2 Factor Crosses
Show all work on a separate sheet of paper. Be neat!
1. In a certain type of hamster, tan color (T) is completely dominate over brown and a curly coat (C) is
completely dominant over a smooth coat.
A. Identify the 2 traits and their corresponding alleles on your paper (include letters for each allele).
B. Write down the P cross and the F1 genotypes & phenotypes if a homozygous tan, smooth hamster
is bred to a brown homozygous curly hamster.
2. In tomatoes yellow fruit color (r) and dwarf vine size (t) are recessive to red fruits and tall vines. A
homozygous red, homozygous tall plant is crossed with a yellow, dwarf plant.
A. Write down the 2 traits and their corresponding alleles.
B. Write down the P1 cross.
C. Write the genotypes & phenotype of the F1 generation.
D. Write down the genotype & phenotypes for the F2 generation.
3. In Drosophila (fruit fly), vestigial or small wings (w) and ebony body color (c) are due to separate
recessive genes. The dominant alleles are normal wings and gray body color. Complete the following if a
vestigial, ebony female is crossed with a completely homozygous long winged, gray male.
A. Write down the P1 cross
B. Genotypes & phenotypes of F1 generation?
C. What genotypes & phenotypes would you expect for theF2 generation?
4. Some dogs bark when trailing, others are silent. The barking trait is believed to be due to a dominant gene
(B), silence to the recessive gene. Erect ears (E) are dominant over drooping ears. What kind of pups
would be expected from a heterozygous erect-eared, heterozygous barker mated to a droop-eared, silent
trailer?
A. Write the P1 cross using the correct letters.
B. Genotypes & phenotypes of F1 generation?
5. In Drosophila the red-eye color is dominant over the white-eye color (r) and normal length wings (N) is
dominant over vestigial, short, wings. A heterozygous red-eyed fly with vestigial wings is mated to a
white-eyes fly with homozygous normal wing.
A. Write the P1 cross.
B. What percentage of flies are alike in the F1 generation?
C. Write the F1 cross if 2 different flies are mated.
D. Genotypes & phenotypes of F2 generation?
6. A homozygous green (G) frog with spotted coat (S) mates with a female that is a green hybrid carrying
the recessive gene for cream color (g) and has a plain coat (no spots).
A. Write the different gametes produced by the male & female frog.
B. Write the P1 cross.
C. Give the genotypes and phenotypes for the F1 generation.