In the summer squash, fruits may be white, yellow, or green. In one case, the cross of yellow X white produced an F1 of all white-fruited plants that, when selfed, gave an F2 segregating 12 white: 3 yellow: 1 green. (a) suggest gnotypes for the white, yellow, and green phenotypes. (b) give genotypes of the P, F1, and F2 of this cross.

Question

In the summer squash, fruits may be white, yellow, or green.  In one case, the cross of yellow X white produced an F1 of all white-fruited plants that, when selfed, gave an F2 segregating 12 white: 3 yellow: 1 green.  (a) suggest gnotypes for the white, yellow, and green phenotypes.  (b) give genotypes of the P, F1, and F2 of this cross.

Happy · Accepted Answer

can you explain step by step how you got these answers? I have tried many ways and I'm still not understanding it.

bobpursley · Answer

P: Yg x WW yellow x white
F1: YW,YW, gW, gW all white
F2:
first two YY,YW,WW,YW one Yel, 3W
first, third Yg,YW,Wg,WW one Yel, 3W
first, fourth Yg,YW,Wg,WW one Yel, 3W
second third Yg,YW,Wg,WW one Yel, 3 W
third, fourth gg,gW, Wg, WW one g, 3W
now if W dominates to y,g, and Y dominates to g, then I count 15/20 W, 1/20 g, and 3/20 yellow
Now in the F2 above, there were 12/16 W,3/16 Yellow, and 1/16 green Those frequencies look very close to what I laid out.
White 12
Yellow 4
green