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Chapter 4: Problem 27

A sex-influenced trait in humans affects the length of the index finger. A short allele is dominant in males and recessive in females. Heterozygous males have an index finger that is significantly shorter than the ring finger. The gene affecting index finger length is located on an autosome. A woman with short index fingers has children with a man who has normal index fingers. They produce five children in the following order: female, male, male, female, male. The oldest female offspring has one daughter with a man who has normal fingers. The youngest male among the five children has children with a woman with short index fingers; they have two sons. Draw the pedigree for this family. Indicate the phenotypes of every individual (filled symbols for individuals with short index fingers and open symbols for individuals with normal index fingers).

Short Answer

Expert verified
The constructed pedigree chart should have a filled circle for the mother and an open square for the father as parents. Their children should consist of two open circle (females with normal fingers) and three filled squares (males with short fingers). The oldest female (an open circle) should be connected with an open square to produce another open circle as offspring. The youngest male (a filled square) should be connected with a filled circle to produce two filled squares.

Step by step solution

01

Identify the Parents

From the problem, the initial generation consists of a female with short index fingers (recessive trait) and a male with normal index fingers (dominant trait). So, the mother is represented by a filled circle and the father by an open square.
02

Map the Children

Their offspring are three males and two females. The females would have the dominant trait (normal fingers) as they will inherit one short index finger allele from their mother and one normal allele from their father (heterozygous), that would express itself as normal finger length in females. The males would be similar to the mother due to the inheritance pattern. Thus, they are represented by open circles and filled squares, respectively.
03

Representation of Grandchildren

The oldest female offspring has a daughter with a man who has normal fingers. They would produce a female child with normal index fingers. The youngest male has children with a woman with short index fingers; they have two sons. The sons would inherit the short finger trait from the father and are represented by filled squares.

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Most popular questions from this chapter

Incontinentia pigmenti, a rare, X-linked dominant disorder in humans, is characterized by swirls of pigment in the skin. If an affected female, who had an unaffected father, has children with an unaffected male, what are the predicted ratios of affected and unaffected sons and daughters?

The blood serum from one individual (let's call this person individual 1 ) is known to agglutinate the red blood cells from a second individual (individual 2). List the pairwise combinations of possible genotypes that individuals 1 and 2 could have. If individual 1 is the parent of individual 2, what are his or her possible genotypes?

In rabbits, the color of body fat is controlled by a single gene with two alleles, designated \(Y\) and \(y\). The outcome of this trait is affected by the diet of the rabbit. When raised on a standard vegetarian diet, the dominant \(Y\) allele confers white body fat, and the \(y\) allele confers yellow body fat. However, when raised on a xanthophyll-free diet, a homozygote \(y y\) rabbit has white body fat. If a heterozygous rabbit is crossed to a rabbit with yellow body fat, what are the proportions of offspring with white and yellow body fat when raised on a standard vegetarian diet? How do the proportions change if the offspring are raised on a xanthophyll-free diet?

In humans, a very rare dominant allele that causes the little finger to be crooked has a penetrance of \(80 \%\). In other words, \(80 \%\) of heterozygotes carrying the allele will have a crooked little finger. If a homozygous unaffected person has children with a heterozygote carrying this mutant allele, what is the probability that an offspring will have a little finger that is crooked?

A nectarine is a peach without the fuzz. The difference is controlled by a single gene that is found in two alleles, \(D\) and \(d\). At the molecular level, do you think that the nectarine is homozygous for a recessive allele or that the peach is homozygous for the recessive allele? Explain your reasoning.
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