Question

R = Dominant red flowers r = Recessive white flowers As part of the class's unit on genetics, Mr. Franks' 8th period science class decided to cross two plants. Each of the parent plants had red flowers and the genotype Rr. If the plants produce 100 offspring, about how many of the plants will have red flowers? A. 25 B. 100 C. 75 D. 50

Answer 1

If we draw up a Punnett square, we will see that after crossing two heterozygous individuals the possible offspring are RR, Rr, Rr and rr:

R r

R RR Rr

r Rr rr

Now to produce red flowers, an individual must be either homozygous dominant (RR) or heterozygous (Rr) and so from the Punnett square we can see that 3/4 of the offspring would produce red flowers. If we apply this ratio to 100 offspring, then we get:
3/4*100 = 75 offspring with red flowers, thus the answer is C