Chapter 13, Problem 4A

Summary Introduction

Introduction :

If an individual has the dominant phenotype, its genotype may be homozygous or heterozygous. This is not always known. It is not necessarily as both a homozygous dominant and heterozygous genotype can result in the same dominant phenotype. A test is done to know the genotype of the individual.

Answer to Problem 4A

Correct answer :

The correct answer is option (C) a test cross.

Explanation of Solution

Explanation/justification for the correct answer :

Option (C) a test cross. A testcross can be done to determine the organism's genotype. In a testcross, the individual with the unknown genotype is crossed with a homozygous recessive individual. 1f the parent’s genotype is homozygous dominant, all of the offspring will have the dominant phenotype, if it is heterozygous, the offspring will show a 1:1 phenotypic ratio. Thus, this is the correct answer.

The explanation for the incorrect answer :

Option (A) a homozygous cross. A homozygous cross cannot be used to determine the genotype of a parent with a dominant phenotype. Thus, this is an incorrect option.

Option (B) a heterozygous cross. A heterozygous cross cannot be used to determine the genotype of a parent with a dominant phenotype. Thus, this is an incorrect option.

Option (D) a parental cross. A parental cross gives all dominant phenotype. Thus, this is an incorrect answer.