Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 4: Problem 33

Two mothers give birth to sons at the same time at a busy urban hospital. The son of mother 1 is afflicted with hemophilia, a disease caused by an X-linked recessive allele. Neither parent has the disease. Mother 2 has a normal son, despite the fact that the father has hemophilia. Several years later, couple 1 sues the hospital, claiming that these two newborns were swapped in the nursery following their birth. As a genetic counselor, you are called to testify. What information can you provide the jury concerning the allegation?

Short Answer

Expert verified
Answer: No, the likelihood that the sons were swapped at birth is low. The outcomes are consistent with the expected probabilities for each couple.

Step by step solution

01

Understand X-linked inheritance

Hemophilia is an X-linked recessive disease, meaning that the gene responsible for the disease is located on the X chromosome. In this case, the affected allele will be labeled as "h", and the non-affected allele as "H". Since males have one X chromosome and one Y chromosome (XY), they will be affected by hemophilia if they inherit the X chromosome with the recessive allele (XhY). Females have two X chromosomes (XX), and can only have the disease if they inherit the affected allele from both parents (XhXh); otherwise, they will be carriers (XHXh) or non-carriers (XHXH).
02

Determine the genotypes of the parents

To determine the possible outcomes for their offspring, we first need to know the genotype of each individual in both families. Couple 1: - Mother 1: We're told that she is not affected by hemophilia, but her son is affected. This means she must be a carrier (XHXh). - Father 1: He's not affected, meaning he's genotypically XHY. Couple 2: - Mother 2: Her son is healthy, but his father is affected. We are not given information about whether she's a carrier or not, so we'll assume her genotype is XHXH (non-carrier) for this part of the analysis. - Father 2: He has hemophilia, meaning he has the XhY genotype.
03

Determine the possible offspring genotypes

Next, we will determine the possible offspring genotypes for each couple using Punnett squares. Couple 1 (Mother 1: XHXh, Father 1: XHY): - Offspring genotypes: XHXH (25%), XHXh (25%), XHY (25%), and XhY (25%) - Probability of having a son with hemophilia: 25% Couple 2 (Mother 2: XHXH, Father 2: XhY): - Offspring genotypes: XHXh (50%) and XHY (50%) - Probability of having a healthy son: 50%
04

Compare the expected offspring outcomes

Couple 1 has a 25% probability of having a son with hemophilia, which supports the fact that their son has the disease. Couple 2 has a 50% probability of having a healthy son, so their son being unaffected is also consistent with the probabilities.
05

Assess the likelihood of the allegation

Based on the genetic information provided and our analysis of X-linked inheritance, the swap allegation seems unlikely since the outcomes are consistent with the expected probabilities for each couple. However, additional genetic testing may be needed to provide more definitive information. Without evidence, as a genetic counselor, the information provided to the jury would be that based on the inheritance pattern of hemophilia and the genotypes of the parents, the likelihood that the sons were swapped at birth is low.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

The trait of medium-sized leaves in iris is determined by the genetic condition \(P P\) '. Plants with large leaves are \(P P\), whereas plants with small leaves are \(P^{\prime} P^{\prime} . A\) cross is made between two plants each with medium-sized leaves. If they produce 80 seedlings, what would be the expected phenotypes, and in what numbers would they be expected? What is the term for this allelic relationship?

Review the Chapter Concepts list on page \(104 .\) These all relate to exceptions to the inheritance patterns encountered by Mendel. Write a short essay that explains why multiple and lethal alleles often result in a modification of the classic Mendelian monohybrid and dihybrid ratios.

Proto-oncogenes stimulate cells to progress through the cell cycle and begin mitosis. In cells that stop dividing, transcription of proto-oncogenes is inhibited by regulatory molecules. As is typical of all genes, proto-oncogenes contain a regulatory DNA region followed by a coding DNA region that specifies the amino acid sequence of the gene product. Consider two types of mutation in a proto-oncogene, one in the regulatory region that eliminates transcriptional control and the other in the coding region that renders the gene product inactive. Characterize both of these mutant alleles as either gain-of-function or loss-of-function mutations and indicate whether each would be dominant or recessive.

Discuss how temperature influences phenotypic expression.

In humans, the \(A B O\) blood type is under the control of autosomal multiple alleles. Color blindness is a recessive X-linked trait. If two parents who are both type \(A\) and have normal vision produce a son who is color-blind and is type \(\mathrm{O},\) what is the probability that their next child will be a female who has normal vision and is type \(\mathrm{O} ?\)
See all solutions

Recommended explanations on Biology Textbooks

Biology Experiments

Read Explanation

Responding to Change

Read Explanation

Microbiology

Read Explanation

Biological Structures

Read Explanation

Biological Organisms

Read Explanation

Cellular Energetics

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free