Evolution and Population Genetics

Vocabulary-style flashcards covering the principles of population genetics, evolutionary change, Hardy-Weinberg equilibrium, and types of selection based on lecture notes.

Evolution

Changes in allele frequency over time.

Gene

The basic unit of heredity; a sequence of DNA nucleotides that codes for a specific information.

Nucleotide

The building block for nucleic acids.

Purines

A category of nitrogen-containing bases that includes Adenine and Guanine.

Pyrimidines

A category of nitrogen-containing bases that includes Thymine, Cytosine, and Uracil.

Genome

The entire DNA sequence of an organism.

Phenotype

The expression of genetic information.

Diploid ($2n$)

An organism or cell having two complete sets of chromosomes, such as humans who have 46 chromosomes in 23 homologous pairs.

Haploid ($n$)

A cell containing a single set of chromosomes, such as gametes (egg and sperm).

Locus

The specific location of a gene on a chromosome.

Alleles

Variations of the same gene.

Hardy-Weinberg Principle

A principle that allows for the prediction of allele frequencies within a given population, assuming no mutations, no migration, random mating, large population size, and no selection.

Hardy-Weinberg Equation

$p+q=1$ (for allele frequency) and $p^2 + 2pq + q^2 = 1$ (for genotype frequency).

Gene flow

An agent of evolutionary change that occurs when alleles move between populations.

Assortative mating

A type of nonrandom mating that increases the frequency of homozygotes.

Disassortative mating

A type of nonrandom mating that increases the frequency of heterozygotes.

Founder Effect

A form of genetic drift exemplified by the Amish community in Lancaster County, where the recessive trait for Ellis-van Creveld syndrome is common due to descendants of a single founding couple.

Bottleneck Effect

A form of genetic drift caused by a drastic reduction in population size, potentially leading to recovery or extinction.

Fitness

A measure of reproductive success resulting from differences in survival, mating success, and the number of offspring per mating event.

Parental investment

The energy expended on reproduction.

Intrasexual selection

Competition for mates between members of the same sex.

Intersexual selection

Mate choice between members of opposite sexes.

Negative frequency-dependent selection

A process where rare phenotypes have higher fitness.

Positive frequency-dependent selection

A process where rare phenotypes have lower fitness.

Oscillating Selection

Selection that favors one phenotype at one time and another phenotype at another time, such as beak depths in the Medium ground finch of the Galápagos Islands during wet or dry years.

Heterozygote advantage

A situation where heterozygotes are favored over homozygotes, such as individuals with the sickle cell allele ($Aa$) being resistant to malaria with only mild disease symptoms.

Disruptive Selection

Selection that acts against intermediate phenotypes and favors both extremes, leading to two distinct peaks in the population distribution.

Directional Selection

Selection that favors individuals at one end of the phenotypic range, causing the peak of the distribution to shift.

Stabilizing Selection

Selection that favors intermediate or mid-size individuals and acts against extreme phenotypes, making the distribution narrower.

Epistasis

The interaction between two or more genes to control a single phenotype.

Pleiotropy

A condition where one single allele affects many different and often unrelated aspects of a phenotype.