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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Textbook Question
Chapter 10, Problem 1CS
A researcher was asked if his work on human telomere replication was related to any genetic disorders. He replied that one might think that any such mutations would be lethal during early development, but in fact a rare human genetic disorder affecting telomeres is known. This disorder, dyskeratosiscongenita (DKC), is associated with mutations in the protein subunits of telomerase, the enzyme responsible for replicating the ends of eukaryotic chromosomes. Initial symptoms appear in tissues derived from rapidly dividing cells, including the skin, nails, and bone marrow, and first affect children between the ages of 5 and 15 years.
How could such individuals survive?
Expert Solution & Answer
Summary Introduction
To review:
The survivability of people with Dyskeratosis congenita (DKC).
Introduction:
Dyskeratosis congenital (DKC) is a rare genetic X chromosome-linked disease. Initial symptoms of this disease show up between the age of 5 to 15 years. People with DKC has the mutation on telomerase gene thus has non-functional telomerase. This disease affects the tissues with rapidly growing cells like skin, nails, and bone marrow.
Explanation of Solution
The tail region of the eukaryotic chromosome is known as the telomere. This region does not contain any functional genes but only guanine and a cytosine-rich tandem repeat of nucleotides. DNA (deoxyribonucleic acid) polymerase responsible for DNA replication cannot replicate the telomere region efficiently. Thus telomerase play a crucial role in replication of telomere. Here in case of persons withDyskeratosis congenita (DKC), after every successful cell division, a part of the telomere region gets lost in the newly divided cell. This problem is known as end replication problem.
The eukaryotic cells use telomerase to replicate telomere, which can successfully replicate the telomere region without losing any of its regions. The whole telomere region of the people with non-functional telomerase gets lost after a few early cell division. However, as this telomere region does not has any functional genes that could affect the cell functionality, early cell divisions can occur smoothly.
The patients can survive early development. Once the whole telomere region gets lost and functional genes present near the telomere region starts getting lost due to further cell division, only then, the patients show symptoms of DKC. That occursnormally between 5- 15 years of age.
Conclusion
Dyskeratosis congenita (DKC) appears among people who have mutated loss-in-function telomerase. Therefore, it can be concluded that the people with non-functional telomerase can survive early development. After that, they will start showing symptoms ofDKC, which includes nail dystrophy, abnormal skin pigmentation, and bone marrow failure.
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Dyskeratosis congenita (DKC) is a rare human genetic disorderaffecting telomere replication. Mutations in the genesencoding the protein or RNA subunits of telomerase resultin very short telomeres. DKC symptoms include bone marrow failure(reduced production of blood cells) and anemia. If symptoms aresevere, a bone marrow transplant may be the only form of effectivetreatment. In one case, clinicians recommended that a 27-yearoldwoman with a dominant form of DKC undergo a bone marrowtransplant to treat the disorder. Her four siblings were tested, andher 13-year-old brother was identified as the best immunologicallymatched donor. However, before being tested, he was emphaticthat he did not want to know if he had DKC. During testing, it wasdiscovered that he had unusually short telomeres and would mostlikely develop symptoms of DKC.
Although the brother is an immunologically matched donor forhis sister, it would be unethical for the clinicians to transplantbone marrow from the brother to…
Dyskeratosis congenita (DKC) is a rare human genetic disorderaffecting telomere replication. Mutations in the genesencoding the protein or RNA subunits of telomerase resultin very short telomeres. DKC symptoms include bone marrow failure(reduced production of blood cells) and anemia. If symptoms aresevere, a bone marrow transplant may be the only form of effectivetreatment. In one case, clinicians recommended that a 27-yearoldwoman with a dominant form of DKC undergo a bone marrowtransplant to treat the disorder. Her four siblings were tested, andher 13-year-old brother was identified as the best immunologicallymatched donor. However, before being tested, he was emphaticthat he did not want to know if he had DKC. During testing, it wasdiscovered that he had unusually short telomeres and would mostlikely develop symptoms of DKC.
Why might mutations in genes encoding telomerase subunitslead to bone marrow failure?
Explain the connection between defects in DNA repair systemsand the inherited human disease xeroderma pigmentosum.
Chapter 10 Solutions
Essentials of Genetics (9th Edition) - Standalone book
Ch. 10 -
CASE STUDY | At loose ends
A researcher was...Ch. 10 - Prob. 2CSCh. 10 - Prob. 3CSCh. 10 - Prob. 4CSCh. 10 - HOW DO WE KNOW? In this chapter, we focused on how...Ch. 10 - Review the Chapter Concepts list on p. 180. These...Ch. 10 - Compare conservative, semiconservative, and...Ch. 10 - Prob. 4PDQCh. 10 - Predict the results of the experiment by Taylor,...Ch. 10 - Prob. 6PDQ
Ch. 10 - Prob. 7PDQCh. 10 - Prob. 8PDQCh. 10 - Prob. 9PDQCh. 10 - Prob. 10PDQCh. 10 - Prob. 11PDQCh. 10 - Prob. 12PDQCh. 10 - Prob. 13PDQCh. 10 -
14. Distinguish between (a) unidirectional and...Ch. 10 - Prob. 15PDQCh. 10 - Define and indicate the significance of (a)...Ch. 10 - Outline the current model for DNA synthesis.Ch. 10 - Why is DNA synthesis expected to be more complex...Ch. 10 - Prob. 19PDQCh. 10 - Several temperature-sensitive mutant strains of E....Ch. 10 - Prob. 21PDQCh. 10 - Prob. 22PDQ
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