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Ch. 3 - Cell Division and Chromosome Heredity
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 3 - Cell Division and Chromosome HeredityProblem 13b
Chapter 3, Problem 13b

In humans, hemophilia A (OMIM 306700) is an X-linked recessive disorder that affects the gene for factor VIII protein, which is essential for blood clotting. The dominant and recessive alleles for the factor VIII gene are represented by H and h. Albinism is an autosomal recessive condition that results from mutation of the gene producing tyrosinase, an enzyme in the melanin synthesis pathway. A and a represent the tyrosinase alleles. A healthy woman named Clara (II-2), whose father (I-1) has hemophilia and whose brother (II-1) has albinism, is married to a healthy man named Charles (II-3), whose parents are healthy. Charles's brother (II-5) has hemophilia, and his sister (II-4) has albinism. The pedigree is shown below.
Pedigree chart showing inheritance patterns of hemophilia and albinism in Clara and Charles's family.
Determine the probability that the first child of Clara and Charles will be a


i. boy with hemophilia
ii. girl with albinism
iii. healthy girl
iv. boy with both albinism and hemophilia
v. boy with albinism
vi. girl with hemophilia

Verified step by step guidance
1
Step 1: Understand the genetic inheritance patterns. Hemophilia A is X-linked recessive, meaning males (XY) inherit the condition if they receive the recessive allele (h) on their X chromosome. Females (XX) must inherit two recessive alleles (hh) to express the condition. Albinism is autosomal recessive, meaning an individual must inherit two recessive alleles (aa) to express the condition.
Step 2: Determine the genotypes of Clara and Charles based on the pedigree. Clara's father has hemophilia (X^hY), so Clara must be a carrier (X^HX^h). Clara's brother has albinism (aa), so Clara must be heterozygous for albinism (Aa). Charles's brother has hemophilia (X^hY), so Charles must have inherited a normal X chromosome (X^HY). Charles's sister has albinism (aa), so Charles must also be heterozygous for albinism (Aa).
Step 3: Set up Punnett squares for each trait. For hemophilia, cross Clara's X^HX^h with Charles's X^HY to determine the probabilities of their children inheriting hemophilia. For albinism, cross Clara's Aa with Charles's Aa to determine the probabilities of their children inheriting albinism.
Step 4: Combine the probabilities from the Punnett squares. Since hemophilia and albinism are inherited independently, multiply the probabilities of each condition to determine the likelihood of a child having both traits or being healthy. For example, the probability of a boy with hemophilia and albinism is the product of the probability of being male (50%), having hemophilia (from the X-linked Punnett square), and having albinism (from the autosomal Punnett square).
Step 5: Use the combined probabilities to answer each part of the question. For example, calculate the probability of a boy with hemophilia (i), a girl with albinism (ii), a healthy girl (iii), a boy with both albinism and hemophilia (iv), a boy with albinism (v), and a girl with hemophilia (vi). Ensure that the probabilities are consistent with the inheritance patterns and the genotypes of Clara and Charles.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

X-linked Recessive Inheritance

X-linked recessive inheritance refers to genetic conditions that are associated with genes located on the X chromosome. In this mode of inheritance, males (XY) are more likely to express the disorder because they have only one X chromosome. Females (XX) can be carriers if they have one affected X chromosome and one normal X chromosome, but they typically do not express the disorder unless both X chromosomes are affected.
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Autosomal Recessive Inheritance

Autosomal recessive inheritance involves genes located on non-sex chromosomes (autosomes). For an individual to express an autosomal recessive condition, they must inherit two copies of the mutated gene, one from each parent. Carriers, who have only one copy of the mutated gene, do not show symptoms but can pass the allele to their offspring, making it crucial to understand family history when assessing risk.
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Punnett Squares and Probability

Punnett squares are a tool used in genetics to predict the probability of offspring inheriting particular traits based on the genetic makeup of the parents. By filling out a Punnett square with the alleles of each parent, one can visualize the potential combinations of alleles in the offspring, allowing for the calculation of probabilities for specific traits, such as hemophilia or albinism in this scenario.
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Related Practice
Textbook Question

A woman's father has ornithine transcarbamylase deficiency (OTD), an X-linked recessive disorder producing mental deterioration if not properly treated. The woman's mother is homozygous for the wild-type allele.


Identify a male with whom the woman could produce a daughter with OTD.

Textbook Question

A woman's father has ornithine transcarbamylase deficiency (OTD), an X-linked recessive disorder producing mental deterioration if not properly treated. The woman's mother is homozygous for the wild-type allele.


What proportion of daughters produced by the woman and the man are expected to have OTD? What proportion of sons of the woman and the man are expected to have OTD?

Textbook Question

In humans, hemophilia A (OMIM 306700) is an X-linked recessive disorder that affects the gene for factor VIII protein, which is essential for blood clotting. The dominant and recessive alleles for the factor VIII gene are represented by H and h. Albinism is an autosomal recessive condition that results from mutation of the gene producing tyrosinase, an enzyme in the melanin synthesis pathway. A and a represent the tyrosinase alleles. A healthy woman named Clara (II-2), whose father (I-1) has hemophilia and whose brother (II-1) has albinism, is married to a healthy man named Charles (II-3), whose parents are healthy. Charles's brother (II-5) has hemophilia, and his sister (II-4) has albinism. The pedigree is shown below.

What are the genotypes of the four parents (I-1 to I-4) in this pedigree?

Textbook Question

In humans, hemophilia A (OMIM 306700) is an X-linked recessive disorder that affects the gene for factor VIII protein, which is essential for blood clotting. The dominant and recessive alleles for the factor VIII gene are represented by H and h. Albinism is an autosomal recessive condition that results from mutation of the gene producing tyrosinase, an enzyme in the melanin synthesis pathway. A and a represent the tyrosinase alleles. A healthy woman named Clara (II-2), whose father (I-1) has hemophilia and whose brother (II-1) has albinism, is married to a healthy man named Charles (II-3), whose parents are healthy. Charles's brother (II-5) has hemophilia, and his sister (II-4) has albinism. The pedigree is shown below.

If Clara and Charles's first child has albinism, what is the chance the second child has albinism? Explain why this probability is higher than the probability you calculated in part (b).

Textbook Question

A wild-type male and a wild-type female Drosophila with red eyes and full wings are crossed. Their progeny are shown below.

Using clearly defined allele symbols of your choice, give the genotype of each parent.

Textbook Question

A wild-type male and a wild-type female Drosophila with red eyes and full wings are crossed. Their progeny are shown below.

What is/are the genotype(s) of females with purple eye? Of males with purple eye and miniature wing?