Practice Problem 122 Programmed cell death, also called apoptosis, is a genetica

Question

Practice Problem 122

Programmed cell death, also called apoptosis, is a genetically controlled event that helps shape organs and tissues during normal development. In the nematode C. elegans, normal development relies on three genes involved in programmed cell death, ced-3, ced-4, and ced-9.

Part A

In C. elegans,ced-3 and ced-4 initiate the genetic events that lead to programmed cell death (apoptosis). The expression of ced-3 and ced-4 are controlled by ced-9.

The ced-9 gene acts as a "binary switch" in the genetic pathway controlling cell death, as shown in the diagram.

If ced-9 is active, ced-3 and ced-4 are repressed, allowing the cell to remain alive (and not undergo programmed cell death).

However, if ced-9 is inactive, ced-3 and ced-4 are expressed and initiate cell death.

For each mutation described below, determine whether it would result in cell survival or cell death.

Drag the terms to the appropriate blanks to complete the sentences. Terms can be used once, more than once, or not at all.

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result in cell survival

result in cell death

have no effect on cell survival or cell death

1. A gain-of-function mutation in ced-9 would result in cell survival.

2. A loss-of-function mutation in ced-9 would result in cell death.

3. A gain-of-function mutation in ced-3 and a loss-of-function mutation in ced-9 would result in cell death. Correct

4. A loss-of-function mutation in ced-4 and a gain-of-function mutation in ced-9 would result in cell survival. Correct

5. A gain-of-function mutation in ced-3 and a gain-of-function mutation in ced-9 would have no effect on cell survival or cell death.

6. A loss-of-function mutation in ced-4 and a loss-of-function mutation in ced-9 would result in cell death. Correct

One of the six is incorrect.

Help

Reset

result in cell survival

result in cell death

have no effect on cell survival or cell death

1. A gain-of-function mutation in ced-9 would result in cell survival.

2. A loss-of-function mutation in ced-9 would result in cell death.

3. A gain-of-function mutation in ced-3 and a loss-of-function mutation in ced-9 would result in cell death. Correct

4. A loss-of-function mutation in ced-4 and a gain-of-function mutation in ced-9 would result in cell survival. Correct

5. A gain-of-function mutation in ced-3 and a gain-of-function mutation in ced-9 would have no effect on cell survival or cell death.

6. A loss-of-function mutation in ced-4 and a loss-of-function mutation in ced-9 would result in cell death. Correct

One of the six is incorrect.

Explanation / Answer

OUT OF THE SIX RESULTS A THAT IS A GAIN OF FUNCTION IN CED-9 WOULD RESULT IN CELL SURVIVAL IS INCORRECT. CED 9 IS A NEGATIVE REGULATOR OF CELL DEATH OR APOPTOSIS. THE OVEREXPRESSION OF THE CED 9 REULTS IN SURVIVAL RATHER THAN CELL DEATH. THE GAIN OF FUNCTION LEAD TO DISTORTION OF OPEN READING FRAME. CED 9 ACT AS A SUPRESSOR OF PROGRAMED CELL DEATH WHICH IS NECESSARY TO STOP THE SUICIDAL ATTEMPT OF THE CELL. CED 9 MUTANT INHIBITS THE CED 3 MUTANT.

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