Chap 6 - Gene interaction

Chap 6 - Gene interaction - GENETICS (BIO 325) _ Chap 6...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
GENETICS (BIO 325) ________________________________________________________________ Chap 6 (Gene Interaction) 1. Dominant epistasis (12: 3: 1) When the dominant allele at one locus, for example the A allele, produces a certain phenotype regardless of the allelic condition of the other locus, then the A-locus is said to be epistatic to the B-locus. Furthermore, since the dominant allele A is able to express itself in the presence of either B or b, this is a case of dominant epistasis. Only when the genotype of the individual is homozygous recessive at the epistatic locus (a/a) can the alleles of the hypostatic locus (B or b) be expressed. Thus the genotypes A/-; B/- and A/-; b/b produce the same phenotype, whereas a/a: B/- and a/a; b/b produce two additional phenotypes. The classical 9: 3: 3: 1 ratio becomes modified into a 12: 3: 1 ratio. 2. Recessive epistasis (9: 3: 4) If the recessive genotype at one locus (for example, a/a) suppresses the expression of alleles at the B-locus, the A-locus is said to exhibit recessive
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/03/2009 for the course BIO 325 taught by Professor Saxena during the Spring '08 term at University of Texas at Austin.

Ask a homework question - tutors are online