Telomeres /telomerases Flashcards
1
Q
What are telomeres ?
A
Repetitive regions at the very ends of chromosomes.
- they act as caps that protect internal regions of the chromosomes
- they are worm down a small amount in each round of DNA replication
2
Q
Why are telomeres important ?
A
They prevent the loss of genes as chromosome ends are worn down as they are found at the at ends of DNA.
3
Q
What is the role of telomerase ?
A
- telomerase enzyme has the ability to reverse the shortening of telomeres of chromosomes.
- it is a RNA dependant DNA polymerase , meaning it is an enzyme that can make DNA using RNA as a template.
4
Q
How does telomerase prevent the shortening of telomeres ?
A
- telomerase binds to a special RNA molecule that contains a sequence complementary to the telomeric repeat at the 3’ end .
- it adds adds nucleotides to the overhanging strand of the telomere DNA using this complementary RNA as a template.
- RNA template shifts along the 3’ end of the telomere and the process of adding complementary bases continues along the 3’ end.
- when the overhang is long enough , a matching strand can be made by normal DNA replication At the 5’ end.
5
Q
How can interfering with telomerase activity allow treatment of cancer ?
A
- many cancer cells have shortened telomeres.
- and telomerase is active in these cancer cells.
- if telomerase could be inhibited by drugs during cancer therapy , their excess division of DNA could potentially be stopped as it prevents telomeres from extending.
6
Q
Why as we grow up , why do we age ?
A
- as we grow up , telomerase gradually becomes inactive. So , eventually generation after generation chromosomes shorten. Whereas in cancer cells , telomerase is ALWAYS active which causes cancer cells to continuously divide and never die.
7
Q
Why isn’t all DNAusually copied during DNA replication?
A
- the lagging strand is too short - the DNA primer would go beyond the length of the lagging strand so the lagging strand needs to be extended - this occurs with the help of telomerase.
