AP BIOLOGY

Detailed explanation-1: -The correct answer is: Option A: 75% hairy stems 25% hairless stems. This can be explained as: Hairy stem is a purebred dominant trait = HH.

Detailed explanation-2: -Tomato plants usually have hairy stems. Hairless stems are present in tomato plants that are homozygous recessive for this trait.

Detailed explanation-3: -The parent generation has homozygous dominant and homozygous recessive characters, AABB (130 cm) and aabb (100 cm) respectively. On cross-fertilization between these two parents, there will be mixing of the gametes to give rise to heterozygous offsprings in the F1 generation.

Detailed explanation-4: -A Punnett square can be used to predict genotypes (allele combinations) and phenotypes (observable traits) of offspring from genetic crosses. A test cross can be used to determine whether an organism with a dominant phenotype is homozygous or heterozygous.

Detailed explanation-5: -An organism with one dominant allele and one recessive allele is said to have a heterozygous genotype. In our example, this genotype is written Bb. Finally, the genotype of an organism with two recessive alleles is called homozygous recessive. In the eye color example, this genotype is written bb.