Based on the programmed cell death pathway (shown in picture below), indicate th

Question

Based on the programmed cell death pathway (shown in picture below), indicate the phenotype of following (such as “cells failed to die”):

ced-9 loss-of-function mutant:

ced-3 loss-of-function:

ced-1 loss-of-function:

“ced-9; ced-3” double loss-of-function mutant:

“ced-3; ced-1” double loss-of-function mutant:

Engulfment Decision Commitment Execution of of to to die death die dead cell Genetic pathway Fate ced-1 determining or egl-1 ced-9 -H ced-4- ced-3 ced-2 genes Cells fated ced-9 ced-4 ced-3 Cell ON OFF OFF LIVES to live Cells fated ced-9 ced-4 ced-3 Cell ced-1 Dead cell OFF to die ON ON DIES ced-2 engulfed ON and digested

Explanation / Answer

The given programmed cell death pathway shows some important regulatory genes which either block or favor the process of apoptosis. Among the given genes, ced-9 is an anti-apoptotic gene. The genes which promote apoptosis are ced-4 and ced-3. The gene products of ced-1 and ced-2 favors the clearance of dead cells.

(i) ced-9 loss-of-function mutant: Programmed cell death occur. Cells fated to live also die.

(ii) ced-3 loss-of-function: No programmed cell death, i.e cells failed to die.

(iii) ced-1 loss-of-function: Cell corpses accumulate.

(iv) “ced-9; ced-3” double loss-of-function mutant: No programmed cell death, i.e cells failed to die. But in this double mutant, there be random death (no apoptosis)

(v) “ced-3; ced-1” double loss-of-function mutant: Cells fated to die will live and there will be no programmed cell death.

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