Question

Discuss his principles of inheritance by answering the following questions. Two plants are being crossed, each heterozygous for blue flower color (B), with white (b) as the recessive color. What is the possibility that the offspring will have white flowers? Express your answer as a ratio. If one parent is also heterozygous for smooth peas, does this mean that all of the offspring with blue flowers will also have smooth peas? Explain your answer without using a Punnett square. Suppose both parents are also heterozygous for smooth peas (S), with wrinkled peas (s) as the recessive trait. Use a Punnett square to predict the possibility that the offspring will be homozygous for both flower color and pea texture. Make sure to include a Punnett square and express your prediction as a ratio.

Answer 1

Answer:

Q1 - What is the possibility that the offspring will have white flowers? Express your answer as a ratio.

A: White flowers only appear if the offspring is homozygous for b because this phenotype is recessive, so they have to present bb phenotype. If both parents are heterozygous (Bb), each one gives one gene at a time per individual after crossing, so 1/4 would be BB, 2/4 would be Bb and 1/4 would be bb.

Q2 - If one parent is also heterozygous for smooth peas, does this mean that all of the offspring with blue flowers will also have smooth peas? Explain your answer without using a Punnett square.

A: No, it doesn't mean that all blue flowers will present smooth peas because those genes are expressed in different loci, so they segregate independently.  There might be some blue flowers with smooth peas, but that is not mandatory for all of them.

Q3 - Suppose both parents are also heterozygous for smooth peas (S), with wrinkled peas (s) as the recessive trait. Use a Punnett square to predict the possibility that the offspring will be homozygous for both flower color and pea texture. Make sure to include a Punnett square and express your prediction as a ratio.

A: Parental genotypes are BbSs x BbSs. Given that the genes segregate independently, we will have the Punnett diagram as follows:

        BS        /    Bs    /     bS   /   bs

BS    BBSS   / BBSs  / BbSS  / BbSs

Bs    BBSs   / BBss  / BbSs   / Bbss

bS    BbSS  / BbSs  / bbSS  / bbSs

bs     BbSs / Bbss  / bbSs  / bbss

Homozygous genotypes are the ones that both genes are the same when expressed, either BB,bb,SS or ss. The probability the offspring is homozygous for both flower color and pea texture is 4/16, or 1/4.