- Point Mutations: single-base substitutions (silent, missense, nonsense)
- Frameshift Mutations: insertions/deletions altering reading frame
- Chromosomal Mutations: deletions, duplications, inversions, translocations
Chapter Summary
Genetic variation arises from mutation, recombination, and random mating. Mutation types include point, frameshift, and chromosomal. Population genetics models (Hardy–Weinberg) predict allele frequencies under ideal conditions.
Mutation Types
Nondisjunction
Failure of chromosome pairs to separate during meiosis I or II → gametes with abnormal chromosome numbers (aneuploidy). Example: Trisomy 21 (Down syndrome) results from nondisjunction of chromosome 21.
Sources of Genetic Diversity
- Crossing Over: exchange of segments between homologous chromosomes in Prophase I
- Independent Assortment: random alignment of homologs at Metaphase I
- Random Fertilization: random union of gametes
Key Terms
- Aneuploidy: abnormal chromosome number
- Frameshift: mutation shifting reading frame
- Alelle Frequency: proportion of allele in population
- p², 2pq, q²: genotype frequencies under Hardy–Weinberg
Quiz Yourself
1. A deletion of one base causes:
2. Trisomy 21 results from:
3. In Hardy–Weinberg, q = 1 − p. If p = 0.7, q = ___.