GENETIC TEST REVIEW SHEET…

  • Be able to use basic genetic terms (differentiate between genotype and phenotype, know the difference between homozygous and heterozygous)
  • Work out monohybrid & dihybrid crosses forward & backwards, determining phenotype and genotypes.
  • Determine gender (XX and XY)
  • Distinguish between sex-determined links and autosomnal traits.
  • What is meiosis, where does it occur and what is the end result?
  • Know other patterns of inheritance: Incomplete inheritance, codominance, multiple alleles, polygenetic traits, environmental influences, F1, F2 and basic meiosis

Sample problems:

1.A plant that is homozygous for red fruit is crossed with a plant homozygous for yellow fruit. All red fruits are produced. If these red fruit offspring are crossed with each other, what is the probability of offspring producing red fruit?

2. In a plant species, the trait for bright yellow flower color is dominant over the trait for white flower color. Two plants with bright yellow flowers are crossed, and some offspring have white flowers. Two of those white offspring are then crossed. What color would you expect to see in the offspring of this second cross?

3. In Drosophila (fruit flies) the sex-linked trait of red eye color (XR) is dominant over white (Xr). Which is the correct genotype for a red-eyed female fruit fly?

4. In cocker spaniels the allele for a black coat color (B) is dominant over the allele for a brown coat color (b). If a brown cocker spaniel is crossed with a heterozygous black cocker spaniel, which genotype ratio can be expected?

5. Brown eyes are dominant over blue eyes for a particular litter of puppies. What could account for a litter of puppies that had more blue eyes than brown eyes?

6. In cattle, the allele for short horns (S) is dominant over the allele for long horns (s). Two heterozygous short-horn cattle are bred and produced four offspring. What percentage would you expect to have long horns?

7. Two traits were observed for hamsters: color and tail length. For color, black (B) is dominant over tan (b). For tail length, short tails (S) are dominant over long tails (s). What is the genotype for a heterozygous black short-tailed hamster?

8. In guinea pigs, the allele for rough coat (R) is dominant over the allele for smooth coat (r). A homozygous dominant guinea pig and a homozygous recessive guinea pig are mated. Show the possible genotypes of their offspring?

9. In humans, the sex-linked trait of normal blood clotting is dominant to hemophilia. Which of the following shows the genotype for someone who is considered to be a carrier for hemophilia?