Chapter 11, Problem 6STP

Summary Introduction

Introduction:

Scientists study family history using a diagram that traces inheritance of a particular trait through several generations. Such diagrams are called pedigree. A pedigree uses symbols to illustrate the inheritance of trait. By analyzing the pedigree we can predict if the person will suffer from disease or will be a carrier of the disease or will be disease free.

Answer to Problem 6STP

Correct answer :

The correct answer is option B. II1

Explanation of Solution

Explanation/justification for the correct answer:

Option B. II1- The given pedigree illustrates inheritance of a genetic disorder. In this diagram, I1 and I2 are parents who carry the genes for a disease/ disorder. Males are represented by squares and females are represented by circles. One who expresses the trait is represented by a dark, or filled square or circle. In this pedigree, II1 is dark. So it expresses the trait and would develop symptoms of the disease.

Hence this is the correct option.

Explanation for incorrect answer:

Option A. I1- In a pedigree diagram, an unfilled square or circle does not express the trait. A partially filled square or circle does not express the trait but is a carrier of the trait. II1 is a carrier of the disease. So it will not develop the symptoms of the disease.

Hence this is not the correct option.

Option C. II3- A partially filled square or circle does not express the trait but is a carrier of the trait. II3 is a carrier of the disease. So it will not develop the symptoms of the disease.

Hence this is not the correct option.

Option D. III1- A partially filled square or circle does not express the trait but is a carrier of the trait. III1 is a carrier of the disease. So it will not develop the symptoms of the disease.

Hence this is not the correct option.