Yeast Genetics Discussion PP

Haploids HB1, HA1, and HA2 could not grow on their own as they could not synthesize their own adenine. This makes sense because they all had an ade mutation that makes them mutant deficient for adenine biosynthesis. Haploid HA0 could grow on its own, meaning that it can synthesize its own adenine. Again, this makes sense because this haploid strain had no mutations in any of its ade genes. The cross between HB1xHA1 did not proliferate. Because the cross contained one MATa and one MATα, sexual reproduction is possible. However, because it did not proliferate, it means that their alleles are not complementary. Next, the cross of HA1xHA2 did not proliferate. In this cross, both the haploids were MATa, therefore sexual reproduction is not possible and no proliferation is expected. The cross HB1xHA2 did proliferate. Both of these haploids could not grow on their own, however, when they were crossed they were able to proliferate. This cross contains one MATα and one MATa, thus the proliferation is caused by the complementation of their alleles. Finally, the cross of HB1xHA0 was able to proliferate. This cross needs to be furthered examined because although HB1 is MATα and HA0 is MATa, one cannot assume they sexually reproduced. As we know, HA0 is able to proliferate on its own, so either their alleles are complementary and it proliferated or it’s just HA0 proliferating and HB1 dying off.