Why do chromosomes shorten at each replication?

Why does the code shorten after every replication?

Every time a cell? carries out DNA replication? the chromosomes are shortened by about 25-200 bases (A, C, G, or T) per replication. However, because the ends are protected by telomeres, the only part of the chromosome that is lost, is the telomere, and the DNA is left undamaged.

Why do telomeres shorten with each round of replication?

At each cell division, the telomeres shorten because of the incomplete replication of the linear DNA molecules by the conventional DNA polymerases. … This is specifically due to the resection and fill-in reaction during the synthesis of the telomere leading-strand [7,8].

Why do telomeres get shorter?

Telomere length shortens with age. Rate of telomere shortening may indicate the pace of aging. Lifestyle factors such as smoking, lack of physical activity, obesity, stress, exposure to pollution, etc. can potentially increase the rate of telomere shortening, cancer risk, and pace of aging.

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Why is the daughter strand shorter?

However, there is no more DNA in the 5′ direction after the final RNA primer, so DNA polymerse cannot replace the RNA with DNA. Therefore, both daughter DNA strands have an incomplete 5′ strand with 3′ overhang. … Each daughter DNA would become shorter than the parental DNA, and eventually entire DNA would be lost.

Why do chromosomes get progressively shorter after each round of DNA replication?

Your DNA strands become slightly shorter each time a chromosome replicates itself. Telomeres help prevent genes from being lost in this process. But this means that as your chromosomes replicate, your telomeres shorten. That’s where an enzyme called telomerase comes in.

Why is it necessary for telomerase to extend the end of chromosomes?

Telomerase, an enzyme with a built-in RNA template, extends the ends by copying the RNA template and extending one end of the chromosome. … In this way, the ends of the chromosomes are protected. This is important as evidence indicates telomere length may play a role in regulating cell division and the process of aging.

How does telomere shortening occur?


This telomere shortening results from a combination of a failure to completely replicate the ends of linear DNA molecules, termed the “end replication problem,” and the processing of DNA that occurs on the ends of linear chromosomes.

Why does the end replication paradox occur?

As we all know, with a linear chromosome, on the lagging strand (template 5′->3′) of DNA replication, when the last piece of RNA primer at the 3′ end is removed, the DNA cannot be extended and this creates the end replication problem.

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How are telomeres at the ends of eukaryotic chromosomes replicated quizlet?

Outline in words and pictures how telomeres at the ends of eukaryotic chromosomes are replicated. Telomeres are replicated by the enzyme telomerase. Telomerase, a ribonucleoprotein, consists of protein and an RNA molecule that is complementary to the 3′ end of the DNA of a eukaryotic chromosome.

What causes telomeres to lengthen?

A small pilot study shows for the first time that changes in diet, exercise, stress management and social support may result in longer telomeres, the parts of chromosomes that affect aging. It is the first controlled trial to show that any intervention might lengthen telomeres over time.

Which of the cells will display telomeres that progressively shorten as cells continue to divide?

Which cell displays telomeres that progressively shorten as cells continue to divide? Skin cells.

How is the end replication problem solved?

Eukaryotes have solved the end-replication problem by locating highly repeated DNA sequence at the end, or telomeres, of each linear chromosome. … In prokaryotes, the end-replication problem is solved by having circular DNA molecules as chromosomes. Another cause of telomere shortening is oxidative stress.

Why are there leading and lagging strands in DNA replication?

On the lagging strand, the DNA plymerase moves the opposite direction as helicase, thus it can only copy a small length of DNA at one time. Because of the different directions the two enzymes moves on the lagging strand, the DNA chain is only synthetised in small fragments. Hence it is called the lagging strand.

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Why does the lagging strand lag behind the leading strand?

The lagging strand is called the lagging strand because there is a substantial delay in the replication of that strand relative to the leading strand. … This delay occurs because DNA polymerization on the lagging strand is forced to occur in the direction going away from the replication fork.

Is it true that two daughter strands are completely new?

DNA replication of one helix of DNA results in two identical helices. If the original DNA helix is called the “parental” DNA, the two resulting helices can be called “daughter” helices. Each of these two daughter helices is a nearly exact copy of the parental helix (it is not 100% the same due to mutations).