PLEASE DO NOT POST THE FIGURE! I HAVE SEEN IT AND I AM STILL CONFUSED Telomerase

Question

PLEASE DO NOT POST THE FIGURE! I HAVE SEEN IT AND I AM STILL CONFUSED

Telomerase helps to maintain eukaryotic chromosome end length by reverse transcribing AGGGTT repeats on the very end of the extended 5' strand. The model in your textbook (Figure 34.22, Tymoczko3e; Figure 28.31, Berg8e) shows how this is accomplished. The drawing stops short of showing how the 3' end of the lagging strand itself is restored to its appropriate length. Using your knowledge of the steps in replication and the selections below, indicate the order of steps that would accomplish this.

Step 1  

Step 2  

Step 3  

Step 4

Options for each are:

DNA Ligation

DNA Polymerization

RNA Excision

RNA Priming

Explanation / Answer

The telomerase is an enzyme that has an inbuilt RNA segment that complements the the 3' end of the DNA.

The 3' end is then extended using the inbuilt RNA ( DNA polymerization). After elongation of 3'OH, the telomerase leaves.  

Once the 3' end is elongated, the 5' end is also polymerized using 3' elongated end as a template using the DNA primase (RNA priming) and Polymerase.

After both strands have been elongated, the RNA primer used for 5' strand polymerization is excised (RNA excision)

The gap left after primer removal is ligated (DNA ligation).

Thus Step 1: DNA polymerization

Step 2: RNA priming

Step 3: RNA excision

Step 4: DNA ligation

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