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Chapter 11: Problem 24

In \(1994,\) telomerase activity was discovered in human cancer cell lines. Although telomerase is not active in human somatic tissue, this discovery indicated that humans 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.

Short Answer

Expert verified
Answer: Telomerase activation is advantageous or necessary in germ cells, stem cells, and immune cells. It is crucial for maintaining telomeres and genomic stability, ensuring continued reproduction, tissue repair, and immune responses. Despite the potential involvement of telomerase in cancer, the benefits of telomerase activation in these specific cells justify the preservation of telomerase genes in the human genome throughout evolution.

Step by step solution

01

Understand the Function of Telomerase

Telomerase is an enzyme that adds specific DNA sequence repeats to the ends of chromosomes, called telomeres. Telomeres protect the ends of chromosomes from degradation and ensure genomic stability. In the absence of telomerase, when a cell divides, its telomeres shorten, and eventually, the cell reaches a state of senescence leading to aging and other age-related diseases.
02

Role of Telomerase in Normal Human Cells

Since telomerase is not active in most human somatic tissues, meaning that the telomeres will continue to shorten with each cell division, leading to cell senescence or apoptosis. There are some exceptions where telomerase activity is present, such as germ cells, stem cells, and immune cells. In these cells, telomerase helps maintain their telomere length and ensures genomic stability, allowing these cells to divide for long periods of time.
03

Explain the Advantages/Necessity of Telomerase Activation

Telomerase activation can be advantageous or necessary in certain types of human body cells: 1. Germ cells: Telomerase keeps telomeres intact during embryonic development, providing ongoing reproductive capabilities for the organism. 2. Stem cells: Both adult and embryonic stem cells have active telomerase, allowing them to maintain their telomeres, proliferate, and differentiate under proper conditions. 3. Immune cells: Some immune cells exhibit telomerase activity, enabling them to proliferate rapidly when needed to combat pathogens. The maintenance of telomerase in specific cells enables proper cellular function.
04

Reason for Maintaining Telomerase Genes in the Human Genome

Despite the link between telomerase activation and cancer, it's essential for the human genome to preserve the genes coding for this enzyme. The critical functions of telomerase in germ cells, stem cells, and immune cells contribute to continued reproduction, tissue repair, and immune responses. The benefits of maintaining telomerase activity in these specific cells justify the preservation of the telomerase genes in the human genome throughout evolution.
05

Concluding Remarks

In conclusion, while telomerase activation may contribute to cancer, its essential roles in germ cells, stem cells, and immune cells make it necessary to maintain the telomerase genes in the human genome. The activation of telomerase in these cells allows for the preservation of telomere length and genomic stability, ensuring continuous reproduction, tissue repair, and immune responses.

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Most popular questions from this chapter

During DNA replication, which enzyme can be disposed of in an organism with a mutant DNA polymerase that does not require a free \(3^{\prime}-\mathrm{OH} ?\)

Distinguish between (a) unidirectional and bidirectional synthesis, and (b) continuous and discontinuous synthesis of DNA.

In this chapter, we focused on how DNA is replicated and synthesized. We also discussed recombination at the DNA level and the phenomenon of gene conversion. Along the way, we encountered many opportunities to consider how this information was acquired. On the basis of these discussions, what answers would you propose to the following fundamental questions? (a) What is the experimental basis for concluding that DNA replicates semiconservatively in both prokaryotes and eukaryotes? (b) How was it demonstrated that DNA synthesis occurs under the direction of DNA polymerase III and not polymerase I? (c) How do we know that in vivo DNA synthesis occurs in the \(5^{\prime}\) to \(3^{\prime}\) direction? (d) How do we know that DNA synthesis is discontinuous on one of the two template strands? (e) What observations reveal that a "telomere problem" exists during eukaryotic DNA replication, and how did we learn of the solution to this problem?

Suppose that \(E .\) coli synthesizes DNA at a rate of 100,000 nucleotides per minute and takes 40 minutes to replicate its chromo- some. (a) How many base pairs are present in the entire \(E .\) coli chromosome? (b) What is the physical length of the chromosome in its helical configuration- that is, what is the circumference of the chromosome if it were opened into a circle?

Review the Chapter Concepts list on \(\mathrm{p} .295 .\) These are concerned with the replication and synthesis of DNA. Write a short essay that distinguishes between the terms replication and synthesis, as applied to DNA. Which of the two is most closely allied with the field of biochemistry?
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