Chapter 10, Problem 17A

Summary Introduction

To explain:

Occurrence in F₃ generation of the curly-eared cat.

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. Some traits are dominant while some are recessive.

Answer to Problem 17A

The curly- eared cat is produced in the F₃ generation as well.

Explanation of Solution

In F₂ generation three genotypes were produced; CC, Cc, cc in the ratio of 1:2:1. Now if they reproduce with cats that have non-curled ears; a F3 generation will have following combinations:

   1. A CC catwith Cc − This cross will produce cats with all non-curled ears.

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

	C	C
C	CC	CC
c	Cc	Cc

   2. A Cccat with Cc − This cross will produce cats in the ratio of 3:1 non-curled ears to curled ears.

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

	C	c
C	CC	Cc
c	Cc	cc

  3. A cc cat with Cc − This cross will produce cats in the ratio of 1:1 non-curled ears to curled ears.

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

	c	c
C	Cc	Cc
c	cc	cc

Hence it can be concluded that the trait for curled ears was masked in some cats in F₂ generation. This becomes clearly visible in F₃ generation.