Genetics Questions

1. Alternate forms of a gene that govern the expression of the same trait and that occur at the same positions on homologous chromosomes are called:
a. Chromatids.
b. mRNA.
c. Gametes.
d. Alleles.
e. Autosomes.

2. In Mendel's garden peas, the yellow color is dominant to the green. Additionally, smooth seeds are dominant to wrinkled seeds. In a dihybrid cross, a plant has a P generation consisting of smooth yellow and wrinkled green. The F1 generation consists of 100% smooth yellow. These plants are now self-fertilized and the F2 generation would show a phenotype ratio of:

a. 9:3:3:1
b. 3:1:1:3
c. 2:1:1:0
d. 2:1:1:2

3. For codominant genes, the standard procedure of using capital and lowercase letters for the different alleles is inadequate. For codominant genes, a superscript is used. For example, the human blood type A allele is indicated as "IA" and the Type B allele is indicated as "IB." The recessive allele that is responsible for Type O blood is still given the lowercase letter "i." In a family of six children, two are blood Type O, two are blood Type AB, one is blood Type B, and another Type A. What are the possible genotypes of the parents?
a. IAi x IAIB.
b. IBi x IAIB.
c. IAi x IBi.
d. IAIB x ii.

4. The fact that all seven of the garden pea traits studied by Mendel obeyed the principle of independent assortment means that:

a. Seven pairs of alleles determining these traits behave as if each is on separate chromosome pairs.
b. Garden pea plants produce gametes with seven chromosomes.
c. Garden pea plants have seven pairs of chromosomes.
d. Seven pairs of alleles determining these traits are on the same pair of homologous chromosomes.

5. A cross between two homozygous individuals (RR)(rr) at two incompletely dominant genes will produce an expected phenotypic ratio in the F2 generation of:
a. 15:1.
b. 1:2:1.
c. 9:3:3:1.
d. 1:2:2:4:1:2:1:2:1.

6. Duchenne muscular dystrophy is caused by a sex-linked allele. Its victims are almost always boys who die before the age of 20. Why is this disorder almost never seen in girls?
a. Sex-linked traits are never seen in girls.
b. Males carrying the allele don't usually live long enough to reproduce.
c. The allele is carried on the Y chromosome.
d. Girls must receive the allele from both their mother and their father.

7. Hemophilia is a sex-linked disorder. Which is the best prediction of the offspring if the mother is a carrier and the father has hemophilia?
a. All sons and daughters will have hemophilia.
b. All sons will have hemophilia and all daughters will be normal.
c. 50% of the sons will have hemophilia and 50% of the daughters will have hemophilia.
d. 25% of the daughters will have hemophilia and all of the sons will have hemophilia.

8. When can a trait be expressed when only one allele for that trait is present?
a. When the allele is recessive.
b. When the allele is on the X chromosome in a female.
c. When the allele is on the X chromosome in the male.
d. When the allele is on the Y chromosome in the female.

9. A female is born with color blindness. What must have happened?
a. Her father is colorblind and her mother is not.
b. Her mother is colorblind and her father is not.
c. Her father is colorblind and her mother is a carrier of the trait.
d. Her mother is colorblind and her father is a carrier of the trait.

10. If a disease is caused by a dominant allele, it means that a person with the disease:
a. Will always pass it on to their children.
b. Only needs to have one copy of the allele that causes the disease in order to have symptoms of the disease.
c. Will only pass it on to children if their mate also has the disease.
d. Is more likely to be male.