Chapter 12, Problem 7STP

Summary Introduction

Introduction :

Human blood group is determined by a gene I. It has three alleles I^A and I^B and i. I is a dominant gene i is recessive gene. The genotype can be I^AI^A , I^Ai, I^BI^B, I^Bi, I^A I^B and ii which determines four types of blood groups A, B, AB and O.

If a person having alleles I^A and I^B, both genes are express completely resulting into a new phenotype. This reflects the alleles I^A and I^B are codominant.

Answer to Problem 7STP

Correct answer :

The correct answer is option (C).

Explanation of Solution

Explanation/justification for the correct answer :

Option (C). If a person having alleles I^A and i. This is the heterozygous condition, the blood group will be A. Thus, this is the correct answer.

The explanation for the incorrect answer :

Option (A) I^BI^B. If a person having allelesI^BI^B.This is the homozygous condition, the blood group will be B. Thus, this is an incorrect option.

Option (B) ii. If a person having alleles ii. This is the homozygous recessive, the blood group will be O. Thus, this is an incorrect option.

Option (D) I^AI^B. This is condition in which both alleles are codominant, the blood group will be AB. Thus, this is an incorrect answer.