REPLICATION 1 Telomerase an enzyme with both RNA a protein c

REPLICATION

1. Telomerase, an enzyme with both RNA a protein components, lengthens the telomeres at the end of eukaryotic chromosomes.

a. (1 PT) What is the biological role of telomeres?

b. (2 PTS) Why is there a need for a special enzyme to assist with the replication of chromosome ends?

c. (1 PT) Does the telomerase enzyme use an RNA or DNA template when it adds the nucleotides to a DNA strand?

d. (1 PT) Does telomerase add ribonucleotides or deoxyribonucleotides?

e. (1 PT) Does the telomerase enzyme add nucleotides to the under-hang or the overhang of the chromosome ends?

f. (1 PT) Which enzyme completes the extension of the 5’ end of the DNA molecule? g. (2 PTS) What is the effect of cancer on telomere length?

Solution

a. ANS: TELOMERASE a reverse transcriptase that RNA dependent DNA polymerase prevent END REPLICATION problem in eukarotes replication.

b. ANS: In DNA replication terminal region of linear chromosome in eukaryotes present a specific problem called end replication problem. RNA primer at the 5\' end is removed so the gap may not filled, so the same shortage of DNA sequence repeated over and over again. It finally results in loss of genetic information. So the enzyme telomerase prevent DNA from this genetic information loss.

c. ANS: when telomerase adds nucleotides to a DNA strand, it acts like a RNA dependent DNA polymerase. Telomerase is is a complex of ribo nuclio protein made up of RNA and protein.

d. ANS: Telomerase binds to the 3\' end of DNA and then extends by it adding deoxy ribonucleotides.

e. ANS: The telomerase enzyme add nucleotides to the overhang of the chromosome ends (3\' end).

f. ANS: DNA polymerase enzyme completes the extension of the 5’ end of the DNA molecule.

g. ANS: Telomerase shortening is commonly acquired during the process of cancer development. Shortening of telomeres can reduce genomic instability and chromosome loss. Telomerases which present in cancer tumors are significantly shorter than surrounding normal tissue.