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Chapter 10: Problem 23

Describe the "end-replication problem" in eukaryotes. How is it resolved?

Short Answer

Expert verified
Answer: Telomerase is a specialized enzyme found in eukaryotic cells that can resolve the end-replication problem by extending the telomeres. It contains its own RNA template and uses this template to synthesize the repetitive DNA sequences of the telomeres. By extending the telomeric region, telomerase provides more space for the lagging strand synthesis to take place, thus preventing the loss of vital genetic information during DNA replication.

Step by step solution

01

Background on DNA replication

DNA replication in eukaryotic cells is a complex process involving the unwinding of the DNA double helix and using each strand as a template to synthesize a new complementary strand. The enzyme DNA polymerase III adds nucleotides to the new strand in a 5' to 3' direction.
02

The end-replication problem

The end-replication problem arises because DNA polymerase III can only synthesize DNA in the 5' to 3' direction. This creates a situation where leading strand replication can continue uninterrupted until the chromosome end, while the lagging strand replication leaves small gaps on the 3' end. These gaps result from the removal of RNA primers, which are necessary for initiating DNA synthesis on the lagging strand. Eventually, after multiple rounds of replication, this loss of genetic material leads to shorter chromosomes.
03

Role of telomeres

Telomeres are repetitive nucleotide sequences located at the ends of chromosomes that protect the chromosomes from degradation and loss of vital genetic information. They also prevent chromosomes from fusing with one another, which could cause genomic instability and other problems.
04

The role of telomerase

Telomerase is a specialized enzyme found in eukaryotic cells that can resolve the end-replication problem. It contains its own RNA template and uses this template to synthesize the repetitive DNA sequences of the telomeres. By extending the telomeric region, telomerase provides more space for the lagging strand synthesis to take place, thus preventing the loss of vital genetic information during DNA replication.
05

Overall resolution of the end-replication problem

In summary, the end-replication problem in eukaryotes is resolved by the presence of telomeres and the activity of the enzyme telomerase. Telomeres protect the chromosome ends from degradation, and telomerase replenishes the lost nucleotides during replication, ensuring the stability and integrity of the genetic material in eukaryotic cells.

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Most popular questions from this chapter

Why is DNA synthesis expected to be more complex in eukaryotes than in bacteria? How is DNA synthesis similar in the two types of organisms?

If the analysis of DNA from two different microorganisms demonstrated very similar base compositions, are the DNA sequences of the two organisms also nearly identical?

Describe the role of \(^{15} \mathrm{N}\) in the Meselson-Stahl experiment.

Define and indicate the significance of (a) Okazaki fragments, (b) DNA ligase, and (c) primer RNA during DNA replication.

Many of the gene products involved in DNA synthesis were initially defined by studying mutant \(E .\) coli strains that could not synthesize DNA. (a) The dnaE gene encodes the \(\alpha\) subunit of DNA polymerase III. What effect is expected from a mutation in this gene? How could the mutant strain be maintained? (b) The \(d n a Q\) gene encodes the \(\varepsilon\) subunit of DNA polymerase. What effect is expected from a mutation in this gene?
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