Question

Wo fruit flies that are heterozygous for body color and eye color are crossed. Brown body color is dominant to black body color. Red eye color is dominant to brown eye color.
Use the Punnett square to determine the ratio of offspring with:
Brown body and red eyes
:

Brown body and brown eyes
:

Black body and red eyes
:

Black body and brown eyes
:
Punnett square

Answer 1

The crossed flies are heterozygous so they have one allele of each for the characteristics. So the genotype is Bb for body color and Rr for eye color. To set up the punnett square, you would determine all possible combinations for the alleles that each parent could provide: BR, Br, bR, and br. Then make the table, and combining the rows and columns:
    BR Br bR br
 BR BBRR BBRr BbRR BbRr
 Br BBRr BBrr BbRr Bbrr
 bR BbRR BbRr bbRR bbRr
 br BbRr Bbrr bbRr bbrr
   There are sixteen combinations of the genotypes and they need to be classified: BB or Bb- Brown body; bb- black body; RR or Rr- red eyes; rr- brown eyes
   Brown body and red eyes- 9
 Brown body and brown eyes- 3
 Black body and red eyes- 3
 Black body and brown eyes 1