2. In corn, the alleles c+ and c result in colored versus colorless seeds, wx+ and wx
in nonwaxy versus waxy endosperm, and sh+ and sh in plump versus shrunken
endosperm. When plants grown from seeds
heterozygous for each of these pairs of alleles (from crosses of pure breeding
colorless waxy plump parents with pure breeding colored, nonwaxy, shrunken
parents) were testcrossed with plants from colorless, waxy, shrunken seeds, the
progeny seeds were as follows:
colorless, nonwaxy, shrunken 55
colorless, nonwaxy, plump 105
colorless, waxy, shrunken 5
colorless, waxy, plump 334
colored, waxy, shrunken 98
colored, waxy, plump 61
colored, nonwaxy, shrunken 339
colored, nonwaxy, plump 3
a. What is the order of the 3 genes?
b. What is the distance in map units between genes c and sh?
c. What is the distance in map units between genes wx and c?
d.What is the distance in map units between genes wx and sh?
e. Draw a map to illustrate the distances between the three loci.
f. Calculate interference.
- a. c, sh, wx
- b. 55+61+5+3 = 124/1000 x 100
- = 12.4 mu
- c. 55+61+10+6+105+98 = 335/1000 x 100
- = 33.5 mu
- d. 105+98+5+3=211/1000 x 100 = 21.1 mu
- e. c ---12.4---sh-----21.1---wx (total: 33.5)
- f. E= (0.124 x 0.211) x 1000 = 26
- C = O/E = 8/26 = 0.308
- I = 1-C = 1 – 0.308 = 0.692 or 69.2% positive interference