Cell Cycle

Question 1

What DNA repair occurs in G1? What disease does this fail in?

Answer 1

Nucleotide excision repair (endonucleases remove whole nucleotides then replace w/ DNA polymerase and ligase)

Xeroderma pigmentosum

Question 2

What DNA repair occurs in G2? What disease does this fail in?

Answer 2

Mismatch repair (recognize mismatched nucleotides in new strand and replace)

Lynch Syndrome (HNPCC)

Question 3

Where do p53 and Rb work?

Answer 3

B/n G1 and S

p53 –> p21 –> inhibits cyclin-dep kinases –> hypophosphorylation of Rb activates it –> inhibit G1-S progression

Question 4

Permanent Cells

Answer 4

Neurons, skeletal and cardiac muscle, RBCs

Always in G0, regenerate from stem cells

Question 5

Stable Cells

Answer 5

Enter G1 from G0 when stimulated

Hepatocytes and lymphocytes

Question 6

Labile Cells

Answer 6

Never go to G0, divide rapidly, most affected by chemo

Bone marrow, gut epithelium, skin, hair follicles, germ cells