Unformatted text preview: of the 1 activator and the 2
repressor accounts for both and a cell types. By
contrast, the a1 protein expressed in a-type cells performs no function necessary for mating or differentiation into a cells. The interaction between a1
and 2 coregulators makes MATa/ MAT heterozygous diploids sterile.
5. Heterothallic yeast strains are unable to switch mating type, while homothallic yeast strains can switch
from a to and back again. Mating type switching in
homothallic strains is controlled by the activity of the
MAT locus, the HO gene, the alleles at HML and
HMR, and the four SIR genes. Two general rules govern HO-mediated switching: (1) Cells always switch
in pairs, and (2) cells must gain competence to switch
by undergoing at least one cell division.
6. a and cells communicate through pheromones determined by a-speciﬁc and -speciﬁc genes. a cells secrete a pheromone, while cells secrete pheromone.
Each cell type carries receptors for the opposite type
pheromone. The binding of pheromone from the
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This note was uploaded on 10/03/2013 for the course BI 206 taught by Professor Celenza during the Spring '08 term at BU.
- Spring '08