Population Genetics and Changing Allele Frequencies

Vocabulary-style flashcards covering population genetics, microevolution, macroevolution, Hardy-Weinberg equilibrium, and the forces of evolutionary change based on Chapters 15–16 lecture notes.

Population genetics

The study of the genetics of populations and how allele frequencies vary with time.

Evolution

A biological process that occurs when allele frequencies change over generations.

Population

A group of members of the same species in the same area that can mate and produce fertile offspring.

Allele

One version of a gene.

Gene Pool

The collection of all alleles in all members of a population.

Allele Frequency

How common a specific allele is in a population, calculated as the number of a particular allele divided by the total number of alleles in the population.

Genotype Frequency

The frequency of each type of genotype in a population, such as homozygotes ($AA$, $aa$) and heterozygotes ($Aa$).

Phenotype Frequency

How common a specific trait is in a population, such as the percentage of people with cystic fibrosis.

Microevolution

Small genetic changes due to changing allele frequencies in a population over time.

Macroevolution

Large genetic changes that result in the formation of new species.

Hardy-Weinberg Equilibrium

A theoretical condition where allele frequencies remain constant from generation to generation, indicating the population is not evolving.

Hardy-Weinberg Allele Frequency Equation

$p + q = 1$, where $p$ is the frequency of one allele and $q$ is the frequency of a second allele.

Hardy-Weinberg Genotype Frequency Equation

$p^2 + 2pq + q^2 = 1$, representing the frequencies of all genotypes in the population.

$$p^2$$

The Hardy-Weinberg representation for the frequency of the homozygous dominant genotype ($AA$).

$$2pq$$

The Hardy-Weinberg representation for the frequency of the heterozygous genotype ($Aa$).

$$q^2$$

The Hardy-Weinberg representation for the frequency of the homozygous recessive genotype ($aa$).

DNA Profiling

A technique developed in the 1980s that identifies individuals using portions of the genome, such as short repeated segments and SNPs.

Single nucleotide polymorphisms (SNPs)

Single base differences between chromosomes.

Identical by Descent

DNA sequences that are passed down from a common ancestor.

Run of Homozygosity

A region where both chromosome copies have the same DNA sequence, indicating two individuals share a recent ancestor.

Population Substructure

Smaller genetic groups within a larger population.

Steel Syndrome

A rare inherited bone disease caused by a mutation in the $COL27A1$ collagen gene, which is more common among Puerto Rican populations in East Harlem.

Nonrandom Mating

A condition where individuals do not choose mates randomly, causing certain genotypes to reproduce more often than others.

Consanguinity

Mating between relatives, which increases homozygous genotypes and the frequency of recessive genetic disorders.

Endogamy

Marriage within the same community or population group.

Gene Flow

The movement of alleles between populations when individuals migrate and mate.

Admixture

The mixing of genes from different populations when people reproduce.

Clines

Gradients or gradual changes in allele frequencies across geographic areas or between neighboring populations.

Genetic Drift

Random changes in allele frequencies caused by chance or sampling errors, having the greatest effect in small populations.

Founder Effect

The genetic impact that occurs when a small group leaves a larger population to start a new population, resulting in a small sample of original alleles.

Population Bottleneck

An event where a large population is drastically reduced in size, and the survivors rebuild the population with limited genetic diversity.

Mutation

A change in DNA that creates new alleles and introduces new genetic variation.

Genetic Load

The collection of harmful recessive alleles present in a population.

Natural Selection

The differential survival and reproduction of individuals with particular phenotypes favored by the environment.

Positive Selection

A process where a beneficial trait becomes more common in a population, such as lactase persistence.

Negative Selection

A process where harmful traits decrease in frequency because they reduce reproductive success.

Artificial Selection

A process where humans choose specific traits to breed for in organisms like dog breeds and crops.

Vertical Transmission

The movement of a mutation from one bacterial generation to another through cell division.

Horizontal Transmission

The passage of groups of resistant genes between bacterial cells through transposons or plasmids.

Balanced Polymorphism

A condition where two or more forces act in different directions on alleles, maintaining a harmful allele because carriers (heterozygotes) have an advantage.

Eugenics

The control of reproduction to change genetic traits in a population for social goals.

Positive Eugenics

A type of eugenics that encourages reproduction among people considered superior.

Negative Eugenics

A type of eugenics that restricts reproduction among people considered inferior.