Textbook Problem

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Assuming complete dominance, a cross between dihybrid F₁ pea plants produces F₂ phenotype ratios of ________.

1. a. 1:2:1
2. b. 3:1
3. c. 1:1:1:1
4. d. 9:3:3:1

Summary Introduction

Concept introduction: The allele is the variant of the gene. The allele can be dominant or recessive. The dominant allele is the one that will be expressed in the heterozygous condition where two different alleles of the same gene are present.  Phenotypic ratio refers to the ratio of the number of organisms in the generation that would express several phenotypes.

Explanation of Solution

Reasons for the correct statement:

The parents are homozygous dominant PPTT (purple flower (PP) and long- stemmed (TT)) and homozygous recessive pptt (white flower (pp) and short- stemmed (tt)). The F₁ generation will be PpTt.  The F₁ generation is self- crossed to give the F₂ generation. The F₂ generation will give the phenotypic ratio 9:3:3:1.

Option d. is given as “9:3:3:1”

As 9 purple flower tall stem, 3 purple flower short stem, 3 white flower long stem, and 1 white flower short stem give the phenotypic ratio 9:3:3:1 for dihybrid cross, option d...