Genetics Test Review The allele for brown eye

Genetics Test Review

• The allele for brown eye color is dominant over blue. A brown-eyed woman (whose father had blue eyes) married a man with blue eyes (whose mother was brown-eyed). What genotypic and phenotypic ratios would you expect in their children?

• Nystagmus is a condition in humans in which those affected have eyeballs that roll involuntarily. The genes for this trait are incompletely dominant. A normal man marries a woman who is slightly nystagmus. What is the chance that their children will be affected?

• A woman with blood type B marries a man. They have 3 kids. One is type B, the other 2 are type O. What are the genotypes of everyone in the family?

• A dominant gene is responsible for the gray body color of fruit flies: its recessive allele produces black body color. A cross of a gray female with a black male produces 52 black and 58 gray flies. What are the genotypes of the parents?

• In humans the size of mouth is codominant. There are 3 sizes, small, medium and large. Assign the symbols for the alleles and do the following crosses and tell the expected phenotypes. • small x medium • medium x large • What would the genotypes of the parents have to be so that the parents could have 3 children with different phenotypes?

• In pea, plants tall is dominant over short. A tall plant is crossed with a short one producing offspring of which about ½ are tall and ½ are short. What are the genotypes of the parents?

• Some miscellaneous, but related questions: – How many chromosomes do you have per trait – What is a gene? – How many chromosomes do you have in each cell?