Anonymous
06-03-2004, 08:49 PM
Problem 6: p53
ans:
A. p53 with a mutation directly stimulates the growth of cancer cells.
Incorrect.
p53 can block the cell cycle allowing DNA repair or stimulate apoptosis.
B. Mutations in p53 would prevent abnormal cells from dying by apoptosis.
Correct.
If the mechanism for eliminating abnormal cells is defective, then the cells will continue to divide and further damage their DNA. This process leads to cancer. Exposure to sun also causes apoptosis in damaged cells. This produces the familiar peeling and blistering associated with severe sunburn. Over many years, exposure to sun also leads to cancer. It is particularly interesting that smoke seems to cause a high frequency of p53 mutations.
C. Mutant p53 triggers the M phase of the cell cycle leading to abnormal cell division.
Incorrect.
p53 blocks the S phase until a cell can repair damaged DNA.
D. p53 causes a cell to enter G0, blocking cell division.
Incorrect.
p53 only blocks the cell cycle until a cell can repair its DNA. Then the cycle continues unless the damage has included production of cancer causing genes. In this case, p53 in some unknown way stimulates apoptosis.
ans:
A. p53 with a mutation directly stimulates the growth of cancer cells.
Incorrect.
p53 can block the cell cycle allowing DNA repair or stimulate apoptosis.
B. Mutations in p53 would prevent abnormal cells from dying by apoptosis.
Correct.
If the mechanism for eliminating abnormal cells is defective, then the cells will continue to divide and further damage their DNA. This process leads to cancer. Exposure to sun also causes apoptosis in damaged cells. This produces the familiar peeling and blistering associated with severe sunburn. Over many years, exposure to sun also leads to cancer. It is particularly interesting that smoke seems to cause a high frequency of p53 mutations.
C. Mutant p53 triggers the M phase of the cell cycle leading to abnormal cell division.
Incorrect.
p53 blocks the S phase until a cell can repair damaged DNA.
D. p53 causes a cell to enter G0, blocking cell division.
Incorrect.
p53 only blocks the cell cycle until a cell can repair its DNA. Then the cycle continues unless the damage has included production of cancer causing genes. In this case, p53 in some unknown way stimulates apoptosis.