POPULATION GENETICS

Genetic Population

The sum of gene (or allelic) frequencies for all the genes represented by that population

Allele Frequency/Gene Frequency

The proportion of a particular allele (variant of a gene) among all allele copies being considered

Gene Pool

Set of all genes or genetic information in any population usually of a particular species 

Fitness 

The ability to both survive and reproduce

Linkage Equilibrium

Populations where combinations of alleles or genotypes can be found in the expected proportions 

Linkage Disequilibrium

Non-random association of alleles at two or more loci, that descend from single, ancestral chromosomes 

Population Genetics

Is the study of the distributions and changes of allele frequency in a population, as the population is subject to the five main evolutionary processes. This also takes into account the factors of recombination, population subdivision, and population structure

Natural Selection, Genetic Drift, Mutation, Gene Flow, Non-random Mating

What are the 5 main evolutionary processes:

p2 + 2pq + q2

Formula of the Hardy-Weinberg-Principle

p2

In the Hardy-Weinberg-Principle, this is the symbol for the frequency of homozygous dominant genotype

2pq

In the Hardy-Weinberg-Principle, this is the symbol for the frequency of heterozygous genotype

q2

In the Hardy-Weinberg-Principle, this is the symbol for the frequency of homozygous recessive genotype

Hardy-Weinberg equilibrium, model, theorem, law

Hardy-Weinberg principle is also known as?

Hardy-Weinberg Principle

This predicts how gene frequencies will be inherited from generation to generation given a specific set of assumptions

Large Population Size, No migration, No net mutations, Random mating, No natural selection

What are the assumptions of Hardy-Weinberg Principle?

Large Population 

This is one of the assumptions on the H-W principle that states: small populations have fluctuations in allele frequencies (e.g., fire, storm)

No migration

This is one of the assumptions on the H-W principle that states:
Immigrants can change the frequency of an allele by bringing in new alleles to a population

No net mutations

This is one of the assumptions on the H-W principle that states:

If alleles change from one to another, this will change the frequency of those alleles

Random mating

This is one of the assumptions on the H-W principle that states:
If certain traits are more desirable, then individuals with those traits will be selected and this will not allow for random mixing of alleles

No natural selection

This is one of the assumptions on the H-W principle that states:
If some individuals survive and reproduce at a higher rate than others, then their offspring will carry those genes and the frequency will change for the next generation

Unchanged, constant

If the only force acting on the population is random mating, allele frequencies remain ________ and genotypic frequencies are ______

Mendelian genetics 

This implies that genetic variability can persist indefinitely, unless other evolutionary forces act to remove it

Natural selection, genetic Drift, Mutation, Gene Flow, Non-random mating

Five forces of evolution:

Natural Selection

This force of evolution states that some traits make it more likely for an organism to survive and reproduce 

Fitness

This is a propensity or probability of survival and reproduction in a particular environment

Directional, Disruptive, Stabilizing selection

What are the modes of selection:

Directional Selection

This mode of natural selection favors individuals at one end of the phenotypic range, most common during times of environmental change or when moving to new habitats 

Disruptive Selection

This mode of natural selection favors extreme over intermediate phenotypes, occurs when environmental change favors an extreme phenotype

Stabilizing Selection

This mode of natural selection favors intermediate over extreme phenotypes, reduces variation and maintains the current average

Genetic drift

This force of evolution states that a change in allele frequencies caused by random sampling, may cause gene variants to disappear completely, and thereby reduce genetic variability.

Larger

What is the effect of genetic drift on smaller populations?

Smaller

What is the effect of genetic drift on larger populations

Bottleneck, Founder Effect

What are the population events in genetic drift?

Bottleneck Effect

This population event in genetic drift states that the population is vastly reduced in numbers (e.g. a hurricane kills most individuals in the population)

Cheetas

These species have little genetic variation in their gene pool

Founder Effect 

This population event in genetics states that few individuals leave the original population and found a new population (e.g. colonize an island). As with bottlenecks, they are likely not representative of the original population

Mutation

This is the ultimate source of genetic variation in the form of new alleles, can result in several different types of change in DNA sequences; these can either have no effect, alter the product of a gene, or prevent the gene from functioning. 

Gene Flow

This occurs when alleles are exchanged between two populations, occurs when individuals migrate (immigrate or emigrate) and breed in a new population (contributing their genes to that population). Increases the variability of the gene pool by adding new alleles.

Hybridization

Gene flow can also occur through?

Non-Random mating

Occurs when individuals have mating preferences rather than randomly mating with any other individual in the population

Assortative Mating, Inbreeding, Sexual selection

Several ways non-random mating may occur:

Assortative Mating

This a non-random mating where individuals with similar genotypes and/or phenotypes mate with one another more frequently than what would be expected under a random mating pattern.

Negative assortative mating

Individuals with diverse traits mate more frequently than what would be expected in random mating

Inbreeding

This a non-random mating where the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically.

Outcrossing

This refers to mating with unrelated individuals

Sexual Selection

This a non-random mating where some individuals out-reproduce others of a population because they are better at securing mates

Complications 

Basic models of population genetics consider only one gene locus at a time. In practice, epistatic and linkage relationships between loci may also be important 

Epistasis

Gene at one locus affects phenotypic expression of another gene of a second locus

Linkage

The tendency of genes or other DNA sequences at a specific loci to be inherited together as a consequence of their physical proximity on a single chromosome

Separated, chromatids

Genes that loci are nearer to each other are less likely to be ______ onto different _______ during chromosomal crossover, and are therefore said to be genetically linked

Lower, Inherited

The nearer two genes are on a chromosome, the _____ is the chance of a swap occurring between them, and the more likely they are to be _____ together