Essential Genetics 6th Edition by Daniel Hartl

تمرين 10

A genetically wildtype natural isolate of Neurospora crassa was crossed with a laboratory strain carrying a recessive allele ad5 known to be 10 map units from the centromere. The resulting asci showed only 2 percent second-division segregation, and many of the asci contained inviable ascospores. One of the ad5 - bearing ascospores from a second-division segregation ascus was germinated and mated with the original wildtype isolate. In this case, the resulting asci showed the expected 20 percent second division segregation. How can you account for these results?