Mendel's Principles

What was the pre-Mendel concept of inheritance?

Blending inheritance: offspring inherit the average of parent traits, which would reduce variation.

What did Mendel propose instead of blending inheritance?

Particulate inheritance: traits are passed as discrete units (alleles), preserving variation.

What is a genotype?

The genetic makeup of an organism (allele combinations).

What is a phenotype?

The observable trait or characteristic.

What is dominance?

When one allele masks the expression of another in heterozygotes.

Why is dominance not blending?

Because recessive traits can reappear in later generations.

What are Mendel's two laws?

1) Law of Segregation: gametes carry one allele per locus. 2) Law of Independent Assortment: alleles of different loci assort independently if on different chromosomes or far apart.

What causes independent assortment?

Alleles are on different chromosomes or far enough apart for recombination.

What does recombination do?

Generates new combinations of alleles in gametes not found in the parents.

What is a population?

Group of interbreeding individuals of the same species in the same place/time.

What is a gene pool?

All alleles for all genes in a population.

What is population genetics?

Study of forces that influence allele frequencies in populations.

What are the 5 evolutionary forces?

Nonrandom mating, mutation/recombination, selection, gene flow, genetic drift.

What processes do the mechanisms of evoulution effect?

1) Production of gametes, 2) Unification of gametes, 3) Production of phenotypes.

What is the Hardy-Weinberg Model?

"Model of no evolution"; allele and genotype frequencies remain constant if assumptions are met.

What is the Hardy-Weinberg equation?

p² + 2pq + q² = 1.

What does p² represent?

Frequency of homozygotes for allele 1.

What does 2pq represent?

Frequency of heterozygotes.

What does q² represent?

Frequency of homozygotes for allele 2.

What are the Hardy-Weinberg assumptions?

Random mating, no mutation, no migration, no natural selection, infinite population size.

What does it mean if a population is in Hardy-Weinberg equilibrium?

Genotype frequencies follow p² + 2pq + q² and allele frequencies don't change.

What is positive assortative mating?

Mating with similar phenotypes → increases homozygotes.

What is negative assortative mating?

Mating with dissimilar phenotypes → increases heterozygotes, maintains diversity.

What is inbreeding?

Mating with relatives → increases homozygotes but doesn't change allele frequencies.

Are insect and bird wings homologous?

No, they are convergent structures (analogous), not inherited from a common ancestor.

What are lines of evidence for evolutionary history?

Fossil record, comparative anatomy, embryology, biochemistry, genetics, biogeography.

What is uniformitarianism?

The idea that natural processes are gradual and consistent over time (the present reflects the past).