Genetics question on genotypes.?

Question

1. Brown eyes are dominant over blue eyes. The expected F1 generation from a cross between a homozygous brown-eyed woman and a blue-eyed man would be:

2. In guinea pigs black is dominant over brown. If two heterozygous black guinea pigs are bred, _____ out of 4 offspring should be black.

3. Assume that long ears (L) are dominant over short ears (l) in rabbits. A long-eared female mates with a short-eared male and produces 4 long-eared bunnies and 1 short -eared bunny. The genotypes of the 2 parents are:


4. Blue flowers are produced by a dominant gene. The recessive allele produces white flowers. In a test cross, a plant with blue flowers of undetermined genotype is crossed with a:

5. Which of the following is (are) the correct gamete(s) for an individual with the genotype RRYy?
A. R, R, Y, Y.
B. RRYy.
C. RR, Yy.
D. RY, Ry.

Answer 1

1. Female is BB, male is bb, so all offspring would be Bb--All brown-eyed

2. Bb X Bb will give 3/4 B_ (black) and 1/4 bb (brown)

3. Female is L_, male is ll. Since some offspring are ll (short-eared), then female MUST be Ll.

4. A test cross is always between an individual with the dominant phenotype with a homozygous recessive. So, in this case, you are crossing a blue-flower with a white flower.

5. Since individual has genotype RRYy, you are dealing with two different genes. Each gamete will have one allele of each of the two genes, so the gametes will be RY and Ry.

Answer 2

1. genotype Bb, phenotype 100% brown

2. 3 out of 4; 1 BB, 2 Bb, and the last one bb (brown)

3. Long-eared female has genotype Ll, or there wouldn't be ANY short-eared bunnies; short-eared male has genotype ll

4. In a testcross, the plant with the dominant phenotype and undetermine enotype is crossed with a plant that is homozygous recessive for the same trait.

5. D--the individual will have one copy of each allele per gamete. The only choice for RR is R, so each gamete will have a R; the choices for Yy are Y and y, so a gamete could be either RY or Ry.

Answer 3

Father - Heterozygous Father's Father - Homozygous dominant or Heterozygous Father's mom - Homozygous recessive mom - Homozygous recessive mom's Father - Heterozygous mom's mom - Heterozygous Son - Homozygous recessive