In four O'clock flowers, red is incompletely dominant over white
giving you a passionate pink flower. However, a straight stem is
completely dominant over a curved stem. If a pink flower that is
heterozygous for a straight stem is corssed with a white, curved
flower, what would be the chances of geting a white straight flower?

Hi Jennifer,

This question is similar to the roan horses one from before, since it
deals with incomplete dominance.

Color: R vs. r (RR=red, Rr=pink, rr=white)
Stem: S vs. s (SS or Ss=straight, ss=curved)

Parents: RrSs and rrss

Now we do our cross:

RrSs (pink, straight) : 1
Rrss (pink, curved) : 1
rrSs (white, straight) : 1
rrss (white, curved) : 1

Remember that, since one parent is homozygous, that parent can only
give an r and an s to children.  The other parent is heterozygous for
both genes, so it can give either allele in any combination with the
other gene.  Since there are four ways to combine two items with two
variations each, there are four equally likely offspring.  So, there's
a 1/4 or 25% chance that any given "child" will be white and straight.

Librariankt