Chapter 19, Problem 19P

The following figure shows the temperature-shift analysis of C. elegans embryos from mothers homozygous for a temperature-sensitive allele of the zyg-9 gene, which helps determine the polarity of the early embryo. Each dot represents an individual embryo subjected to a short (5-minute) pulse of high temperature. Green dots indicate that the embryo ultimately survives and becomes a normal worm, whereas red dots represent animals with abnormal polarity that ultimately die.

 

a.	At what time after fertilization is the zyg-9 gene required for normal development of C. elegans?
b.	The same results were obtained whether the sperm used in the fertilization had wild-type or mutant alleles of zyg-9. What does this fact say about the source of the Zyg-9 protein that is present during the narrow window of time when it is required?