Final answer:
Null mutations in the ced-9 gene result in the loss of its protein's function leading to unregulated apoptosis, due to the lack of inhibition on CED-3 and CED-4 proteins.
Step-by-step explanation:
Null mutations of ced-9 lead to the activation of a cell death pathway. CED-9 is a protein in C. elegans that inhibits the activity of CED-3 and CED-4, proteins that promote apoptosis or programmed cell death. When a null mutation occurs in the ced-9 gene, it results in the loss of function of the CED-9 protein, which otherwise helps to protect cells from undergoing apoptosis. Without the inhibitory action of CED-9, CED-3 and CED-4 become active, leading to the cell's auto-destruction. Null mutations of ced-9 are notable because they elucidate the genetic pathways that regulate apoptosis, which is a crucial process for the proper development and maintenance of tissues in multicellular organisms.