DNA replication and repair; repair disorders, repeat disorders

Question 1

What are telomeres?

Answer 1

Telomeres are noncoding stretches of repeat sequences at the end of a chromosome.

Question 2

What is the purpose of telomeres?

Answer 2

1. Protect the end of a chromosome from being recognized as DNA damage (double strand break) and being “repaired.”
2. Allow for some bases to get lost during the natural process of replication.
3. Mechanism for limiting cell life span. When telomeres get too short, apoptosis is initiated.

Question 3

What does telomerase do?

Answer 3

Telomerase builds telomeres. It is usually only functional in fetal cells and adult germ cells. Once a cell has differentiated, it’s telomerase is turned off and telomeres become shorter, limiting lifespan.

Question 4

What is the role of telomerase in cancer?

Answer 4

Cancerous cells turn their telomerase back on, allowing them to rebuild their telomeres and become immortal.