What problem with replication of linear chromosomes does telomerase address?

Telomerase is a reverse transcriptase that adds telomeric repeats to the 3′ ends of each chromosome (3). In doing so, telomerase makes up for the shortcomings of semiconservative DNA replication, which cannot complete the synthesis of chromosome ends.

What problem with replication of linear chromosomes does telomerase address quizlet?

What problem with replication of linear chromosomes does telomerase address? The lagging strand stops short of the 3′ end during replication, so chromosomes would shorten in each replication cycle without telomerase.

How does the enzyme telomerase solve the problem of replication at the ends of linear chromosomes?

Telomerase adds complementary RNA bases to the 3′ end of the DNA strand. Once the 3′ end of the lagging strand template is sufficiently elongated, DNA polymerase adds the complementary nucleotides to the ends of the chromosomes; thus, the ends of the chromosomes are replicated. Figure 14.3D.

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What is the end replication problem why in the absence of telomerase do the ends of linear chromosomes get progressively shorter each time the DNA is replicated?

There are ends at the DNA in eukaryotes, unlike the prokaryotic DNA that become shorter after each replication cycle. This is known as the end replication problem. It occurs because the lagging strands of the DNA do not get synthesized for the end of the DNA after the removal of RNA primers.

Why is there a problem replicating the ends of linear DNA?

Unlike bacterial chromosomes, the chromosomes of eukaryotes are linear (rod-shaped), meaning that they have ends. These ends pose a problem for DNA replication. The DNA at the very end of the chromosome cannot be fully copied in each round of replication, resulting in a slow, gradual shortening of the chromosome.

Why do linear chromosomes present a problem during DNA replication quizlet?

Replication of the ends of linear chromosomes pose a challenge because once the last RNA primer is removed from the very end of lagging strand, there is no DNA polymerase that can replace it. Therefore, if no mechanism was available to deal with this problem, the result would be a gap at each end of the chromosome.

Why is there a problem replicating the ends of linear DNA quizlet?

Why is there a problem replicating the ends of linear DNA? The primer used for lagging strand synthesis can’t be replaced because there is no available 3′ OH to add the replacement DNA on to. … The telomeres represent large buffer zones of DNA sequence that do not code for biomolecules.

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Why do telomeres represent a problem for replication and how is this problem solved?

These non-coding sequences at the tips of the chromosomes ensure that the cells will not lose any important genetic function if the telomeres become shorter during every round of replication. … In prokaryotes, the end-replication problem is solved by having circular DNA molecules as chromosomes.

How does telomerase solve end replication problem?

Telomerase is a reverse transcriptase that adds telomeric repeats to the 3′ ends of each chromosome (3). In doing so, telomerase makes up for the shortcomings of semiconservative DNA replication, which cannot complete the synthesis of chromosome ends.

What is the end replication problem and how does telomerase help solve this problem?

For example, the end replication problem causes a progressive shortening of telomeric DNA at each round of DNA replication, thus telomeres eventually lose their protective capacity. This phenomenon is counteracted by the recruitment and the activation at telomeres of the specialized reverse transcriptase telomerase.

Why are telomeres problematic for eukaryotic chromosome replication?

Why are telomeres problematic for eukaryotic chromosome replication? Removal of the lagging strand primer leaves a gap in the one of the strand’s DNA sequences.

How telomeres solve the end protection problem?

Telomeres solve this end-protection problem by repressing all forms of DDR signaling and DSB repair. The telomeric DNA, maintained by telomerase, binds a six-subunit protein complex, termed shelterin, that protects chromosome ends.

What is the end replication problem?

The end replication problem hypothesis proposes that the ends of linear DNA cannot be replicated completely during lagging strand DNA synthesis. Although the idea has been widely accepted for explaining telomere attrition during cell proliferation, it has never been directly demonstrated.

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How does telomerase assemble telomeres?

How does telomerase assemble telomeres? Telomerase uses a segment of its RNA as the template to add multiple copies of a simple sequence to the 3′ end of each strand of DNA on a linear chromosome. This strand is copied by the normal mechanism of lagging strand synthesis after it is extended by telomerase.

What is the role of telomerase RNA in the telomere replenishing?

One solution to this end replication problem is the ribonucleoprotein (RNP) complex, telomerase. Telomerase compensates for telomere erosion by replenishing the sequence repeats (TTAGGG in humans) at the 3′ end of telomeric DNA (16).

Why is telomerase a reverse transcriptase?

The human telomerase reverse-transcriptase (TERT) gene encodes a rate-limiting catalytic subunit of telomerase, which maintains the length of telomeric DNA and chromosomal stability. Thus, TERT plays a pivotal role in cellular immortalization, cancer development and progression.