In radishes, red and white are the pure-breeding colors and long and round are the pure-breeding shapes,?

Question

while the hybrids are purple and oval. The cross of a white oval and a purple oval will produce more:

a) red long than white long

b) purple round than white long

c) purple oval than purple long

d) purple long than purple round

e) purple round than white oval

Answer 1

You can figure this out using a Punnett square.  

What's important to recognize here are that red, white, long, and round are the homozygous genotypes so if you use R for red (r could be white) RR is red, rr is white, and Rr is purple.  For shapes, L can be long, l can be round, so Ll is the genotype for oval.  When you say a trait is pure-breeding, that should tell you that both alleles (genes for that trait) are the same - when crossed, they can't produce anything else.

So if you cross a white oval (rrLl) with a purple oval (RrLl) use the FOIL principle (the First set of letters, the Outside set, the Inside set, and the Last set) to find the possible combinations of alleles produced.

For the white oval, you'd have rL, rl, rL, and rl

For the purple oval, you'd have RL, Rl, rL, and rl.

Now set up your square:

___|_rL_|_rl_|_rL_|_rl_|

RL_|___|___|___|___|

Rl_|___|___|___|___|

rL_|___|___|___|___|

rl_|___|___|___|___|

Now, all you have to do is to combine the letters from the top and side for each of the 16 (the first box would be RrLL, or purple long), and figure out the phenotype for each.  Just tally what each looks like, and see which you get more of.