Essentials of Genetics (9th Edition) - Standalone book
9th Edition
ISBN: 9780134047799
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino
Publisher: PEARSON
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Chapter 22, Problem 19PDQ
A form of dwarfism known as Ellis–van Creveld syndrome was first discovered in the late 1930s, when Richard Ellis and Simon van Creveld shared a train compartment on the way to a pediatrics meeting. In the course of conversation, they discovered that they each had a patient with this syndrome. They published a description of the syndrome in 1940. Affected individuals have a short-limbed form of dwarfism and often have defects of the lips and teeth, and polydactyly (extra fingers). The largest pedigree for the condition was reported in an Old Order Amish population in eastern Pennsylvania by Victor McKusick and his colleagues (1964). In that community, about 5 per 1000 births are affected, and in the population of 8000, the observed frequency is 2 per 1000. All affected individuals have unaffected parents, and all affected cases can trace their ancestry to Samuel King and his wife, who arrived in the area in 1774. It is known that neither King nor his wife was affected with the disorder. There are no cases of the disorder in other Amish communities, such as those in Ohio or Indiana.
(a) From the information provided, derive the most likely mode of inheritance of this disorder. Using the Hardy–Weinberg law, calculate the frequency of the mutant allele in the population and the frequency of heterozygotes, assuming Hardy–Weinberg conditions.
(b) What is the most likely explanation for the high frequency of the disorder in the Pennsylvania Amish community and its absence in other Amish communities?
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In a study of a muscle disorder, several affected families exhibited vision problems, muscle weakness, and deafness (M. Zeviani et al. 1990. American Journal of Human Genetics 47:904–914). Analysis of the mtDNA from affected members of these families revealed that large numbers of their mtDNA molecules possessed deletions of varying lengths. Different members of the same family and even different mitochondria from the same person possessed deletions of different sizes, so the underlying defect appeared to be a tendency for the mtDNA of affected persons to have deletions. A pedigree of one of the families studied is shown below. The researchers concluded that this disorder is inherited as an autosomal dominant trait, and they mapped the diseasecausing gene to a position on chromosome 10 in the nucleus.
Q. What characteristics of the pedigree rule out inheritance of a trait encoded by a gene in the mtDNA as the cause of this disorder?
Chapter 22 Solutions
Essentials of Genetics (9th Edition) - Standalone book
Ch. 22 - CASE STUDY |An unexpected outcome A newborn...Ch. 22 - CASE STUDY |Anunexpected outcome A newborn...Ch. 22 - CASE STUDY|An unexpected outcome A newborn...Ch. 22 - HOW DO WE KNOW? Population geneticists study...Ch. 22 - Review the Chapter Concepts on page 441. All these...Ch. 22 -
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4. The genetic difference between two Drosophila...Ch. 22 - The use of nucleotide sequence data to measure...Ch. 22 - Calculate the frequencies of the AA, Aa, and aa...Ch. 22 - Prob. 7PDQ
Ch. 22 -
8. What must be assumed in order to validate the...Ch. 22 - In a population where only the total number of...Ch. 22 -
10. If 4 percent of a population in equilibrium...Ch. 22 -
11. Consider a population in which the frequency...Ch. 22 - If the initial allele frequencies are p = 0.5 and...Ch. 22 -
13. Under what circumstances might a lethal...Ch. 22 - Assume that a recessive autosomal disorder occurs...Ch. 22 -
15. One of the first Mendelian traits identified...Ch. 22 -
16. Describe how populations with substantial...Ch. 22 - Achondroplasia is a dominant trait that causes a...Ch. 22 -
18. A recent study examining the mutation rates...Ch. 22 - A form of dwarfism known as Ellis–van Creveld...Ch. 22 -
20. List the barriers that prevent interbreeding...Ch. 22 - What are the two groups of reproductive isolating...Ch. 22 - Prob. 22PDQCh. 22 -
23. In a recent study of cichlid fish inhabiting...Ch. 22 - What genetic changes take place during speciation?Ch. 22 - Some critics have warned that the use of gene...Ch. 22 - Comparisons of Neanderthal mitochondrial DNA with...
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