Each worm develops the same way , with a series of cell divisions that always give rise to the same daughter cells. Scientists have constructed a huge cell lineage map of all the somatic cells of the worm, and this has led to the identification of interesting developmental mutants. The second is that even cell death is programmed into development 4. However, the most interesting info comes from looking at mutations that change this developmental program. V5 includes a programmed cell death and terminal differentiations not normally seen in V1-V4, so the result is many fewer cells, and not the right ones.
Mutations can also change the timing of certain events .
Despite the cell lineage map, communication among cells is also important in worm development. The vulva is the opening that allows the eggs to come out after fertilization, so its development needs to be coordinated with gonad development. So normally the other 3 cells don t get the initial signal. But there is a further complication - the middle cell makes a different part of the vulva than the flanking cells on either side. By making lots of mutations in genes, and checking the vulval phenotype , the worm scientists were able to find a mutation in which all 3 hypodermal cells made the same middle part of the vulva.