How does X inactivation contribute to a person’s phenotype? a. It controls the number and kind of genes inherited on an X chromosome. b. It determines which X chromosome is expressed in a male. c. It allows for the expression of either the maternal or the paternal X in different cells. d. It enhances the expression of Y-linked genes in males.

You examine a maternal effect protein that regulates cell division. Will a mutation in this gene display a defect in the mother with the mutation, or in her offspring who have not inherited the mutation?

There is a protein called neurogenin that stimulates neuronal cells to differentiate. In order to determine what kind of receptor neurogenin binds to, you add a general phosphatase (one that can remove phosphates from any substrate) to neural cells when you add neurogenin, and you discover that this inhibits differentiation. Furthermore, in the presence of this phosphatase, you find that not even a G protein is activated in response to neurogenin. 1.  With this information, what kind of receptor does neurogenin bind to? 2.  In a normal cell, how does the G protein in this pathway get activated? 3.  In a normal cell, why does the response to neurogenin cease over time?

What are X-inactivation and Barr body?