1. Discuss how cellular differentiation occurs as different genes are turned on and off, and how different proteins and enzymatic products are produced in diffes kinds of cells; review the differences in various kinds of tissues and discuss how all these very dissimilar cells could come from a single zygote.
2. Discuss why the cleavage process goes through many rounds of cell division with no cell growth, starting with the egg as the largest single cell in a species. Talk about the concept that differentiation may begin with the first cell division and how that could be important.
3. Examine why you could consider the yolk of an egg to be a she cell and why that really is not a reasonable conclusion, since the majority of the yolk is simply nutrient material used as the cellular part of the yolk goes through cell division to form an embryonic plate that will develop into a chick.
4. Talk about how a chick embryo might have requirements other than the nutrients in the yolk and how they are dealt withósuch as oxygen requirements (enters the shell) and removal of wastes (accumulate as uric acid in one of the extraembryonic melnes and are discarded with the eggshell).
5. Discuss how amniotic fluid is used to examine
a fetus for genetic defects, since cells of the fetus are shed
from the skin and from the respiratory and urinary tracts into
the fluid. Also discuss how chorionic villi are now being sampled
in prenatal diagnosis.