Extensions of Basic Principles Group Problems (2)

Extensions of Mendelian Genetics Group Problems (15 pts) 1. In pigeons, the major color locus ( B ) is a Z-linked gene with three alleles in the order of dominance: ash-red > blue > brown ( B A > B + > b ). There is a second locus called recessive red which is epistatic to the major locus, so that birds that are ee have the recessive red phenotype regardless of the B genotype, but birds that have at least one E will show the phenotype encoded by B. a. Predict the outcome of a cross between a blue female EE, Z( B + )W and a brown male EE, Z( b ) Z( b ), including colors and sexes of the offspring. Draw a Punnett square or branch diagram to help you. (1 pt) ½ Blue Male Z B+ Z b ½ Brown Female Z b W b. Imagine a cross between a blue female EE , Z( B + ) W and a male that has the ash-red phenotype, but is a carrier of the brown allele EE, Z( B A )Z(b). What would the sexes, phenotypes, and genotypes of their progeny be? (1 pt) ¼ Ash Red Male ¼ Blue Male ¼ Ash Red Female ¼ Brown Female c. Imagine a cross between an ash-red female EE, Z(B A )W , and a recessive red male that is homozygous for the blue allele , ee, Z(B + )Z(B + ) . What would the phenotypes of the F1 and F2 progeny be (include color and sex)? (Punnett square or branch diagram can be helpful…). Remember Mendel’s laws! (3 pt) F1: ½ Blue Females Ee, ZBW , ½ Ash-red Males Ee, Z(B + ) Z(B A ) F2: 2/16 Male Recessive Red, 2/16 Female Recessive Red, 3/16 Ash-red Male, 3/16 Blue Male, 3/16 Ash-red Female, 3/16 Blue Female,

2. In chickens, rrpp gives birds a single comb, R_P_ gives a walnut comb, rrP_ gives a pea comb, and R_pp gives a rose comb. a. What comb types will appear in the F1 and F2, and in what proportions, if a single-comb bird (rrpp) is crossed to a true-breeding walnut-comb bird (RRPP)? (2 pt) F1: 100% RrPp F2: 9/16 Walnut: 3/16 Rose: 3/16 Pea :1/16 Single b. What are the genotypes of the parents in a walnut x rose mating from which the progeny are 3/8 rose, 3/8 walnut, 1/8 pea and 1/8 single? (2 pt) Walnut: RrPp Rose: Rrpp c. Based on these data, do the R and P genes interact genetically (show epistasis)? Why or why not? (1 pt) It does not show epistasis neither blocks the expression of the other 3. In the Blue-eyed Mary, two genes (W and P) control pigment production. ww shows recessive epistasis over P, meaning that all ww plants are white regardless of their genotype at P. If at least 1 W allele is present, the dominant P allele leads to the production of blue pigment, while the recessive p allele leads to the production of pink. a. What phenotypes will appear in the F1 and the F2, and in what proportions if a pink (WWpp) plant is crossed to a white one (wwPP) (2pt). F1: WwPp F2: 9 Blue: 4 White : 3 Pink b. Draw a possible pigment synthesis pathway that would be explained by these genetic data. Show where gene W and P are acting in the pathway. (1 pt) W_->P_->pp white *block* pink *block* blue