Week 9 - Genetic Evidence of Divergence

Vocabulary flashcards covering key concepts from Week 9 lecture notes on genetic divergence, allele frequencies, SNPs, heritability, epigenetics, and obesity genetics.

Allele frequency

The percentage of gene copies of a particular allele in a population; changes in allele frequency indicate evolution.

Population genetics

The study of how evolutionary change affects allele frequencies in populations.

SNP (Single Nucleotide Polymorphism)

A single base pair difference among individuals used to analyze alleles; 99% of the genome is identical; the remaining 1% differences are largely SNPs.

Unique alleles

Isolation over generations can lead to some alleles that are unique to a population.

1% genome variation

The portion of the human genome that differs among individuals, largely consisting of SNPs.

No SNP in all members

No SNP is found in every individual of any population; some populations may have no individuals with a given SNP.

Sickle-cell allele

An allele that causes sickle-cell anemia when homozygous; in heterozygotes, may confer malaria protection in certain regions.

Carrier rate

The proportion of individuals carrying one copy of the sickle-cell allele (heterozygotes).

Sickle-cell geography

Presence of the sickle-cell allele is higher in malaria-endemic regions and relates to geography rather than race.

Human Genome Project

A large project providing data to examine allele patterns and variation across populations.

Not universal to race

Most SNPs have no known effect on phenotype, and no SNP is present in all individuals of any race.

Natural selection in humans

Evolutionary change in allele frequencies due to environmental pressures (e.g., malaria influencing sickle-cell allele frequencies).

Sickle-cell adaptation

Carrying one copy of the sickle-cell allele increases fitness in malaria regions by reducing parasite reproduction.

Convergent evolution

Unrelated organisms independently evolve similar traits due to similar environments.

Skin color and UV exposure

Strong correlation between skin color and UV exposure; adaptation balances folate protection and vitamin D synthesis.

Folate and vitamin D trade-off

Darker skin protects folate in high UV; lighter skin aids vitamin D synthesis in low UV.

Polygenic traits

Traits influenced by many genes and environmental factors; show continuous variation.

Eye color genetics

Eye color is determined by 2 to 15 genes and melanin distribution; contributes to phenotypic variation.

Skin color genetics

Skin color is determined by at least three genes and is influenced by melanin and environment.

Quantitative traits

Traits involving many genes and environmental factors; show continuous variation and are often normally distributed.

Normal distribution

Bell-shaped curve; mean is the average; variance measures the spread of trait values.

Heritability

The proportion of variation in a trait within a population explained by genetic differences.

Natural experiments

Studies where one factor (genes or environment) is naturally removed to separate genetic from environmental effects.

Monozygotic twins

Identical twins; develop from one zygote; about 1 in 285 pregnancies.

Dizygotic twins

Fraternal twins; develop from two eggs and two sperm; about 1 in 80 pregnancies.

Twin studies

Compare trait similarity between monozygotic and dizygotic twins to separate genetic from environmental effects (e.g., criminality correlation ~0.55).

Epigenetics

Study of how gene expression changes due to environmental influence without changing the DNA sequence; environment shapes expression and epigenetic markers can be inherited.

Phenotype

Observable traits of an organism; influenced by gene expression and environment.

Agouti epigenetics

Agouti mice example: a diet adding methyl groups to DNA altered gene expression; offspring were lean and brown; epigenetic marks can be inherited.

Maze-related heritability

Some highly heritable traits (e.g., maze-running ability) can still respond to environmental enrichment and experience.

BMI

Body Mass Index (BMI) = weight (kg) ÷ height² (m²); obesity is a multifactorial trait.

Obesity factors

Affected by genetic and environmental factors such as muscle mass, physical activity, diet, metabolism, and psychology.

Types of obesity

Syndromic (few genes, large effects), Monogenic (single gene with large effect), Common obesity (polygenic with many genes and small effects) in combination with environment.

PKU (Phenylketonuria)

Defect in phenylalanine hydroxylase (PAH) causing buildup of phenylalanine; environment (diet) can modify outcomes; treatable with diet.

Gene-environment interaction

Genes influence susceptibility and the environment determines expression; outcome depends on their interaction.