Telomeres, Cell Aging and Senescence

Question 1

end replication problem

Answer 1

5’ end of each newly-synthesized lagging strand cannot be completed
results in shorter and shorter dna strands which can eventually cut into genes

Question 2

Telomerase

Answer 2

the enzyme able to both maintain and extend the length of telomeres.
Protein + RNA

Question 3

protein (TERT) and RNA (TERC) subunits

Answer 3

catalyzes the addition of telomeric repeats at the telomere

Question 4

Telomerase enzyme includes the RNA
template for the

Answer 4

species of its origin

Question 5

Telomerase is strongly expressed only in a limited
number of cells

Answer 5

stems cells, germline, cancer

Question 6

Cyclins

Answer 6

promote progression through the cell cycle
- partner with CDK

Question 7

P21

Answer 7

inhibitor of a cyclin/CDK complex that turns off cell cycle

Question 8

p53

Answer 8

a tumor suppressor gene (delete = get a tumor)

Question 9

p21 inhibitor is expressed

Answer 9

in senescent cells

Question 10

Hayflick limit

Answer 10

cells have a limited ability to divide

Question 11

Werner syndrome/fibroblasts

Answer 11

Fibroblasts Divide Fewer Times

Question 12

Mitotic Clock Theory

Answer 12

old cells “sense” short telomeres and induce cell cycle arrest

Question 13

How do shortened telomeres cause somatic cell senescence?

Answer 13

TF p53 is phosphorylated upon stress
-p21 is transcribed
p21 inhibits cyclin/Cdk to arrest cells

Question 14

supporting mitotic clock theory

Answer 14

Adding telomerase gene hTRT diminishes senescence reporter b-galactosidase
- changes hayflick limit
- Mice manipulated to have extra long telomeres live longer

Question 15

dyskeratosis congenita

Answer 15

Defects in telomerase, TERT, or telomerase RNA component, TERC