Unformatted text preview: broad leaves. 6-7% is just about 1/16 of the total F2 offspring, which would indicate that these are the “1” in the classic 9:3:3:1 ratio we expect from a dihybrid cross in which each of the two genes is responsible for one of the traits, each gene has two alleles, simple dominance and recessiveness holds, and we have both parents (the F1 in this case) being heterozygous for both genes (like the pea color/shape cross we went over in class). This then suggests that the red/broad offspring are double recessive for each gene (let’s denote that as rrbb). Then we can conclude that the R allele gives blue color and is dominant over the r allele, while the B allele gives narrow leaves and is dominant over the b allele. Since we know that both original parents were homozygous, we can conclude that the blue/broad parent was RRbb and the red/narrow parent was rrBB. Thus, all the F1 would have been RrBb, and this explains the result noted for the F2 generation....
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- Spring '06
- red ﬂowers, narrow leaves, broad leaves