DNA Replication Termination

Question 0

Eukaryotic DNA replication end w ______________ which is a ________________________.

The ends of linear chromosomes have _____________ which are capped w ______________.

Answer 0

Telomerase, ribonucleic protein

Telomeres(telomeric repeats), telomere DNA binding proteins (protect from ds break repair machinery)

Question 1

Prokaryotic DNA rep ends with

Answer 1

Topoisomerase II unlinking the catenated circular strands of DNA by releasing supercoils

Question 2

Telomeres play a role in

Answer 2

Aging (telomeres get shorter with each cell division)

Cancer (long telomeres for a high amount of DNA replication)

Balance/ paradox: fountain of youth vs cancer

Question 3

What organism was used for experimental study of telomerase and why?

Answer 3

Tetrahymena

It has 2 types of nuclei:
1. Micronuclei- germ line/ passing on genetic info

2. Macronuclei - with minichromosomes (DNA fragments) used for gene expression
   DNA fragments have 10x as many telomeres as human cell, so can isolate telomerase activity

Question 4

2 conditions=> discover telomerase has 2 components

Answer 4

1. High salt = denatured protein therefore telomerase has protein
2. RNase A = telomerase has RNA

Question 5

6 bp tetrahymena repeat

Answer 5

TTGGG

Question 6

Mechanism of telomerase

Answer 6

1. RNA template (9bps) base pairs with 3 complementary bases of 3’ overhang of template DNA
2. dTTP and dGTP 6 incorporated onto template DNA using telomerase RNA template
3. Enzyme translocation, repeat
4. Primase, DNA polymerase and ligase fills in and repairs new strand
5. Telomere DNA binding protein binds 3’ overhang to protect it from dsDNA break repair machinery