Dallas County Community College

• BIO 102

Lab 2 HW Assignment 1) Dihybrid cross with dominance – In lab, we used this notation: W for normal wings, w for vestigial wings, B for light body, b for ebony body a) What is the phenotype of the F1 flies? What does this tell you about the dominance versus recessive nature of the mutations? Ans: P: WWBB x wwbb F1: WwBb (Normal wings and light body color) The phenotype of the F1 flies is normal wings with light bodies. This tells us that the normal wings and light bodies have the dominance nature whereas the vestigial wings and ebony bodies have recessive nature of the mutations. b) What is the experimental hypothesis being tested here? Ans: The experimental hypothesis being tested here is that the offspring of the F2 generation will have unlinked genes with a genotypic ratio of 9:3:3:1 for the wings and body color. c) Define the H0 (null hypothesis) and a possible HA (alternative hypothesis): Ans: H0 (null hypothesis): The genes are unlinked and has 9:3:3:1 as genotypic ratio. HA (alternative hypothesis): The genes are linked and does not have 9:3:3:1 as genotypic ratio. d) Chi 2 calculations Phenotype Expected Ratio Expected Counts (Ei) Observed Counts (Oi) Deviation (di) = (Ei – Oi) di 2 = (Ei – Oi) 2 di 2 /Ei WW BB 9 544