21. (11 PTS) You are working with pure-breeding strains of corn and perform the

Question

21. (11 PTS) You are working with pure-breeding strains of corn and perform the following cross Tall, Yellow kernels, Single stalks x Dwarf, Red kernels, Branched stalks All the Fl progeny are Tall, Red and Branched. Use H and h to denote the alleles of the gene that controls plant height; R and r to denote the alleles of the gene that controls kernel color; and B and b to denote the alleles of the gene that controls the shape of the stalks. In each case, the uppercase letter represents the dominant allele. (i) Write the genotypes, as they would appear on separate homologous chromosomes, of the Fl progeny You testcross the F1 progeny with a fully homozygous recessive plant and find the following offspring Phenoty Tall Yellow Single Dwarf Red Branched Tall Yellow Branched Dwarf Red Single Tall Red Branched Dwarf Yellow Single Tall Red Single Dwarf Yellow Branched TOTAL 192 58 94 96 154 156 1000 (ii) What is the map distance between the loci height (H) and stalk shape (B)? Show your work. (iii) What is the map distance between the loci kernel color (R) and stalk shape (B)? Show your (iv) What is the map distance between the loci height (H) and kernel color (R)? Show your work. (v) Draw the genetic map of these three loci, showing distances between the loci. (vi) If you perform chi-square tests to test for independent assortment, for which pair(s) of loci will you fail to reject the null hypothesis? Circle all that apply. (Hint: what does 50% recombination frequency suggest?) Height and Kernel color Kernel color and stalk shape Height and stalk shape

Explanation / Answer

Genotype of F1 progeny = Hrb/hRB

Map distance between H and B = (94+96+58+62)/1000 *100 = 31cM

Map distance between B and R = (154+156+58+62)/1000 *100 = 43cM

Genetic map = H--------31cM-------b-------42cM---------r

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