The end problem in eukaryotic DNA replicationa. is solved by t.pdf

The \"end problem\" in eukaryotic DNA replication
a. is solved by telomerase
b. refers to loss of chromosome ends during replication
c. is solved by an RNA dependent DNA polymerase
d. A and B
e. all of the above
Solution
Answer : The correct answer is E ( All of the above)
Explanation :
Telomerases are the ribonucleoprotein complexes containing a small RNA that serves as a
template for addition of new six nucleotide repeats. Or Telomerase, the enzyme that synthesizes
the telomere ends of linear chromosomes, is a specialized reverse transcriptase that contains an
internal RNA template. Telomeres undergo cycles of shortening of the lagging strands due to the
inability to complete synthesis.
Most normal cells lose telomerase activity with increaseing age of the organism and repeated
generations of the cell division. In other words, after certain number of divisions normal cells
reaches the Hayflicks limit beyond which cells will no longer devide instead they die.
In germ-line cells, which contain telomerase activity, telomere lengths are maintained; for
example, telomerase is highly expressed only in cells that need to divide regularly especially in
male sperm cells. Whereas somatic cells lack telomerase activity due to which they die after
certain number of generations.
In cancer cells/tumor cells, end replication problems observed in normal cells will be taken care
by the telomerase enzyme which makes the cells to bypass the Hayflick limit and become
immortal, thus avoiding cell death Many cancer cells are considered \'immortal\' because
telomerase activity supports them to live longer than somatic cells. 90% of the cancer cells retain
the ability to express telomerase and acquires the ability to proloferate indefinitely..

1. The \"end problem\" in eukaryotic DNA replication
a. is solved by telomerase
b. refers to loss of chromosome ends during replication
c. is solved by an RNA dependent DNA polymerase
d. A and B
e. all of the above

Solution

Answer : The correct answer is E ( All of the above)
Explanation :
Telomerases are the ribonucleoprotein complexes containing a small RNA that serves as a
template for addition of new six nucleotide repeats. Or Telomerase, the enzyme that synthesizes
the telomere ends of linear chromosomes, is a specialized reverse transcriptase that contains an
internal RNA template. Telomeres undergo cycles of shortening of the lagging strands due to the
inability to complete synthesis.
Most normal cells lose telomerase activity with increaseing age of the organism and repeated
generations of the cell division. In other words, after certain number of divisions normal cells
reaches the Hayflicks limit beyond which cells will no longer devide instead they die.
In germ-line cells, which contain telomerase activity, telomere lengths are maintained; for
example, telomerase is highly expressed only in cells that need to divide regularly especially in
male sperm cells. Whereas somatic cells lack telomerase activity due to which they die after
certain number of generations.
In cancer cells/tumor cells, end replication problems observed in normal cells will be taken care
by the telomerase enzyme which makes the cells to bypass the Hayflick limit and become
immortal, thus avoiding cell death Many cancer cells are considered \'immortal\' because
telomerase activity supports them to live longer than somatic cells. 90% of the cancer cells retain
the ability to express telomerase and acquires the ability to proloferate indefinitely.