Chapter 13, Problem 3A

Summary Introduction

Introduction :

The given illustration shows a cross between a heterozygous white grapefruit (Ww) with a homozygous red grapefruit (ww). After the cross,a phenotype of 50% white grapefruit and 50% red grapefruit is obtained.

Answer to Problem 3A

Correct answer :

The correct answer is option (B) 1:1

Explanation of Solution

Explanation/justification for the correct answer :

Option (B). It is evident from the Punnett square that genotypically, half of the offspring are heterozygous white grapefruit (Ww) and half of the offspring are homozygous red grapefruit (ww) in the ratio 1:1. Thus, this is the correct answer.

The explanation for the incorrect answer :

Option (A) 1:2:1. This ratio can be obtained by a cross between two heterozygous white grapefruit (Ww). Thus, this is an incorrect option.

Option (C).All are homozygous recessive. If one parent is heterozygous white grapefruit (Ww), then all offspring cannot be homozygous recessive. Thus, this is an incorrect answer.

Option (D). All are heterozygous. If one of the crossing parent is recessive (ww), then all offspring cannot be heterozygous. Thus, this is an incorrect answer.