GENETICS EXAM 1: CH 3

What term describes an individual possessing two of the same alleles at a gene locus?

homozygous

Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU. What is the probability that a sperm from the father will contain the PKU allele?

1/2

Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU. What is the probability that an egg from the mother will contain the PKU allele?

1/2

If an Aa individual is crossed to an aa individual, what will be the phenotypic ratio in the offspring?

1:1

What will be the genotypic ratio in the offspring of two Aa parents that are crossed with each other?

1:2:1

The principle of independent assortment involves at least how many different gene pairs?

2

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 pea plants, the allele for red flower color, F, is completely dominant to the allele for white flower color, f. Complete the Punnett square showing the genotypes possible among the offspring when two heterozygous individuals are crossed. Use the information from the Punnett square to answer the second question. In this cross between two heterozygous pea plants, what are the chances that an offspring with red flowers will be produced?

75%

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. What will be the phenotypic ratio in the F2?

9/16 bitter fruit, yellow spots; 3/16 bitter fruit, no spots; 3/16 sweet fruit, yellow spots; and 1/16 sweet fruit, no spots

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)(A) is dominant over albino characteristics (𝑎)(a) . For this question, assume the phenotype is determined by 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

A cross between an AABB individual and an aabb individual will produce what type of offspring?

All will be AaBb

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

Genes assort independently in diploids.

In fruit flies, gray bodies (G) are dominant over black bodies (g), and red eyes (R) are dominant over orange eyes (r). 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?

GgRr

Which organism did Gregor Mendel use to discover the basic principles of genetics?

Pisum sativum (pea plant)

When Mendel crossed a plant homozygous for round seeds to another plant homozygous for wrinkled seeds, he found that all the progeny had round seeds. How is this explained?

The allele for round seeds is dominant to the allele for wrinkled seeds.

Which of the statements can be concluded from Gregor Mendel's experiments with pea plants?

The inheritance of alleles of one gene does not affect the inheritance of alleles of another gene. Two recessive alleles are necessary for a recessive phenotype.

How is a true breeding round‑seeded pea plant different from a hybrid round‑seeded pea plant?

They have the same phenotype but different genotypes.

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)(A) is dominant over albino characteristics (𝑎)(a) . For this question, assume the phenotype is determined by a single gene with two alleles. If both parents display the albino phenotype, what are all of the possible genotypes that may be observed in their offspring?

aa only

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 both parents display the albino phenotype, what possible phenotypes may be observed in their offspring?

albinism only

What is a cross that occurs between two individuals that differ in two characteristics?

dihybrid cross

Mendel's principle of segregation can be explained by what process?

meiosis

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)(A) is dominant over albinism (𝑎)(a) . For this question, assume the phenotype is determined by 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

What is the physical appearance or manifestation of a characteristic called in genetics?

phenotype

An individual possesses two alleles at a locus and these two alleles separate when gametes are formed, one allele going into each gamete. This genetic concept is known as the

principle of segregation.