Probability Genetics

In a certain breed of dogs, brown fur (B) is a dominant trait over yellow fur (b). Gregory owns a brown female. She produced a litter of offspring that includes two brown and two yellow puppies. The only thing Gregory knows about the male is that he was of the same breed. Which of the following represents the genotype combinations that are possible for Gregory’s dog and the father of this litter of puppies?

• Mother = BB x Father = bb

• Mother = BB x Father = Bb

• Mother = Bb x Father = Bb

• Mother = Bb x Father = bb

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The pedigree shown here presents information about the instances of sickle cell anemia in the Miller family. According to the data in the pedigree, which of Susan Miller’s children are affected with sickle cell anemia?

• One son and one daughter

• Both of her sons

• Both of her daughters

• All of her children

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The Punnett square predicts the ratio of genotypes in the offspring, based on the genotypes of the parents. The Punnett square below examines the chance of offspring having freckles, which is a dominant trait.

Based on the Punnett square, what is the probability that the offspring will have freckles?

• 25%

• 50%

• 75%

• 100%

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NGSS.HS-LS3-1

In pea plants, tallness (T) is dominant to shortness (t). What are the predicted percentages of the genotypes of the offspring if a homozygous short plant is crossed with a heterozygous tall plant?

• 25 percent Tt, 75 percent tt

• 25 percent tall, 75 percent short

• 50 percent Tt, 50 percent tt

• 50 percent tall, 50 percent short

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A dihybrid cross is created from plants that are heterozygous for both round seeds and yellow seed color. What is the ratio of offspring that have round seeds and yellow seed color?

• 1:16

• 3:16

• 9:16

• 16:16

The Punnett square predicts the ratio of genotypes in the offspring, based on the genotypes of the parents. In this cross, tallness (H) is dominant to shortness (h).

Based on the Punnett square, what is the phenotype of the offspring?

• Hh

• HH

• tall

• short

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NGSS.HS-LS3-1

A plant can produce either purple flowers or white flowers. What is the probability of purple-flowered offspring if two plants that are heterozygous for purple flowers are crossed?

• 1:4

• 2:4

• 3:4

• 4:4

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Purple flowers are dominant over white flowers. A heterozygous purple flower is crossed with another heterozygous purple flower. What will the ratio of purple to white be?

• 3:1

• 1:3

• 2:2

• 4:0

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In a certain species of plant, the allele for red flowers (R) is dominant over the allele for white flowers (r). If two heterozygous plants are crossed, what is the probability of obtaining a plant with white flowers?

• A) 1:4

• B) 1:2

• C) 3:4

• D) 4:4

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In a genetic experiment, a homozygous dominant plant is crossed with a homozygous recessive plant. What will be the genotype of the offspring?

• A) Homozygous dominant

• B) Homozygous recessive

• C) Heterozygous

• D) Cannot be determined

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