Question

1. If two strains of true-breeding plants that have different alleles for a certain character are crossed, their progeny are called

a. the P generation.

b. the F₁generation.

c. the F₂generation.

d. F₁crosses.

e. F₂progeny.

2. Mendel’s crossing of spherical-seeded pea plants with wrinkled-seeded pea plants resulted in progeny that all had spherical seeds. This indicates that the wrinkled-seed trait is

a. codominant.

b. dominant.

c. recessive.

d. Both a and b

e. Both a and c

3. Segregation of alleles occurs

a. during gamete formation.

b. at fertilization.

c. during mitosis.

d. during the random combination of gametes to produce the F₂generation.

e. only in monohybrid crosses.

4. A particular genetic cross in which the individual in question is crossed with an individual known to be homozygous for a recessive trait is referred to as a

a. parental cross.

b. dihybrid cross.

c. filial generation mating.

d. reciprocal cross.

e. test cross.

5. A dihybrid cross

a. results in a genotypic ratio of 2:1.

b. involves genes located on the sex chromosomes.

c. results in offspring of lower quality than that of the parents.

d. results in two different phenotypes in the F₂generation.

e. is a cross between identical double heterozygotes.

6. In Mendel’s experiments, if the allele for tall (T) plants were incompletely dominant over the allele for short (t) plants, what offspring would have resulted from crossing two Ttplants?

a. 1⁄4 tall; 1⁄2 intermediate height; 1⁄4 short

b. 1⁄2 tall; 1⁄4 intermediate height; 1⁄4 short

c. 1⁄4 tall; 1⁄4 intermediate height; 1⁄2 short

d. All tall offspring

e. All intermediate height offspring

7. It has been found that at a certain locus of the human genome, 200 different alleles exist in the population. Each person has at most _______ alleles.

a. 1

b. 2

c. 100

d. 200

e. 400

8. Despite the law of independent assortment, when two loci are on the same chromosome, the phenotypes of the progeny sometimes do not fit the predicted phenotypes due to

a. translocation.

b. inversions.

c. chromatid affinities.

d. linkage.

e. reciprocal chromosomal exchanges.

9. A human male carrying an allele for a trait on the X chromosome is

a. heterozygous.

b. homozygous.

c. hemizygous.

d. monozygous.

e. holozygous.

10. Y-linked genes include a gene that produces hairy pinnae (the external ear). A male with hairy pinnae will pass this trait

a. usually to his sons, but occasionally also to a daughter.

b. only to his sons.

c. only to his daughters.

d. only to his grandsons.

e. to all of his children if the mother is a carrier.

Answer 1

1) Option 'b' is the correct answer.

The first filial generation of two true-breeding parents for a certain trait is termed as F1 generation. The parental generation is referred to as P generation, while the second generation resulting from the selfing of F1 generation is known as F2 generation.

2) Option 'c' is the correct answer.

A dominant trait is always expressed in the phenotype of heterozygote obtained in the F1 generation resulting from the cross between two pure breeding parents for a trait. In the above example, the F1 generation have all spherical seeds, while the wrinkled seeds are not present. This means that the allele for wrinkled gene is recessive and it's expression is halted because of the presence of the dominant allele.

3) Option 'a' is the correct answer.

Segregation of gametes occurs via meiosis during gamete formation when reductional division happens so that the gametes only have one of the two alleles for a trait.

4) Option 'e' is the correct answer.

Test cross is defined as the cross unknown individual and the individual known to be homozygous recessive for the trait. This cross can be used to determine if the unknown individual is homozygous or heterozygous for the trait.