Genetics

This Punnett square shows flower color inheritance in snapdragons. What is the expected ratio of red flowers to pink flowers to white flowers in the F2 generation?

1 red: 2 pink: 1 white

A farmer mates a rooster that is purebred for black feathers (BB) with a hen that is purebred for white feathers (bb). Which result would show that feather color is inherited in a pattern of codominance in this strain of chickens?

All of the offspring have both black and white feathers.

In one of Mendel's experiments, a cross between two tall plants produced both tall and short offspring in a 3:1 ratio. Which conclusion about the parent plants is supported by Mendel's model?

Both parent plants were heterozygous (Tt) for height.

Would it be possible to obtain a rabbit with Chinchilla coat color if one parent is white and the other parent has a Himalayan coat color?

No, because the parents have no alleles for Chinchilla.

Mendel established several principles of heredity from his experiments and observations. What did he conclude regarding the inheritance of genes from parents?

Offspring inherit two copies of each gene, one from each parent.

A geneticist crossed homozygous, dominant green pod color pea plants (GG) with homozygous recessive yellow pod color pea plants (gg). All the plants in the F1 generation had green pods.

Half of the plants will have a green pod color, and half of the plants will have a yellow pod color.

In pea plants, height is determined by an allele for tallness (T) that is dominant over an allele for shortness (t). What is the probability that a gamete, selected at random, would carry the short allele (t) in a cross of heterozygous tall pea plants?

1/4

In tomatoes, red fruit (R) is dominant over yellow fruit (r). What is the probability that an offspring of plants that are heterozygous (Rr) produce plants with the homozygous recessive (rr) genotype?

1/4

In a cross of purple flowered heterozygous plants (Pp), the letter P represents the allele for purple flowers and the letter p represents the allele for white flowers. What is the probability that an offspring of this cross expresses plants with purple flower phenotypes?

3/4

Punnett squares use mathematical probability to help predict the genotype and phenotype combinations in genetic crosses. Select the steps below that describe how to construct Punnett squares.

All possible combinations of phenotypes are written at both edges of the square.

In guinea pigs, the allele for black fur (B) is dominant over white fur (b). A cross of two black guinea pigs produces three offspring, all of which have black fur. What conclusion can be drawn about the genotypes of the two parent guinea pigs of the cross?

At least one parent was homozygous dominant (BB), but the other parent could be heterozygous (Bb).

Mendel concluded that the genes for pea shape and pea color assort independently of each other. Which experimental finding supports this conclusion?

Each of the 16 outcomes shown in the Punnett square is equally likely, generating a phenotype ratio of 9:3:3:1.

The Punnett square shows the possible allele combinations that result from a two-factor cross between pea plants. Both pea plants are heterozygous for seed shape (round, R, and wrinkled, r) and pod color (green, Y, and yellow, y). Which of the following conclusions can be reached about the offspring of this cross?

For a large number of offspring, there should be a ratio close to 9:3:3:1 of round-seed plants with green pods, wrinkled-seed plants with green pods, round-seed plants with yellow pods, wrinkled-seed plants with yellow pods, because this is the expected ratio with independent assortment of dominant and recessive alleles.

Red blood cells carry antigens on their surfaces coded for by alleles of the gene designated by the letter I. IA is dominant to i and produces antigen A on the surface of red blood cells. The IB allele is also dominant to the i allele and produces antigen B on the surface of red blood cells. The i allele does not produce surface antigens.What types of inheritance are represented by the genetics of human blood types? Select all of the answers that apply.

IA and IB show codominance because both alleles are equally expressed in blood type AB. The human blood type gene is an example of a gene with multiple alleles, IA, IB, i.

A geneticist crossed pure breeding black mice with pure breeding brown mice. All the 992 mice in the F1 generation had black coats. When these mice were crossed, they yielded 961 black coated mice and 317 brown coated mice.

The brown allele is not independent from the black allele and disappears in the F1 generation.

Mendel studied seven traits in pea plants. One of the monohybrid crosses he made was between plants with round seeds and plants with wrinkled seeds. What was a conclusion Mendel drew from the F1 generation of this cross?

The dominant factor, or allele, is for round seeds.

A cross between a plant with red flowers (R = dominant) and a plant with white flowers (r = recessive) yielded 47 plants with red flowers and 51 plants with white flowers. What are the genotypes of the parent plants? Explain.

The results are close to a 1:1 ratio of plants with red flowers to plants with white flowers. Therefore, the genotypes of the parents are Rr and rr.

When the distribution of phenotypes of polygenic traits is graphed, a bell-shaped curve is obtained. Marissa and Gene have phenotypes at the opposite extremes of a polygenic trait. What phenotype will their children most likely have?

They will have the intermediate phenotype for the trait at the middle of the bell curve.

A red-flowered plant is crossed with a white-flowered plant, and the resulting offspring have pink flowers. What is the best explanation for this pattern of inheritance?

This is incomplete dominance, where both alleles are expressed at the same time, giving an intermediate phenotype.