Biology Forums - Study Force

8. In peas a gene for tall plants (T) is dominant over its allele for short plants (t). The gene for smooth peas (S) is dominant over its allele for wrinkled peas (s). Calculate both phenotypic ratios and genotypic ratios for the results of each of the following crosses:

TtSs x TtSs    Ttss x ttss     ttSs x Ttss     TTss x ttSS


9. In hogs a gene that produces a white belt around the animal's body is dominant over its allele for a uniformly colored body.
Another independent gene produces fusion of the two hoofs on each foot (syndactyly); it is dominant over its allele, which produces normal hoofs. Suppose a uniformly colored hog homozygous for syndactyly is mated with a normal-footed hog homozygous for the belted character. What would be the phenotype of the Fl? If the FI individuals are allowed to breed freely among themselves, what genotypic and phenotypic ratios would you predict for the F2?

10. In watermelons the genes for green color and for short shape are dominant over their alleles for striped color and for long shape. Suppose a plant with long striped fruit is crossed with a plant heterozygous for both these characters. What phenotypes would this cross produce and in what ratios?

1I. In the fruit fly, Drosophila melanogaster, vestigial wings and hairy body are produced by two recessive genes located on  different chromosomes. The normal alleles, long wings and hairless body, are dominant. Suppose a vestigial-winged hairy male  is crossed with a homozygous normal female. What types of progeny would be expected? If the Fl from this cross are permitted to mate randomly with each other, what progeny would be expected in the F2? Show complete genotypes, phenotypes, and ratios for each generation.

12. A dominant gene, A, causes yellow color in rats. The dominant allele of another independent gene, R, produces black coat color. When the two dominants occur together (A/-RJ-), they interact to produce gray. Rats of the genotype ala rlr are cream colored.
If a gray male and a yellow female, when mated, produce offspring approximately 3/8 of which are yellow, 3/8 gray, 1/8 cream, and 1/8 black, what are the genotypes of the two parents?


13. What are the genotypes of a yellow male rat and a black female that, when mated, produce 46 gray and 53 yellow   offspring?

great Job