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Unformatted text preview: enotype of -pheromone degradation. The 1 and 2 Genes Are Master
What hypothesis could explain the roles of 1 and 2 in
determining cell type? According to the proposal illustrated in Fig. A.9a, MAT is a complex locus consisting of
two genes, 1 and 2. The 1 gene encodes an activator of
the -speciﬁc function required to elicit the cell type. In
the absence of a functional 1 product, cells are sterile,
in part because they do not produce -speciﬁc proteins
(a) MAT locus of α cell α1
Activator (b) MAT locus of a cell (a-specific genes)
(α-specific genes) hsg Yα asg
αsg Repressor α2 (haploid-specific genes) RME Meiosis asg
No α1 activator.
αsg not activated αsg Ya hsg a1 RME Meiosis (c) MAT loci of a / α cell
α2 asg Yα
a1, α2 corepressors αsg No α1 activator. hsg Ya
a1 Figure A.9 RME Meiosis MATa and MAT loci. Two different versions of the
MAT locus, MATa and MAT , share some common DNA sequences
(shown in pink) but also contain unique sequences known as Ya
and Y . The presence of Ya, Y , or Ya Y in a cell has different
consequences on expression of the a-speciﬁc, -speciﬁc, haploidspeciﬁc, and meiosis (RME) genes because activators and repressors
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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