GENETICS CHAPTER 3 HOMEWORK

In pea plants, plant height is controlled by a single autosomal dominant gene. Tall plants (H) are dominant to short plants (h). In a cross of two tall heterozygous plants, which phenotype ratio is expected from the resulting offspring?

3:1

In humans, oculocutaneous (OCA) albinism is a collection of autosomal recessive disorders characterized by an absence of the pigment melanin in skin, hair, and eyes. That is, normal pigmentation (A) is dominant over albino characteristics (a). For this question, assume it is a single gene with two alleles. If both parents have normal pigmentation, what are all of the possible genotypes that may be observed in their offspring?

AA, Aa, or aa

Of the following ideas postulated by Gregor Mendel, which one requires at least two genes to be demonstrated?

Genes assort independently in humans

In fruit flies, gray bodies (G) are dominant over black bodies (g), and brown pigments (N) are dominant over yellow pigments (n). Each individual possesses two alleles for each trait. If a fly that is homozygous dominant for both traits is crossed with a fly that is homozygous recessive for both traits, what is the predicted genotype of the offspring?

GgNn

In humans, oculocutaneous (OCA) albinism is a collection of autosomal recessive disorders characterized by an absence of the pigment melanin in skin, hair, and eyes. That is, normal pigmentation (A) is dominant over albinism (a). For this question, assume it is a single gene with two alleles. If two people have normal pigmentation, what possible phenotypes may be observed in their offspring?

Normal pigmentation or albinism

In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are dominant over no spots (s). The genes for these two characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. The F1 are intercrossed to produce the F2. a. What are the phenotypic ratios in the F2? b. If an F1 plant is backcrossed with the bitter, yellow-spotted parent, what phenotypes and proportions are expected in the offspring? c. If an F1 plant is backcrossed with the sweet, nonspotted parent, what phenotypes and proportions are expected in the offspring?

P - BBSS x bbss F1 - BbSs x BbSs a. 9 (bitter w/ spots): 3 (bitter w/ no spots) : 3 (sweet w/ spots) : 1 (sweet w/ no spots) b. 100% bitter with spots . BBSS - 1/4; BbSs - 1/4; BBSs - 1/4; BbSS- 1/4 c. BbSs - Bitter w/ spots - 1/4 ; Bbss - bitter w/ no spots - 1/4 ; bbSs - sweet w/ spots - 1/4 ; bbss - sweet with no spots - 1/4

In cats, curled ears result from an allele, Cu, that is dominant over an allele, cu, for normal ears. Black color results from an independently assorting allele, G, that is dominant over an allele for gray, g. A gray cat homozygous for curled ears is mated with a homozygous black cat with normal ears. All the F1 cats are black and have curled ears. What phenotypes and proportions are expected from the following two crosses?

PHOTOS

The figure below represents a pair of homologous chromosomes. Assign the appropriate term to each component.

PHOTOS