Question

In fruit flies, gray body color is dominant over black body color. suppose two fruit flies heterozygous for the alleles that carry body color are crossed and 200 offspring are produced. how many would you expect to have black bodies?

Answer 1

When two heterozygous fruit flies are crossed, the expected ratio of black-bodied to gray-bodied offspring is 1:3. Since black body color is recessive, 25% of the 200 offspring, which equates to 50 flies, are expected to have black bodies.

Step-by-step explanation:

In fruit flies, gray body color is dominant over black body color. If two fruit flies that are heterozygous for the alleles that determine body color are crossed (genotype Bb), we can use a Punnett square to predict the genetic outcome of their offspring. According to Mendelian genetics, a cross between two heterozygous individuals (Bb x Bb) will result in the following genotype ratio: 1 BB : 2 Bb : 1 bb. The phenotype ratio will be 3 gray-bodied flies : 1 black-bodied fly since gray is dominant and black is recessive.

For 200 offspring, you would expect 25% to have black bodies. To determine the expected number, multiply the total number of offspring by the percentage expected to have black bodies (0.25 x 200 = 50). Therefore, it's reasonable to expect 50 black-bodied fruit flies out of 200 offspring from the cross of two heterozygous flies.

Answer 2

Seventy-five percent i.e.e, 150 flies will be having a gray body, another twenty-five will have a black body. Out seventy percent gray flies, twenty-five percent will still carry an allele for the black body. You can use Punnett square to understand the calculation.