There are many differences between the nematode C. elegans and a human, many of which a third grader would easily be able to point out. However, through the course so far I have learned of a novel difference between the two organisms: their patterns of development. C. elegans follows a pattern of development known as regulative development, while humans undergo mosaic development. In regulative development, determination of cell fate occurs extremely early in the developmental process, and cells generally are committed to a lineage . The cells’ potency diminishes by half with each cell division. However, in mosaic development determination happens much later, and is much more subject to the surrounding environment.

I had not been aware of these two divergent methods of development prior to taking this course. All of my previous developmental biology coursework was mainly focused on mammalian development, typically either mouse or human development. Any comparisons made to other organisms were very cursory, and did not explain why organisms like C. elegans make such good model organisms. However, this definition of regulative development fits in well with my knowledge of mammalian development – the determination and specification of cells within human cell lineages are highly influenced by the environment, especially through concentration gradients of morphogens like the BMP family, Shh, and Nodal.

In regards to regulative development, I had known previously that there had been a study surrounding developmental biology in which biologists believed that the zygote cytoplasm contained “determinants” that segregated to different daughter cells upon cleavage. While this was not true for humans, it was interesting to learn that this is, in fact, the case in C. elegans and other organisms. This helps me understand why C. elegans are so critical in the study of developmental biology, as each cell’s fate is known early on, and a single cell can easily be traced throughout its entire development.