Question

question 20 2.5 points a genetic cross of pure breed red - flowered snapdragons with pure breed white - flowered snapdragons resulted in f1 - hybrid offspring that all had pink flowers. when the f1 plants were self - pollinated, the resulting f2 - generation plants had a phenotypic ratio of 1 red: 2 pink: 1 white. what is the most likely explanation? a incomplete dominance b incomplete penetrance c codominance d phenocopy question 21 2.5 points the ability to roll your tongue into a u - shape is a recessively inherited trait. what is the possible parental combination that would produce a child with this trait? a rr×rr b rr×rr c rr×rr d rr×rr e both rr x rr and rr x rr

Explanation:

For Question 20, incomplete dominance occurs when the heterozygous phenotype is an intermediate between the two homozygous phenotypes. In the snap - dragon cross, the pink flowers in F1 are an intermediate between red and white, and the F2 ratio of 1 red: 2 pink: 1 white is characteristic of incomplete dominance. For Question 21, a recessive trait is expressed when an individual has two copies of the recessive allele. Parental combinations of Rr x Rr can produce offspring with the recessive trait (rr) through Mendelian inheritance, and rr x rr parents will always produce offspring with the recessive trait.

Answer:

Question 20: A. Incomplete dominance
Question 21: E. both Rr X Rr and rr X rr