Chapter 10, Problem 14A

Summary Introduction

Introduction:

A cross that involves hybrids for a single trait is called a monohybrid cross. Punnett developed a method to predict the possible offspring of a cross between two known genotypes. It is easier to keep a track of the possible genotypes involved in a cross.

Answer to Problem 14A

Correct answer :

The correct answer is option C. 1:1 black to white

Explanation of Solution

Explanation/justification for the correct answer:

Option C. 1:1 black to white−A Bb guinea pig will produce two types of gametes- male and female- each with either the B allele or b allele. A bb guinea pig will produce two types of gametes- male and female- both with b allele. If a black guinea pig ( Bb ) crossed with a white guinea pig ( bb ), there are only two possible genotypes; Bb and bb. So the resulting phenotypic ratio will be 1: 1 black to white as equal number of black and white guinea pigs will be produced.

This can be checked by drawing a Punnett square as shown below.

	B	b
b	Bb	bb
b	Bb	bb

Hence this is the correct option.

Explanation for incorrect answer:

Option A. 0:1 black to white- If a black guinea pig ( Bb ) crossed with a white guinea pig ( bb ), there are only two possible genotypes; Bb and bb. So the resulting phenotypic ratio will be 1: 1 black to white as equal number of black and white guinea pigs will be produced. Two black guinea pigs will be produced. Hence this is not the correct option.

Option B. 1:0 black to white- If a black guinea pig ( Bb ) crossed with a white guinea pig ( bb ), there are only two possible genotypes; Bb and bb. So the resulting phenotypic ratio will be 1: 1 black to white as equal number of black and white guinea pigs will be produced.Two white guinea pigs will be produced.Hence this is not the correct option.

Option D. 3:1 black to white-If a black guinea pig ( Bb ) crossed with a white guinea pig ( bb ), there are only two possible genotypes; Bb and bb. So the resulting phenotypic ratio will be 1: 1 black to white as equal number of black and white guinea pigs will be produced.Three black guinea pigs will not be produced.Hence this is not the correct option.