Textbook Question
Telomeres are found at the ends of eukaryotic chromosomes. What is the sequence composition of telomeres?
Ch. 7 - DNA Structure and Replication
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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Table of contents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
Chapter 7, Problem 24
Bloom syndrome (OMIM 210900) is an autosomal recessive disorder caused by mutation of a DNA helicase. Among the principal symptoms of the disease are chromosome instability and a propensity to develop cancer. Explain these symptoms on the basis of the helicase mutation.
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Understand the role of DNA helicase: DNA helicase is an enzyme responsible for unwinding the double-stranded DNA during replication, repair, and recombination. It separates the two strands of DNA by breaking the hydrogen bonds between complementary bases, allowing other enzymes to access the DNA strands.
Explain the impact of helicase mutation: A mutation in the DNA helicase gene can impair the enzyme's ability to unwind DNA properly. This can lead to stalled replication forks, incomplete DNA replication, and errors during DNA repair processes.
Connect helicase dysfunction to chromosome instability: When DNA replication and repair are compromised, it can result in structural abnormalities in chromosomes, such as breaks, deletions, or rearrangements. This is referred to as chromosome instability, which is a hallmark of Bloom syndrome.
Relate chromosome instability to cancer development: Chromosome instability increases the likelihood of mutations and genomic alterations, which can activate oncogenes or inactivate tumor suppressor genes. These changes promote uncontrolled cell growth and contribute to the development of cancer.
Summarize the connection: The symptoms of Bloom syndrome, including chromosome instability and cancer predisposition, can be explained by the defective DNA helicase. This defect disrupts normal DNA replication and repair, leading to genomic instability and an increased risk of tumorigenesis.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
DNA Helicase Function
DNA helicases are essential enzymes that unwind the DNA double helix during replication and repair processes. They separate the two strands of DNA, allowing other proteins to access the genetic information. Mutations in helicase genes can disrupt this unwinding process, leading to errors in DNA replication and repair, which are critical for maintaining genomic stability.
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Chromosome Instability
Chromosome instability refers to an increased rate of chromosomal alterations, such as breaks, rearrangements, or aneuploidy. This instability can arise from defective DNA repair mechanisms, often due to mutations in genes like those encoding helicases. In Bloom syndrome, the inability to properly unwind and repair DNA leads to frequent chromosomal abnormalities, contributing to the disease's symptoms.
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Cancer Propensity
The propensity to develop cancer in individuals with Bloom syndrome is linked to the accumulation of genetic mutations resulting from chromosome instability. When DNA repair processes fail, mutations can accumulate in oncogenes and tumor suppressor genes, leading to uncontrolled cell growth. This increased mutation rate is a hallmark of many cancers, making individuals with Bloom syndrome more susceptible to various malignancies.
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Related Practice
Textbook Question
Raymond Rodriguez and colleagues demonstrated conclusively that DNA replication in E. coli is bidirectional. Explain why locating the origin of replication on one side of the circular chromosomes and the terminus of replication on the opposite side of the chromosome supported this conclusion.
Textbook Question
Joel Huberman and Arthur Riggs used pulse–chase labeling to examine the replication of DNA in mammalian cells. Briefly describe the Huberman–Riggs experiment, and identify how the results exclude a unidirectional model of DNA replication.
Textbook Question
Why do the genomes of eukaryotes, such as Drosophila, need to have multiple origins of replication, whereas bacterial genomes, such as that of E. coli, have only a single origin?
Textbook Question
How does rolling circle replication differ from bidirectional replication?
Textbook Question
Telomeres are found at the ends of eukaryotic chromosomes. How does telomerase assemble telomeres?