Chapter 9

Question 1

A man with kinky hair has children by a woman with non-kinky hair. They have five children, three of whom have kinky hair. Based on this information alone, what inheritance pattern is seen with the kinky hair trait?

a. pleiotropy
b. multiple allelism
c. linked inheritance
d. incomplete dominance
e. single-gene trait

Answer 1

single-gene trait

Question 2

Which human trait is not considered to be polygenic?

a. blood type
b. hair color
c. behavior
d. eye color
e. height

Answer 2

blood type

Question 3

Which is the best definition for the term “dihybrid”?

a. an individual that has been produced by two generations of controlled breeding
b. an individual with parents that are heterozygous for two traits of interest
c. an individual that contains two different transgenes
d. an individual that is heterozygous for two traits of interest
e. an individual in which recombination has occurred in two places in the genome

Answer 3

an individual that is heterozygous for two traits of interest

Question 4

Little Johnny’s father is incredibly organized, but his mother tends to be messy. When Little Johnny’s aunt notices that all of his binders are labeled and his room is spotless, she claims “you obviously didn’t inherit your mother’s ‘messy’ genes!” What is wrong with this statement?

a. Characteristics, such as organizational skills, are behavioral and environmentally influenced. Therefore, they are not specifically inherited.
b. The organizational-skill gene is Y-linked; therefore, that is why he is organized, like his father.
c. The organizational-skill gene is an X-linked gene; therefore, since Johnny is a boy, he only took after his mother.
d. Nothing is wrong with this statement. Our behaviors, just as much as our physical characteristics, are inherited from our parents.
e. This statement is incorrect because the son may actually have some of his mother’s “messy” genes, too. The gene for organization is recessive.

Answer 4

Characteristics, such as organizational skills, are behavioral and environmentally influenced. Therefore, they are not specifically inherited.

Question 5

Which choice is not an example of pleiotropy?

a. SRY gene: This gene causes fetal gonads to develop as testes shortly after fertilization and is responsible for numerous behavioral characteristics.
b. sickle-cell allele: This allele can disrupt red blood cell oxygen delivery and cause blood cells to be inhospitable to malarial parasites.
c. CFTR gene: A mutation in this gene, which codes for a membrane protein that serves as a channel for chloride ions, leads to the disease cystic fibrosis as well as diabetes and, in males, deterioration of the vas deferens.
d. height: The gene for height can result in various degrees/levels of height, that is, some people are taller than others.
e. PKU disease: A mutation in the gene for a particular enzyme leads to mental retardation and reduced hair and skin pigmentation.

Answer 5

height: The gene for height can result in various degrees/levels of height, that is, some people are taller than others.

Question 6

A student wishes to determine whether the genes that control seed shape (R) and seed color (Y) in pea plants are linked, so they perform a dihybrid cross. What phenotypic ratio would they expect to observe for each trait if these two genes are assorting independently?

a. all tall and all smooth
b. 3:1 for tall and 1:1 for smooth
c. 3:1 for smooth and 1:1 for tall
d. 3:1 for both traits
e. 1:1 for both trait

Answer 6

3:1 for both traits

Question 7

In peas, yellow seeds (Y) are dominant to green seeds (y). A homozygous dominant and a homozygous recessive plant are crossed and have two offspring. These two offspring are then crossed with each other. What are the chances that the second generation of offspring (the offspring of the first offspring) will have yellow seeds?

a. 75%
b. 50%
c. 100%
d. zero
e. 25%

Answer 7

75%

Question 8

Which statement is false?

a. Type AB blood cells produce A and B antigens but neither A nor B antibodies.
b. Type A blood cells produce A antigens and B antibodies.
c. Type B blood cells produce B antigens and A antibodies.
d. Type AB blood cells produce A and B antigens and both A and B antibodies.
e. Type O blood cells produce neither A nor B antigens and produce both A and B antibodies.

Answer 8

Type AB blood cells produce A and B antigens and both A and B antibodies.

Question 9

Suppose you perform a dihybrid cross between two tall pea plants with smooth seeds. If these traits are not linked, what phenotypic ratio would you expect to observe in the offspring for each trait?

a. all tall and all smooth
b. 3:1 for tall and 1:1 for smooth
c. 3:1 for smooth and 1:1 for tall
d. 3:1 for both traits
e. 1:1 for both traits

Answer 9

3:1 for both traits

Question 10

The chance of two separate events occurring together is equal to the product of their separate chances. Two people who are carriers of the recessive Tay-Sachs gene decide to have children. What are the chances this couple will give birth to three children with Tay-Sachs?

a. None. They can’t produce any Tay-Sachs children.
b. 1/64, or 1.56%
c. 1/16, or 12.5%
d. 1/8, or 50%
e. 1/4, or 25

Answer 10

1/64, or 1.56%

Question 11

In snapdragons, flower color is inherited as a trait with incomplete dominance. There is an allele, CW, that produces no pigment, and an allele, CR, that produces red pigment. A plant with the CWCR genotype will produce _____ flowers.

a. petals of alternating color
b. no
c. pink
d. white
e. red

Answer 11

pink

Question 12

Which statement is true regarding a cross between a homozygous albino female giraffe (aa) and a heterozygous pigmented male giraffe (Aa)?

a. There is a 100% chance that the sperm will carry the dominant A allele.
b. Under normal conditions, there is a 99% chance that the mother’s egg will carry the recessive allele.
c. There is a 50% chance that the offspring will be albino.
d. In the event that a homozygous dominant offspring results, it will most likely die due to excessive pigment production.
e. There is a 12.5% chance that the offspring will be an albino female giraffe.

Answer 12

There is a 50% chance that the offspring will be albino.

Question 13

Prior to Mendel:

a. humans observed heredity but could not understand or manipulate it.
b. humans observed, manipulated, and understood heredity and how it worked.
c. humans had no ideas about heredity.
d. humans observed and manipulated heredity but did not understand how it worked.
e. humans knew that heredity was controlled by genes but didn’t know the DNA structure.

Answer 13

humans observed and manipulated heredity but did not understand how it worked.

Question 14

This Punnett square depicts a dihybrid cross between two cats with short, white fur. Use the Punnett square to determine the phenotypic ratio expected from the offspring if both traits are taken into account. IMAGE TO INCLUDE: Figure 9-27, the left half (Punnett square) only.

a. 1 short white: 1 long white: 1 long non-white: 1 short non-white
b. 9 short white: 3 long white: 3 short non-white: 1 long non-white
c. 9 long white: 3 short white: 3 long non-white: 1 short non-white
d. 12 short white: 4 long non-white
e. 10 short white: 1 long white: 1 long non-white: 4 short non-white

Answer 14

9 short white: 3 long white: 3 short non-white: 1 long non-white

Question 15

If two giraffes were crossed, where one is heterozygous for albinism (a) and the other has a homozygous dominant genotype, what would be the expected genotypic and phenotypic ratios?

a. 0 AA: 0 Aa: 1 aa; all albino
b. 2 AA: 0 Aa: 0 aa; all pigmented
c. 2 AA: 2 Aa: 0 aa; all pigmented
d. 1 AA: 2 Aa: 1 aa; 3 pigmented: 2 albino
e. 2 AA: 2 Aa: 0 aa; 4 pigmented: 2 albino

Answer 15

2 AA: 2 Aa: 0 aa; all pigmented

Question 16

In humans, the processing of cholesterol in the bloodstream can be hindered by the mutant allele FH. Few individuals who possess two copies of this allele live past the age of 20, whereas heterozygotes may survive, but with an increased risk of cardiovascular disease compared to individuals who are homozygous wildtype. Which pattern of inheritance explains this phenomenon?

a. recessive
b. carrier
c. incomplete dominance
d. codominance
e. dominance

Answer 16

incomplete dominance

Question 17

In a cross between two tall pea plants with purple flowers, both of which are heterozygotes (TtPp), what phenotypic ratio would you expect to observe for the tall trait?

a. all tall
b. 3 short: 1 tall
c. 3 tall: 1 short
d. all short
e. 1 tall: 1 short

Answer 17

3 tall: 1 short

Question 18

Why do the human traits for red hair and pale skin typically not follow Mendel’s law of independent assortment?

a. The genes for hair color and skin pigmentation are linked.
b. The genes for hair color and skin pigmentation are on separate chromosomes.
c. The law of independent assortment only applies to plants.
d. The genes for hair color and skin pigmentation are recessive traits.
e. The genes for hair color and skin pigmentation follow the law of segregation instead.

Answer 18

The genes for hair color and skin pigmentation are linked

Question 19

Inheriting two copies of a defective gene can cause a person to smell like a rotten fish. Which choice best supports this statement?

a. If a child does not have a parent with fish odor syndrome, then he/she automatically cannot acquire the syndrome.
b. There is no particular gene that can cause a person to smell like a rotten fish; personal hygiene is not inherited.
c. If a person who is a carrier of the fish odor allele has a child with someone who is not a carrier, the child will only smell slightly of rotten fish.
d. A person with fish odor syndrome will always have at least one child with fish odor syndrome.
e. As long as a person has at least one normal version of the FMO3 gene, he/she will not suffer from fish odor syndrome.

Answer 19

As long as a person has at least one normal version of the FMO3 gene, he/she will not suffer from fish odor syndrome.

Question 20

Which pattern of inheritance is observed in the diagram? IMAGE TO INCLUDE: Add CROSS 1 ONLY from figure 9.17 to the question stem.

a. recessive
b. dominance
c. sex-linked
d. incomplete dominance
e. codominance

Answer 20

incomplete dominance

Question 21

According to Mendel’s law of independent assortment:

a. the alleles coding for one trait do not usually influence the inheritance pattern for another trait.
b. skin color and hair texture tend to be inherited together.
c. individuals with cleft chins are likely to have curly hair.
d. individuals with red hair are more likely to have freckles.
e. we can deduce that genes cannot exist as free-floating entities within a cell but must be carried on chromosomes.

Answer 21

the alleles coding for one trait do not usually influence the inheritance pattern for another trait.

Question 22

The AB blood type is an example of which pattern of inheritance?

a. dominant
b. recessive
c. sex-linked
d. codominance
e. incomplete dominance

Answer 22

codominance

Question 23

Which statement about the offspring of a dihybrid cross is true?

a. The genotypic ratios for each trait will be 9:3:3:1.
b. The genotypic ratios for each trait will be 3:1.
c. The genotypic ratios for each trait will be 1:2:1.
d. The phenotypic ratios for each trait will be 1:2:1.
e. The phenotypic ratios for each trait will be 1:1.

Answer 23

The genotypic ratios for each trait will be 1:2:1.

Question 24

A child will definitely develop “fish odor syndrome” if:

a. both parents are carriers of defective FMO3 alleles.
b. the child inherits two copies of the defective FMO3 gene.
c. the mother has fish odor syndrome.
d. at least one parent is a carrier of a defective FMO3 gene.
e. the child inherits one defective version of the FMO3 gene

Answer 24

the child inherits two copies of the defective FMO3 gene.

Question 25

What are the possible genotypes of an individual who has type B blood?

a. IBIB, IB_
b. IBi
c. IBIB
d. IBIB, IBi
e. IBIB, IB IA

Answer 25

IBIB, IBi

Question 26

All of the offspring of a red carnation crossed with a white carnation are pink. The simplest explanation for this pattern of inheritance is:

a. codominance.
b. albinism.
c. sex linkage.
d. incomplete dominance.
e. multiple alleles.

Answer 26

incomplete dominance.

Question 27

If an individual carries only two alleles, is it possible for a single gene to have more than two alleles?

a. Yes, but the alleles that the individual carries then would no longer be inherited as one from the mother and one from the father. The law of segregation does not apply to genes with multiple alleles.
b. Yes, but it results in diseases such as trisomy 21.
c. If a gene had more than two alleles, it would not be dominant or recessive.
d. If a gene had more than two alleles, it would be too variable to be identified as one gene.
e. Yes. More than two possible alleles for a single gene type is called multiple allelism. The alleles for the ABO blood types are an example.

Answer 27

Yes. More than two possible alleles for a single gene type is called multiple allelism. The alleles for the ABO blood types are an example.

Question 28

Even when two genes are located on the same chromosome, they will likely appear to assort independently if they are _____.

a. physically linked
b. close together
c. far from one another
d. genetically linked
e. segregating

Answer 28

far from one another

Question 29

Which statement about a mouse with a heterozygous genotype for albinism (a recessive trait) could be true?

a. Its phenotype will be pigmented with white patches.
b. It will produce all albino phenotypes when crossed with a mate with an albino phenotype.
c. It will have an albino phenotype.
d. It will have a pigmented phenotype.
e. It will produce all pigmented offspring when crossed with a mate with a pigmented phenotype.

Answer 29

It will have a pigmented phenotype.

Question 30

Two genes located close together on the same chromosome may be considered linked while two genes farther apart on the same chromosome may not be considered linked. Which biological process is required for this phenomenon?

a. meiosis
b. dihybridism
c. crossing over
d. mitosis
e. nondisjunction

Answer 30

crossing over

Question 31

Which result of a test-cross between a pigmented alligator (M_) and an albino alligator (mm) would indicate that the pigmented parent is heterozygous?

a. getting even a single albino offspring
b. getting six offspring that are pigmented
c. getting three offspring that are pigmented
d. There is no way to determine the pigmented parental genotype from the proposed cross.
e. Both choices A and B are true.

Answer 31

getting even a single albino offspring

Question 32

What would Gregor Mendel most likely have observed if the genes for pea color and pea shape had been linked?

a. He would have observed more recessive trait plants than in his actual experiment.
b. He would have observed more dominant trait plants than in his actual experiment.
c. He would have observed fewer offspring with traits matching the parent plants than in his actual experiment.
d. He would have observed the same results as in his actual experiment.
e. He would have observed more offspring with traits matching the parent plants than in his actual experiment.

Answer 32

He would have observed more offspring with traits matching the parent plants than in his actual experiment.

Question 33

The distinctive fur color of a Siamese cat is an example of:

a. pleiotropy.
b. albinism.
c. codominance.
d. sex-linkage.
e. environmental effects.

Answer 33

environmental effects.

Question 34

Which statement about Mendel’s law of independent assortment is false?

a. Genes are distributed into gametes individually from each other.
b. True-breeding populations will always pass on their alleles in a linked manner.
c. The chromosomes resulting from meiosis are randomly assorted from all possible combinations of parental chromosomes.
d. Each locus involved in a dihybrid cross is not influenced by the other loci.
e. Each trait is inherited separately from other traits.

Answer 34

True-breeding populations will always pass on their alleles in a linked manner.

Question 35

35. An individual with the genotype HbSHbA will have both normal and sickle-shaped red blood cells. This is an example of:

a. incomplete dominance.
b. dominance.
c. recessivity.
d. codominance.
e. multiple allelism

Answer 35

codominance.

Question 36

If a male with color-blindness (sex-related variety) and a female with normal vision have a color-blind son, what can you infer about the parents?

a. The son inherited a gene for color-blindness from his mother and one from his father.
b. The mother’s father was color-blind.
c. The mother was homozygous for color-blindness.
d. The mother was a carrier for color-blindness.
e. The son inherited the gene for color-blindness from his father.

Answer 36

The mother was a carrier for color-blindness.

Question 37

If a white cat with short fur, who is homozygous dominant for both traits, is crossed with a yellow cat with long fur, who is homozygous recessive for both traits, their offspring will be:

a. dihybrid.
b. polygenic.
c. codominant.
d. pleiotropic.
e. carriers.

Answer 37

dihybrid.

Question 38

Albinism (lack of skin and hair pigmentation) is caused by a recessive autosomal allele. A woman and man, both normally pigmented, have an albino child together. For this trait, what is the genotype of the albino child?

a. heterozygous
b. homozygous recessive
c. homozygous dominant
d. It depends on the environment that the child lives in.
e. It is unknown, because not enough information is provided.

Answer 38

homozygous recessive

Question 39

Which statement about the Rh marker allele is false?

a. The Rh marker results from a single gene with two alleles.
b. An individual’s red blood cells carry the Rh cell surface marker if they have one or two copies of the dominant Rh marker allele.
c. The Rh marker is responsible for the ABO blood types.
d. If an individual has two copies of the recessive allele for the gene, they do not have any Rh markers, and are therefore are described as “negative,” for example, B– or B negative.
e. If a person has one or two copies of the dominant Rh marker allele then their blood type is noted as “positive,” for example , B+ or B positive.

Answer 39

The Rh marker is responsible for the ABO blood types.

Question 40

Which choice best explains the mechanism by which a pair of linked alleles could become separated?

a. independent assortment
b. spindle fibers
c. segregation
d. meiosis
e. recombination

Answer 40

recombination

Question 41

Which statement about Mendel’s genetics experiments is false?

a. Mendel controlled which plant was “crossed” with another by using “pollen dusting.”
b. True-breeding, to Mendel, meant that certain plants always produced the same version of traits as their parents.
c. Mendel studied only seven traits found in pea plants.
d. Mendel believed that a tiny, pre-formed pea plant was passed via pollen to a pea plant egg.
e. Mendel used relatively unsophisticated methods and good experimental design to learn about inheritance.

Answer 41

Mendel believed that a tiny, pre-formed pea plant was passed via pollen to a pea plant egg.

Question 42

Which blood type is incorrectly matched with its potential recipient?

a. Type AB can only receive from type A, B, or AB.
b. Type A can only receive from type A or type O.
c. Type O can only receive from type O.
d. Type B can only receive from type B or type O.
e. Negative blood types can only receive negative blood.

Answer 42

Type AB can only receive from type A, B, or AB.

Question 42

Why was it a stroke of luck that Gregor Mendel chose pea plants for his studies (in terms of being able to observe the effects of one of the laws of genetics)?

a. The traits he studied were controlled by genes closely linked together in the pea genome.
b. The traits he studied were sex-linked.
c. The traits he studied were controlled by genes not closely linked together in the pea genome.
d. Recombination does not occur in pea chromosomes.
e. Pea plants have very few genes.

Answer 42

The traits he studied were controlled by genes not closely linked together in the pea genome.

Question 43

An allele is dominant when it:

a. is more advantageous than other alleles.
b. is more common than other alleles.
c. increases the reproductive fitness of the organism that inherits it.
d. is homozygous.
e. masks the effects of another allele.

Answer 43

masks the effects of another allele.

Question 44

Which description of an allele is false?

a. An allele can be one of several alternative forms of a gene.
b. Each allele will assort independently from alleles on other chromosomes.
c. An allele can be identical to or different from its sister allele for any gene in a somatic cell.
d. Each allele is located at a unique locus on the chromosome.
e. Each allele can be dominant or recessive.

Answer 44

Each allele is located at a unique locus on the chromosome.

Question 45

What is the probability that an individual who is heterozygous for a given allele will pass that allele to her/his gametes?

a. 50%
b. 25%
c. 0%
d. 75%
e. 100%

Answer 45

50%

Question 46

If, when in a heterozygous state, one allele masks the effect of the other allele, the masked allele is referred to as:

a. segregated.
b. inherited.
c. codominant.
d. dominant.
e. recessive.

Answer 46

recessive.

Question 47

A diploid individual with two identical alleles for a particular gene is said to be:

a. homozygous for that gene.
b. codominant for that gene.
c. pleiotropic for that gene.
d. heterozygous for that gene.
e. autosomal for that gene.

Answer 47

homozygous for that gene.

Question 48

A type of family tree that is used to document the inheritance of traits over many generations is known as:

a. a phenotype.
b. a pedigree.
c. a Punnett square.
d. a test-cross.
e. a DNA fingerprint.

Answer 48

a pedigree.

Question 49

Which statement best explains Mendel’s law of segregation?

a. Both alleles are put into a gamete, and during development, the two gametes segregate by chance.
b. If someone is heterozygous, they exemplify Mendel’s law of segregation.
c. Both gametes and fertilized eggs have two copies of each gene.
d. Organisms have one copy of a gene, and they place that copy into each gamete during the process of meiosis.
e. Of the two copies of each gene everyone carries, only one of the two alleles gets put into each gamete.

Answer 49

Of the two copies of each gene everyone carries, only one of the two alleles gets put into each gamete.

Question 50

What is the purpose of a test-cross?

a. A test-cross allows a breeder to see how quickly it takes to go from generation to generation for a particular organism.
b. A test-cross can reveal an unknown genotype.
c. A test-cross is just another term for an experimental cross between two unknown organisms.
d. A test-cross can demonstrate the efficiency of breeding.
e. A test-cross can reveal an unknown internal phenotype.

Answer 50

A test-cross can reveal an unknown genotype.

Question 51

Which description is not included in the definition of a phenotype?

a. chemicals an individual produces, such as in digesting lactose
b. features visible to the naked eye, such as height
c. all the genes an individual carries
d. certain behaviors an individual exhibits
e. outward appearance

Answer 51

all the genes an individual carries

Question 52

The impact of a single gene on more than one characteristic is called:

a. codominance.
b. polygenic inheritance.
c. homozygosity.
d. pleiotropy.
e. additive effects.

Answer 52

pleiotropy.

Question 53

Which factor did NOT contribute to the success of Mendel’s research?

a. He chose an organism that easily produced large numbers of offspring
b. He chose a good organism to study, that is, pea plants, which had clear-cut phenotypes.
c. He chose to focus on easily categorized traits, such as round or wrinkled.
d. He began his studies by first repeatedly breeding together similar plants until he had many distinct populations, each of which was unvarying for a certain trait.
e. He did not utilize any true-breeding organisms in order to study various types of traits.

Answer 53

He did not utilize any true-breeding organisms in order to study various types of traits.

Question 54

What is a linked gene?

a. a gene that causes mutations, such as trisomy 21
b. two different genes are found on the same chromosome
c. a gene that suppresses the effects of another gene
d. an abnormality where two chromosomes are connected due to some sort of mutation
e. any gene that exhibits an outward effect; in fact, all genes are linked

Answer 54

two different genes are found on the same chromosome

Question 55

Which option best describes a sex-linked trait?

a. only inherited by females
b. a trait that is controlled by a gene on a sex chromosome
c. a trait that involves the reproductive system
d. always heterozygous
e. only inherited by males

Answer 55

a trait that is controlled by a gene on a sex chromosome

Question 56

Sex-linked traits:

a. are controlled by genes on the X and Y chromosomes.
b. are only controlled by genes on the Y chromosome.
c. appear more frequently in females if they are recessive.
d. cannot be visualized using a pedigree.
e. are only inherited from the father.

Answer 56

are controlled by genes on the X and Y chromosomes.