Hello people in net,
I am an undergraduate biology student. I have some difficulty
in predicting the result of a D. melanogaster cross-test between male
wild type and female hybrid y cv v f /+ + + +. Theoretically, there
should be 2 high 4 equal 16 possible Genotypes under the sons. To
calculate their frequency, I need 16 equations. What a pity, I can
only find 15 equations at all:
a. The sum of all 16 parts is 100%. (1 equation)
b. Because of the reciprocal character of normal cross-over, 8 parts
are numerically equal to their corresponding 8 parts, for example the
frequency of y cv v + /- - - - ist equal the frequency of + + + f/- -
- - , ... (8 equations)
c. calculation of recombination between two allel pairs from four pairs
(2)
(4)=4x3/2=6 equations
--------------------------------------------------
you see that there are only 15 equations here. There is no problem in
prediction in case of 2 or 3 allel pairs using the same method, the (perhaps mathematic)
probblem begins to disturb up 4 pairs.
Thanks in advance
Linyi Wang
e-mail: 1wang at rzdspc5.informatik.uni-hamburg.de