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Ch. 11 - DNA Replication and Recombination
Chapter 11, Problem 26

At the end of the short arm of human chromosome 16 (16p), several genes associated with disease are present, including thalassemia and polycystic kidney disease. When that region of chromosome 16 was sequenced, gene-coding regions were found to be very close to the telomere-associated sequences. Could there be a possible link between the location of these genes and the presence of the telomere-associated sequences? What further information concerning the disease genes would be useful in your analysis?

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Consider the role of telomeres in protecting chromosome ends and their potential influence on nearby gene expression.
Investigate whether the proximity of genes to telomeres affects their regulation or expression, possibly through telomere position effect (TPE).
Examine the specific functions and expression patterns of the disease-associated genes located near the telomere on chromosome 16.
Research any known interactions between telomere-associated sequences and the regulatory elements of the disease genes.
Gather information on any genetic or epigenetic modifications in the region that might influence gene expression or contribute to disease phenotypes.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Telomeres

Telomeres are repetitive nucleotide sequences located at the ends of chromosomes, protecting them from degradation and preventing the loss of genetic information during cell division. They play a crucial role in maintaining chromosome stability and integrity. The proximity of gene-coding regions to telomeres may influence gene expression and stability, potentially linking telomere dynamics to disease susceptibility.
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Gene Location and Expression

The physical location of genes on chromosomes can significantly affect their expression and regulation. Genes situated near telomeres may experience different epigenetic modifications compared to those located in central chromosomal regions. Understanding the spatial organization of genes can provide insights into how their expression is regulated and how this may relate to disease mechanisms.
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Genetic Association Studies

Genetic association studies investigate the relationship between specific genetic variants and diseases. These studies can help identify whether certain genes, particularly those located near telomeres, are associated with increased risk for conditions like thalassemia and polycystic kidney disease. Further information, such as variant frequency and functional studies, would enhance the understanding of how these genes contribute to disease pathology.
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Related Practice
Textbook Question
In 1994, telomerase activity was discovered in human cancer cell lines. Although telomerase is not active in most human adult cells, all cells do contain the genes for telomerase proteins and telomerase RNA. Since inappropriate activation of telomerase may contribute to cancer, why do you think the genes coding for this enzyme have been maintained in the human genome throughout evolution? Are there any types of human body cells where telomerase activation would be advantageous or even necessary? Explain.
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Textbook Question
The genome of D. melanogaster consists of approximately 1.7x10⁸ base pairs. DNA synthesis occurs at a rate of 30 base pairs per second. In the early embryo, the entire genome is replicated in five minutes. How many bidirectional origins of synthesis are required to accomplish this feat?
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Textbook Question
Assume a hypothetical organism in which DNA replication is conservative. Design an experiment similar to that of Taylor, Woods, and Hughes that will unequivocally establish this fact. Using the format established in Figure 11.5, draw sister chromatids and illustrate the expected results establishing this mode of replication.
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Textbook Question
DNA polymerases in all organisms add only 5' nucleotides to the 3' end of a growing DNA strand, never to the 5' end. One possible reason for this is the fact that most DNA polymerases have a proofreading function that would not be energetically possible if DNA synthesis occurred in the 3' to 5' direction. Sketch the reaction that DNA polymerase would have to catalyze if DNA synthesis occurred in the 3' to 5' direction.
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Textbook Question
DNA polymerases in all organisms add only 5' nucleotides to the 3' end of a growing DNA strand, never to the 5' end. One possible reason for this is the fact that most DNA polymerases have a proofreading function that would not be energetically possible if DNA synthesis occurred in the 3' to 5' direction. Consider the information in your sketch and speculate as to why proofreading would be problematic.
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Textbook Question
Assume that the sequence of bases shown below is present on one nucleotide chain of a DNA duplex and that the chain has opened up at a replication fork. Synthesis of an RNA primer occurs on this template starting at the base that is underlined. If the RNA primer consists of eight nucleotides, what is its base sequence?
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