BISC 202 Lecture Notes - Lecture 22: Wild Type, Dihybrid Cross, Synthetic Lethality

• School: Simon Fraser University
• Department: Biological Sciences
• Course: BISC 202
• Professor: Michael Hart

Document Summary

Bisc202 lecture 22: modified f2 ratios from gene pair interactions (continued) Consider 2 genes that encode enzyme in the same pathway (so complementary), but the intermediate compounds are coloured so they can be observed. These are crossed together to make all blue flowers in the f1. Then, perform dihybrid cross via f1 offspring. Pathway = colourless >(w+)> pink >(m+)> blue. 9 blue : 3 pink : 4 white. 9/16 will have at least 1 wild type allele for each gene (w+/_ ; m+/_): 3/16 will be homozygous recessive for the second gene in the pathway (w+/_ ; m/m): 3/16 will be homozygous recessive for the first gene in the pathway (w/w ; m+/_): 1/16 will be homozygous recessive for both genes (w/w ; m/m): When 2 genes share a biosynthetic pathway, the earlier acting gene tends to be epistatic (doesn"t matter if later enzymes is present or not) In this case, the w gene is epistatic to the m gene.