Chapter 11, Problem 24A

Summary Introduction

Introduction :

Genes are the blueprint for the human body and every cell in the body has a copy of the blueprint present in the nucleus. Each human cell has 23 pairs or 46 chromosomes. A chromosome condition may change by an alteration in the number or genetic structure of chromosomes.

Answer to Problem 24A

Correct answer :

The correct answer is option (B),trisomy.

Explanation of Solution

Explanation/justification for the correct answer :

Option (B) is trisomy. It is a condition in which a person has three copies of one of the chromosomes instead of two. The affected person will have 47 chromosomes instead of 46. Thus, the correct answer is an option (B).

The explanation for the incorrect answer :

Option (A) monosomy. It is a condition in which a person has only one copy of one of the chromosomes instead of two. The affected person will have45 chromosomes instead of 46.Thus, this is an incorrect option.

Option (C) isCodominance. It is a form of inheritance where both the alleles of a gene are expressed in a heterozygote. As a result, the phenotype of the offspring is a combination of the phenotype of the parents.Thus, this is an incorrect answer.

Option (D) is dominant traits. A dominant trait is an inherited characteristic that appears in an offspring which is determined by the dominant allele. Thus, this is an incorrect answer.