Chapter 8.3, Problem 34AQP

a.

Summary Introduction

To explain: Different types of gametes produced by man who is a carrier of Robertsonian translocation between chromosome $13$and$22$.

Introduction: Chromosomal analysis or chromosomal karyotype is used to find the chromosomal abnormalities. It is used to diagnose genetic diseases and birth defects. Disorders due to chromosomal abnormalities such as Down syndrome, Turner syndrome, and Edwards syndrome can be diagnosed using chromosomal karyotyping.

Explanation of Solution

In case, if the segregation of translocated chromosome takes place from chromosome $13$and $22$ then gametes will either have one normal chromosome $13$and one normal chromosome$22$ or two translocated copies.

In case, if the segregation of chromosome $22$take place from chromosome$13$, then gametes formed will have three translocated chromosomes $13$and $22$, chromosome$22$, or $4$normal chromosome$13$.

In case, if the segregation of chromosome $13$takes place from chromosome $22$, then gametes will have either $5$translocated copies of chromosome $13$and $22$ and $5$normal chromosome $13$or $6$normal chromosome $22$.

b.

Summary Introduction

To explain:

Type of zygote that will develop from fusion of each type of male gamete with female gametes.

Explanation of Solution

Female have normal chromosome $13$and $22$and male have Robertsonian translocation. So there are possibly six different types of gametes that can be formed.

Possibility:1

$\begin{array}{cccc}\text{Parent}& ♂& \text{×}& ♀\\ & \text{Normal chromosome 13}& & \text{Normal chromosome 13}\\ & \text{Normal chromosome 22}& & \text{Normal chromosome 22}\\ & \searrow & & \swarrow \\ \text{Zygote}& & \begin{array}{l}\text{Normal chormosome 13}\\ \text{Normal chormosome 13}\\ \text{Normal chromosome 22}\\ \text{Normal chormosome 22}\end{array}& \end{array}$

Possibility:2

$\begin{array}{cccc}\text{Parent}& ♂& \text{×}& ♀\\ & \text{Normal chromosome 13}& & \text{Normal chromosome 13}\\ & \text{Chromosome 13}+\text{22}& & \text{Normal chromosome 22}\\ & \searrow & & \swarrow \\ \text{Zygote}& & \begin{array}{l}\text{Normal chormosome 13}\\ \text{Normal chromosome 22}\\ \text{Translocated chromosome 22}\\ \text{Chromosome 13}+\text{22}\end{array}& \end{array}$

Possibility:3

$\begin{array}{cccc}\text{Parent}& ♂& \text{×}& ♀\\ & \begin{array}{l}\text{Normal chromosome 13}\\ \text{Chromosome 13}+\text{22}\\ \text{Translocated chromosome 22}\end{array}& & \begin{array}{l}\text{Normal chromosome 13}\\ \text{Normal chromosome 22}\end{array}\\ & & & \\ & \searrow & & \swarrow \\ \text{Zygote}& & \begin{array}{l}\text{Normal chormosome 13}\\ \text{Normal chromosome 22}\\ \text{Normal chromosome 22}\\ \text{Chromosome 13}+\text{22}\end{array}& \end{array}$

Possibility:4

$\begin{array}{cccc}\text{Parent}& ♂& \text{×}& ♀\\ & \text{Normal chromosome 13}& & \text{Normal chromosome 13}\\ & \text{Chromosome 22 is lost}& & \text{Normal chromosome 22}\\ & \searrow & & \swarrow \\ \text{Zygote}& & \begin{array}{l}\text{Normal chormosome 13}\\ \text{Normal chormosome 13}\\ \text{Normal chromosome 22}\end{array}& \end{array}$

Possibility:5

$\begin{array}{cccc}\text{Parent}& ♂& \text{×}& ♀\\ & \begin{array}{l}\text{Normal chromosome 13}\\ \text{Normal chromosome 13}\end{array}& & \text{Normal chromosome 13}\\ & \text{Chromosome 13}+\text{22}& & \text{Normal chromosome 22}\\ & \searrow & & \swarrow \\ \text{Zygote}& & \begin{array}{l}\text{Normal chormosome 13}\\ \text{Normal chormosome 13}\\ \text{Normal chromosome 22}\\ \text{Chromosome13}+\text{22}\end{array}& \end{array}$

Possibility:6

$\begin{array}{cccc}\text{Parent}& ♂& \text{×}& ♀\\ & \text{Chromosome 13 is lost}& & \text{Normal chromosome 13}\\ & \text{Normal chromosome 22}& & \text{Normal chromosome 22}\\ & \searrow & & \swarrow \\ \text{Zygote}& & \begin{array}{l}\text{Normal chormosome 13}\\ \text{Normal chromosome 22}\\ \text{Normal chromosome 22}\end{array}& \end{array}$

c.

Summary Introduction

To explain:

Proportion of surviving offspring expected to be carriers considering that trisomy and monosomy are lethal.

Explanation of Solution

In case, if the trisomy and monosomy of chromosome$13$and chromosome$22$is lethal, then half of the progeny will be carriers for Robertsonian translocation.

Thus, Robertsonian translocation creates a large metacentric chromosome and a fragment that often fails to segregate or chromosome with short arms.