Module 1-4

What process in meiosis increases variation by shuffling chromosomes during metaphase I?

Independent assortment

What happens during crossing over in meiosis?

Homologous chromosomes exchange segments to increase genetic variation

What is the result of mitosis?

Two identical diploid daughter cells (2n)

What is the result of meiosis?

Four unique haploid gametes (n)

What separates during meiosis I?

Homologous chromosomes

What separates during meiosis II?

Sister chromatids

What's the genotype ratio of a Aa x Aa cross?

1 AA : 2 Aa : 1 aa

What's the phenotype ratio of a Aa x Aa cross (with complete dominance)?

3 dominant : 1 recessive

What does the Law of Segregation state?

Alleles separate during gamete formation

What does the Law of Independent Assortment state?

Alleles of different genes separate independently

What is incomplete dominance?

Heterozygotes show a blended trait (e.g. red + white = pink)

What is codominance?

Both alleles are fully expressed (e.g. AB blood type)

What is pleiotropy?

One gene affects multiple traits

What is polygenic inheritance?

Multiple genes influence a single trait (e.g. skin color)

What is a test cross?

Cross unknown genotype with homozygous recessive to determine genotype

Why are X-linked traits more common in males?

Males only need one copy of the recessive allele (XY)

What is the Hardy-Weinberg equation?

p² + 2pq + q² = 1 and p + q = 1

What are the 5 assumptions of Hardy-Weinberg equilibrium?

No mutations, random mating, no natural selection, large population size, no gene flow

What is genetic drift?

Random change in allele frequencies, especially in small populations

What is the bottleneck effect?

A sudden population reduction that randomly changes allele frequencies

What is the founder effect?

Small group starts new population with different allele frequencies

What is gene flow?

Migration of individuals into or out of a population, changing allele frequencies

What is natural selection?

Traits that increase fitness become more common over time

What does fitness mean in evolution?

An individual's ability to survive and reproduce

What is directional selection?

Favors one extreme phenotype

What is stabilizing selection?

Favors the average trait; reduces extremes

What is disruptive selection?

Favors both extremes over the average

What is a prezygotic barrier?

A reproductive barrier that prevents fertilization (e.g. behavioral, temporal, mechanical)

What is a postzygotic barrier?

A barrier that occurs after fertilization (e.g. hybrid sterility or inviability)

What is speciation?

The formation of a new species