Texts: 2. (Chapter 4 and Metabolic Pathways / Epistasis Screencasts) A true-breeding white-flowered plant was crossed with a true-breeding orange-flowered strain. All of the F1 progeny had red flowers. When the F1 offspring were crossed with one another, the F2 offspring yielded the following phenotype frequencies for flower color: F2: 44 Red 14 Orange 20 White Using this information, postulate the role of mutant genes and their products in producing the observed phenotypes: (a) Designate alleles and give the general genotypic formula for parental strains and give the general genotypic formula that defines each color class. I will post a different link for #2 when done. 2- Explain the phenotypic ratio obtained [say what it is] (See attached Table 1), AND finally (d) diagram/draw a metabolic pathway that explains the formation of each pigment (or lack thereof). Table 1: Summary of Epistatic F2 Phenotypic Ratios from an F1 A/a B/b X A/a B/b Cross in Which Complete Dominance is Shown for Each Allele Pair F2 Phenotypic Ratio from an A/a B/b X A/a B/b Cross A/- B/- A/- b/b a/a B/- a/a b/b 9 3 3 1 Gene Interaction None Recessive Epistasis a/a epistatic to B and b 9 3 4 Dominant Epistasis A epistatic to B and b 12 3 1 Duplicate Recessive Epistasis a/a epistatic to B and b; and b/b epistatic to A and a 6 7 15 1 Duplicate Dominant Epistasis A epistatic to B and b; and B epistatic to A and a 6 7 15 1

Views: 5,560 students