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: