Unit Test Answers

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A scientist is studying fruit fly wings. Straight wings are dominant, and curly wings are recessive. Which statement correctly describes the F1 generation if a straight-winged parent is crossed with a curly-winged parent and if both parents are true breeding?

The offspring will have two genes for straight wings.

The offspring will produce only gametes that have genes for curly wings.

The offspring will have one allele for straight wings and one allele for curly wings.

The offspring will have only one kind of allele for the gene that determines wing type.

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Which allele combination represents a male who has an X-linked recessive disorder?

XrY

XRY

XrXr

XRXr

Which type of scientific statement is defined as a hypothesis or group of hypotheses that can be accepted as true based on repeated experimentation with similar results?

hypothesis

theory

law

probability

The results of Thomas Hunt Morgan’s last cross are shown in the Punnett square below. Which of Thomas Hunt Morgan's hypotheses was valid based on these results?

White eyes are lethal in female Drosophila.

White eyes are lethal in male Drosophila.

Female Drosophila with white eyes are homozygous recessive.

White eyes are the dominant trait in female Drosophila.

In peas, yellow seed color (Y) is dominant to green seed color (y). Which describes an organism that has nonidentical alleles for seed color?

yy and has green seeds

Yy and has yellow seeds

YY and has yellow seeds

Yy and has green seeds

Which Punnett square represents a cross between two parents that are heterozygous for purple flowers?

A Punnett square is shown. The columns are labeled Upper F and f. The rows are labeled Upper F and f. Clockwise from upper left the boxes contain: Upper F Upper F, Upper F f, Upper F f, f f.

A Punnett square is shown. The columns are labeled f and f. The rows are labeled f and f. Clockwise from upper left the boxes contain: f f, f f, f f, f f.

A Punnett square is shown. The columns are labeled Upper F and Upper F. The rows are labeled Upper F and Upper F. Clockwise from upper left the boxes contain: Upper F Upper F, Upper F Upper F, Upper F Upper F, Upper F Upper F.

A Punnett square is shown. The columns are labeled Upper F and Upper F. The rows are labeled Upper F and f. Clockwise from upper left the boxes contain: Upper F Upper F, Upper F Upper F, Upper F f, Upper F f.

A pea plant exhibits a recessive trait. Which statement is most likely true about the plant?

The plant is identical to its parent plant.

The plant has different alleles for the gene that codes for the trait.

The plant has two identical alleles for the gene that codes for the trait.

The plant does not have the same genes for the trait as its parent plant.

In peas, yellow seed color (Y) is dominant to green seed color (y). A homozygous green seed pea plant is crossed with a heterozygous yellow seed pea plant. What is the predicted phenotypic ratio of the offspring based on seed color?

50 percent yellow, 50 percent green

50 percent YY, 50 percent yy

100 percent yellow, 0 percent green

100 percent Yy, 0 percent yy

Glaucoma is a leading cause of blindness. Studies have linked a common form of glaucoma to three genes and more than 20 genetic loci. Which best describes glaucoma?

a recessive trait that requires multiple recessive alleles to be expressed

a polygenic trait that is influenced by the alleles of several genes

a codominant trait that is expressed more often when more dominant alleles are present

a dominant trait that depends on the presence of only one of many dominant alleles

Mary has type A blood. Her son Bill has type AB blood. Which blood type does Bill's dad have if he is homogenous for blood type?

In the F2 generation of Mendel’s crosses,

all plants had the dominant trait.

half of the plants had the dominant allele.

all plants had both the dominant and recessive alleles.

one in four plants had two alleles for the recessive trait.

In a dihybrid cross for round and yellow seeds (RrYy x RrYy), what is the probability of having green and wrinkled seeds?Key: R = round r = wrinkled Y = yellow y = green

1:16

3:16

8:16

9:16

Which was most likely an effect on society that resulted from improvements in blood handling during World War I and World War II?

More soldiers died as a result of incorrect blood typing.

More soldiers who had lost a limb returned home.

More donations were needed as a result of poor storage techniques.

More organizations spoke out against the war.

Gregor Mendel used pea plants that were heterozygous for each of two traits—seed color and seed shape—to generate a dihybrid cross. The phenotypic ratio of the resulting offspring was nine with round and yellow seeds, three with round and green seeds, three with wrinkled and yellow seeds, and one with wrinkled and green seeds. From these results, what could Mendel conclude?

Traits are inherited as pairs, sets, or groups.

Traits that are dominant mask traits that are recessive.

Gametes carry one allele for each trait.

Traits are passed independently of one another.

If a person has type B blood, which statement describes the antibodies present in his or her blood?

Only anti-A antibodies are present.

Only anti-B antibodies are present.

Both anti-A and anti-B antibodies are present.

Neither anti-A nor anti-B antibodies are present.

Round seeds and yellow seed color are dominant to wrinkled seeds and green seed color. What is the probability of having offspring that have wrinkled seeds and yellow seed color for the cross RRYY ´ RrYy?

0 percent

25 percent

50 percent

100 percent

A purebred plant that has yellow flowers is crossed with a purebred plant that has white flowers. All the offspring have yellow flowers. Which conclusion about yellow flowers is supported by these results?

Yellow flower color is a dominant trait.

Yellow flower color is a recessive trait.

Yellow flower color is a heterozygous trait.

Yellow flower color is a monohybrid trait.

Pedigrees are used to help geneticists understand how traits are inherited between generations. The Romanovs, a Russian royal family, had a history of hemophilia, a sex-linked disorder that is determined by a recessive allele on the X chromosome.What is the best evidence to prove that Irene was heterozygous for hemophilia?

Elizabeth is not a carrier for the trait.

Tatiana carried the recessive allele.

Her brother has hemophilia and her sister is a carrier.

Two of her sons have hemophilia and one does not.

Hemophilia is an X-linked recessive disorder that is passed through generations and can be traced by using a pedigree. In the pedigree that is shown, which represents Irene's allele combination?

XhXh

XHXh

XHXH

XhY

Which of Mendel’s generations was allowed to self-pollinate?

F1 generation

P generation

F1 generation and F2 generation

P generation and F2 generation

The table below summarizes Mendel’s results for the F2 generation.Mendel’s ResultsPlant height787 tall277 shortFlower color705 purple224 whitePod color428 green152 yellowPod shape882 inflated299 constrictedSeed color6,022 yellowx greenSeed shape5,474 smooth1,850 wrinkledWhat number should replace the letter x in the “Seed color” row?

18,066

3,011

207

2,001

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

Which inheritance pattern results when parents with pure traits are crossed and the resulting offspring have traits that appear to be a blend of the parents' traits?

incomplete dominance

codominance

Mendelian inheritance

polygenic inheritance

Which symbol is used to label a male that expresses a sex-linked disorder on a pedigree?

An empty circle.