Question

In fruit flies, the gene for red eyes (R) is dominant and the gene for sepia eyes (r) is recessive. What are the possible combinations of genes in the offspring of two red-eyed heterozygous flies (Rr)?

Answer 1

The possible combinations are as follows 
          
      R      r
R   RR   Rr
r     Rr    rr

so you would have a ratio of   1RR : 2Rr : 1rr