Principles of Inheritance and Variation

Answer

During gamete formation, the two alleles of a gene separate (segregate) from each other so that each gamete carries only one allele. Also called the Law of Purity of Gametes.

Answer

Alleles of different genes assort independently of each other during gamete formation, provided they are on different (non-homologous) chromosomes. Gives 9:3:3:1 ratio in dihybrid cross.

Answer

Reasons: (1) Short life cycle, (2) Large number of offspring, (3) Clear contrasting traits, (4) Bisexual flowers — easy self or cross pollination, (5) Pure breeding varieties available, (6) Inexpensiv…

Answer

3:1 phenotypic ratio in F2 generation of a monohybrid cross. 3 dominant : 1 recessive. Genotypic ratio is 1 AA : 2 Aa : 1 aa.

Answer

9:3:3:1 phenotypic ratio in F2 of a dihybrid cross. 9 dominant-dominant : 3 dominant-recessive : 3 recessive-dominant : 1 recessive-recessive.

Answer

Cross between an organism of unknown genotype (dominant phenotype) with a homozygous recessive (aa). If offspring ratio is 1:1, parent is Aa (heterozygous). If all dominant, parent is AA (homozygous).

Answer

Neither allele is completely dominant. F1 hybrid shows an intermediate phenotype. Example: Snapdragon flower (Antirrhinum majus) — RR × WW → all pink (RW) in F1; F2 = 1 RR (red) : 2 RW (pink) : 1 WW (…

Answer

Both alleles are expressed simultaneously in the heterozygote. Example: ABO blood group — IA and IB are codominant. Type AB individuals express both A and B antigens on red blood cells.