes for that gene in the population

What is the formula for Genotype frequencies?

The relative proportion of an allele of a gene to all alleles of that gene in the population

What is the formula for:

Solve for f(A) and f(a)

This principle states that the frequencies of alleles and genotypes in a population will remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work.

What are the Conditions for Hardy-Weinberg Eq.?

Look for genotype and gene frequencies.

Population Genetics

It is concerned with heredity in groups of individuals or population and how the genetic constitution changes from generation to generation

Population Genetics

It studies the genetic constitution of population and predicts the fate of a gene in a population

What determines an Effective population size?

Gene frequency

It is the relative proportion of the different alleles of a gene in a population

Gene pool

It is the sum total of genes in the reproductive gametes of the population

It is also know as the gametic pool

Gene pool

Here Samples are drawn at random and we must include the gametes that will form the zygote for the next generation

Godfrey H. Hardy (Mathematician)
Wilhelm Weinberg (Physician)

In 1908 they independently derived the equations for Hardy-Weinberg equilibrium

What are the Consequences of H-W equilibrium

Given:
Solve for genotypic frequencies of EE, Ee, and ee

Compute for the frequency of carriers.

What are the Factors that could change gene frequencies?

Mutation

Factor that could change gene frequencies in which:

Migration

Factor that could change gene frequencies in which:

addition or removal of alleles in a population

Selection

Factor that could change gene frequencies in which:

considers reproductive advantage or disadvantage of a particular genotype

Random genetic drift

Factor that could change gene frequencies in which:

change in allele frequency is due to sampling error

What is the formula for a one way recurrent mutation after n^th generation?

What is the formula for bi-directional mutation after n^th generation?

What is the formula for p and q at equilibrium after bi-directional mutation?

Solve for q and p.

Selection

When Genotypes differ in their capacity for survival and reproduction.

Selection

- guiding force in evolution
- real test of mutation

Mutation; selection

_________ proposes while __________ disposes

relative fitness

It is the reproductive success of one phenotype as opposed to alternative phenotype

Selection pressure

It is the force acting upon a phenotype to reduce its fitness or adaptive value

Selection coefficient formula

Given:
Solve for the Gene frequencies after selection

What are the Modes of Selection?

Stabilizing

Modes of Selection

phenotypic extremes are eliminated

Stabilizing

Modes of Selection

The phenotypes close to the mean are preserved by the populations that are environmentally well adapted.

Directional

Modes of Selection

one extreme is favored

Disruptive or diversifying

Modes of Selection

both extremes are selected for

Migration
What are the Important factors to the recipient population?

m = proportion of the migrants to the mixed population, so

(migrants)/(migrants + recipient)

What is the migration formula?

Find q₁ and p₁.

m = (25)/(25+75)

Random genetic drift

It is the random change in allelic frequency due to sampling error

Random genetic drift

Its change is in random direction and is dependent on population size

Random genetic drift

- causes homozygosity
- loss of genetic diversity

significant
negligible

- for small population, Random genetic drift is ___________
- for large population, Random genetic drift is ___________

If a small number of individuals migrate into a new location, they become founder of a new population.
- founder effect
- proposed by Mayr (1952)

If a small number of individuals migrate into a new location, they become __________ of a new population.
- _____________
- proposed by _______ (1952)

FOUNDER EFFECT

FOUNDER EFFECT

Inbreeding

mating between individuals with common ancestry

Consequences of inbreeding

1. genetic uniformity

2. reduced vigor

3. reduced viability

4. reduced fertility

What are the Consequences of inbreeding?

1. genetic _________

2. reduced _________

3. reduced _________

4. reduced _________

inbreeding depression

It is the appearance of deleterious phenotypes

inbreeding coefficient (F)

It is the probability that any two alleles at a locus are alike by descent

Divergence within a population occurs due to the ff:

Race

These are genetically distinct populations of the same species that differ in the relative frequency of some genes

Race is a consequence of:

False

Race is an irreversible process.

T or F

It is a group of interbreeding natural population that is reproductively isolated and share a common gene pool

Speciation can occur if there is:

Allopatric speciation

These are species that inhabit separate geographic reg

Sympatric speciation

These are species that inhabit at least in part the same ge