Campbell Problem 7

Molecular Genetics Problem 7
7. Using the information from problem 6, a further testcross was done using a heterozygote for height and nose morphology. The offspring were tall-upturned nose, 40; dwarf-upturned nose, 9; dwarf-downturned nose, 42; tall-downturned nose, 9. Calculate the recombination frequency from these data; then use your answer from problem 6 to determine the correct sequence of the three linked genes.

Experiment 3. (Frequency/Distance between T and S)

Determine the recombination frequency for the genes controlling Tallness and Snout:

40 tall-upturned snout = 40%expected
42 dwarf-downturned snout= 42%expected
9 dwarf-upturned snout= 9%recombinant
9 tall-downturned snout= 9%recombinant

Total = 100%

Therefore this recombination frequency between genes T and S is 18%

One can determine the relative frequency between genes using the percent frequencies as distances.

The Recombinant relationships from experiments 1-3 are:

Exp. 1 T-A = 12 map units Exp. 2 A-S = 5 map units Exp. 3 T-S = 18 map units

An arrangement that fits the data would be: