EBK CONCEPTS OF GENETICS
12th Edition
ISBN: 9780134818979
Author: Killian
Publisher: YUZU
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Chapter 15, Problem 1CS
Six months pregnant, an expectant mother had a routine ultrasound that showed that the limbs of the fetus were unusually short. Her physician suspected that the baby might have a genetic form of dwarfism called achondroplasia, an autosomal dominant trait occurring with a frequency of about 1 in 27,000 births. The parents were directed to a genetic counselor to discuss this diagnosis. In the conference, they learned that achondroplasia is caused by a mutant allele. Sometimes it is passed from one generation to another, but in 80 percent of all cases it is the result of a spontaneous mutation that arises in a gamete of one of the parents. They also learned that most children with achondroplasia have normal intelligence and a normal life span.
What information would be most relevant to concluding which of the two mutation origins, inherited or new, most likely pertains in this case? How does this conclusion impact on this couple's decision to have more children?
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Achondroplasia is an autosomal dominant disorder characterized by disproportionate short stature: the legs and arms of people with achondroplasia are short compared with the head and trunk. The disorder is due to a base substitution in the gene, located on the short arm of chromosome 4, that encodes fibroblast growth factor receptor 3 (FGFR3). Although achondroplasia is clearly inherited as an autosomal dominant trait, more than 80% of the people who have achondroplasia are born to parents with normal stature. This high percentage indicates that most cases are caused by newly arising mutations; these cases (not inherited from an affected parent) are referred to as sporadic. Studies have demonstrated that sporadic cases of achondroplasia are almost always caused by mutations inherited from the father (paternal mutations). In addition, the occurrence of achondroplasia is higher among the children of older fathers; approximately 50% of children with achondroplasia are born to fathers…
A couple is planning a family, but since each has a brother having the sickle-cell disorder, they are worried that their kids might develop the disorder too. Neither of them nor their respective parents have the disorder. Which of the following will be your smartest advice as a genetic counsellor?
One of four of their children can be expected to have sickle cell.
It is possible that none of their kids will have the disorder, but tests should be carried out on both of them to confirm.
All of their children will have sickle-cell disorder.
There is no chance of any of their kids having sickle cell.
A man and a woman have a child with cystic fibrosis. Neither parent has cystic fibrosis. How could this happen?
a) Both parents carry the cystic fibrosis allele, and each passed that allele to their child.
b) The child had a spontaneous mutation on both copies of their CFTR alleles, leading to cystic fibrosis.
c) One parent gave the child two copies of the cystic fibrosis CFTR allele.
c) One parent gave the child a wild type CFTR allele, and the other parent gave them a cystic fibrosis CFTR gene.
Chapter 15 Solutions
EBK CONCEPTS OF GENETICS
Ch. 15 - If a point mutation occurs within a human egg cell...Ch. 15 - One of the most famous cases of an X-linked...Ch. 15 - The cancer drug melphalan is an alkylating agent...Ch. 15 - Geneticists often use the alkylating agent...Ch. 15 - Six months pregnant, an expectant mother had a...Ch. 15 - Six months pregnant, an expectant mother had a...Ch. 15 - HOW DO WE KNOW? In this chapter, we focused on how...Ch. 15 - CONCEPT QUESTION Review the Chapter Concepts list...Ch. 15 - What is a spontaneous mutation, and why are...Ch. 15 - Prob. 4PDQ
Ch. 15 - Prob. 5PDQCh. 15 - Why is a random mutation more likely to be...Ch. 15 - Most mutations in a diploid organism are...Ch. 15 - What is the difference between a silent mutation...Ch. 15 - Describe a tautomeric shift and how it may lead to...Ch. 15 - Contrast and compare the mutagenic effects of...Ch. 15 - Why are frameshift mutations likely to be more...Ch. 15 - Why are X rays more potent mutagens than UV...Ch. 15 - DNA damage brought on by a variety of natural and...Ch. 15 - Contrast the various types of DNA repair...Ch. 15 - Mammography is an accurate screening technique for...Ch. 15 - A significant number of mutations in the HBB gene...Ch. 15 - Describe how the Ames test screens for potential...Ch. 15 - Prob. 18PDQCh. 15 - Compare DNA transposons and retrotransposons. What...Ch. 15 - Prob. 20PDQCh. 15 - In maize, a Ds or Ac transposon can alter the...Ch. 15 - Prob. 22PDQCh. 15 - In a bacterial culture in which all cells are...Ch. 15 - Presented here are hypothetical findings from...Ch. 15 - Prob. 25ESPCh. 15 - Prob. 26ESPCh. 15 - What evidence indicates that mutations in human...Ch. 15 - Among Betazoids in the world of Star Trek, the...Ch. 15 - Skin cancer carries a lifetime risk nearly equal...Ch. 15 - It has been noted that most transposons in humans...Ch. 15 - Mutations in the IL2RG gene cause approximately 30...
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