Deck 14: Mendel and the Gene Idea

Question 1

Which of the following about the law of segregation is False?

A)It states that each of two alleles for a given trait segregate into different gametes.
B)It can be explained by the segregation of homologous chromosomes during meiosis.
C)It can account for the 3:1 ratio seen in the F₂ generation of Mendel's crosses.
D)It can be used to predict the likelihood of transmission of certain genetic diseases within families.
E)It is a method that can be used to determine the number of chromosomes in a plant.

Answer 1

E

Question 2

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This suggests

A)that the parents were True-breeding for contrasting traits.
B)incomplete dominance.
C)that a blending of traits has occurred.
D)that the parents were both heterozygous.
E)that each offspring has the same alleles.

Answer 2

D

Question 3

Use Figure 14.1 and the following description to answer the questions below.
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A True-breeding dark-leaved plant is crossed with a light-leaved one, and the F1 offspring is allowed to self-pollinate. The predicted outcome of the F2 is diagrammed in the Punnett square shown in Figure 14.1, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.

Which of the boxes marked 1-4 correspond to plants with dark leaves?

A)1 only
B)1 and 2
C)2 and 3
D)4 only
E)1, 2, and 3

Answer 3

E

Question 4

Use Figure 14.1 and the following description to answer the questions below.
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A True-breeding dark-leaved plant is crossed with a light-leaved one, and the F1 offspring is allowed to self-pollinate. The predicted outcome of the F2 is diagrammed in the Punnett square shown in Figure 14.1, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.

Which of the boxes correspond to plants with a heterozygous genotype?

A)1
B)1 and 2
C)1, 2, and 3
D)2 and 3
E)2, 3, and 4

Question 5

It was important that Mendel examined not just the F₁ generation in his breeding experiments, but the F₂ generation as well, because

A)he obtained very few F₁ progeny, making statistical analysis difficult.
B)parental traits that were not observed in the F₁ reappeared in the F₂.
C)analysis of the F₁ progeny would have allowed him to discover the law of segregation, but not the law of independent assortment.
D)the dominant phenotypes were visible in the F₂ generation, but not in the F₁.
E)many of the F₁ progeny died.

Question 6

What is the difference between a monohybrid cross and a dihybrid cross?

A)A monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents.
B)A monohybrid cross produces a single progeny, whereas a dihybrid cross produces two progeny.
C)A dihybrid cross involves organisms that are heterozygous for two characters and a monohybrid only one.
D)A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations.
E)A monohybrid cross results in a 9:3:3:1 ratio whereas a dihybrid cross gives a 3:1 ratio.

Question 7

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?

A)Prophase I of meiosis
B)Prophase II of meiosis
C)Metaphase I of meiosis
D)Anaphase I of meiosis
E)Anaphase of mitosis

Question 8

The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following?

A)None of the traits obeyed the law of segregation.
B)The diploid number of chromosomes in the pea plants was 7.
C)All of the genes controlling the traits were located on the same chromosome.
D)All of the genes controlling the traits behaved as if they were on different chromosomes.
E)The formation of gametes in plants occurs by mitosis only.

Question 9

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

A)There is considerable genetic variation in garden peas.
B)Traits are inherited in discrete units, and are not the results of "blending."
C)Recessive genes occur more frequently in the F₁ than do dominant ones.
D)Genes are composed of DNA.
E)An organism that is homozygous for many recessive traits is at a disadvantage.

Question 10

Mendel was able to draw his ideas of segregation and independent assortment because of the influence of which of the following?

A)His reading and discussion of Darwin's Origin of Species
B)The understanding of particulate inheritance he learned from renowned scientists of his time
C)His discussions of heredity with his colleagues at major universities
D)His reading of the scientific literature current in the field
E)His experiments with the breeding of plants such as peas

Question 11

Two characters that appear in a 9:3:3:1 ratio in the F₂ generation should have which of the following properties?

A)Each of the traits is controlled by single genes.
B)The genes controlling the characters obey the law of independent assortment.
C)Each of the genes controlling the characters has two alleles.
D)Four genes are involved.
E)Sixteen different phenotypes are possible.

Question 12

Use Figure 14.1 and the following description to answer the questions below.
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A True-breeding dark-leaved plant is crossed with a light-leaved one, and the F1 offspring is allowed to self-pollinate. The predicted outcome of the F2 is diagrammed in the Punnett square shown in Figure 14.1, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.

Which of the plants will be True-breeding?

A)1 and 4
B)2 and 3
C)1-4
D)1 only
E)None

Question 13

Mendel accounted for the observation that traits which had disappeared in the F₁ generation reappeared in the F₂ generation by proposing that

A)new mutations were frequently generated in the F₂ progeny, "reinventing" traits that had been lost in the F₁.
B)the mechanism controlling the appearance of traits was different between the F₁ and the F₂ plants.
C)traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F₁.
D)the traits were lost in the F₁ due to blending of the parental traits.
E)members of the F₁ generation had only one allele for each character, but members of the F₂ had two alleles for each character.

Question 14

A cross between homozygous purple-flowered and homozygous white-flowered pea plants results in offspring with purple flowers. This demonstrates

A)the blending model of genetics.
B)True-breeding.
C)dominance.
D)a dihybrid cross.
E)the mistakes made by Mendel.

Question 15

Pea plants were particularly well suited for use in Mendel's breeding experiments for all of the following reasons except that

A)peas show easily observed variations in a number of characters, such as pea shape and flower color.
B)it is possible to control matings between different pea plants.
C)it is possible to obtain large numbers of progeny from any given cross.
D)peas have an unusually long generation time.
E)many of the observable characters that vary in pea plants are controlled by single genes.

Question 16

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?

A)0%
B)25%
C)50%
D)75%
E)100%

Question 17

A sexually reproducing animal has two unlinked genes, one for head shape (H)and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?

A)HT
B)Hh
C)HhTt
D)T
E)tt

Question 18

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?

A)4
B)8
C)16
D)32
E)64

Question 19

Mendel's second law of independent assortment has its basis in which of the following events of meiosis I?

A)Synapsis of homologous chromosomes
B)Crossing over
C)Alignment of tetrads at the equator
D)Separation of homologs at anaphase
E)Separation of cells at telophase

Question 20

The F1 offspring of Mendel's classic pea cross always looked like one of the two parental varieties because

A)one phenotype was completely dominant over another.
B)each allele affected phenotypic expression.
C)the traits blended together during fertilization.
D)no genes interacted to produce the parental phenotype.
E)different genes interacted to produce the parental phenotype.

Question 21

Use the following information to answer the questions below.
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.
These results indicate which of the following?

A)Brown is dominant to black.
B)Black is dominant to brown and to yellow.
C)Yellow is dominant to black.
D)There is incomplete dominance.
E)Epistasis is involved.

Question 22

Black fur in mice (B)is dominant to brown fur (b). Short tails (T)are dominant to long tails (t). What fraction of the progeny of the cross BbTt × BBtt will have black fur and long tails?

A)1/16
B)3/16
C)3/8
D)1/2
E)9/16

Question 23

A cross between a True-breeding sharp-spined cactus and a spineless cactus would produce

A)all sharp-spined progeny.
B)50% sharp-spined, 50% dull-spined progeny.
C)25% sharp-spined, 50% dull-spined, 25% spineless progeny
D)all spineless progeny.
E)It is impossible to determine the phenotypes of the progeny.

Question 24

The relationship between genes S and N is an example of

A)incomplete dominance.
B)epistasis.
C)complete dominance.
D)pleiotropy.
E)codominance.

Question 25

Use the following information to answer the questions below.
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.
In one type cross of black × black, the results were as follows: 9/16 black
4/16 yellow
3/16 brown
The genotype aabb must result in which of the following?

A)Black
B)Brown
C)Yellow
D)A lethal result

Question 26

Tallness (T)in snapdragons is dominant to dwarfness (t), while red (R)flower color is dominant to white (r). The heterozygous condition results in pink (Rr)flower color. A dwarf, red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F₁ individuals?

A)ttRr-dwarf and pink
B)ttrr-dwarf and white
C)TtRr-tall and red
D)TtRr-tall and pink
E)TTRR-tall and red

Question 27

Skin color in a certain species of fish is inherited via a single gene with four different alleles. How many different types of gametes would be possible in this system?

A)1
B)2
C)4
D)8
E)16

Question 28

In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short?

A)1
B)1/2
C)1/4
D)1/6
E)0

Question 29

Use the following information to answer the questions below.
Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant characteristic.
If True-breeding red long radishes are crossed with True breeding white oval radishes, the F₁ will be expected to be which of the following?

A)Red and long
B)Red and oval
C)White and long
D)Purple and long
E)Purple and oval

Question 30

Use the following information to answer the questions below.
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.
How many genes must be responsible for these coat colors in Labrador retrievers?

A)1
B)2
C)3
D)4

Question 31

In a cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC?

A)1/4
B)1/8
C)1/16
D)1/32
E)1/64

Question 32

The flower color trait in radishes is an example of which of the following?

A)A multiple allelic system
B)Sex linkage
C)Codominance
D)Incomplete dominance
E)Epistasis

Question 33

In snapdragons, heterozygotes for one of the genes have pink flowers, whereas homozygotes have red or white flowers. When plants with red flowers are crossed with plants with white flowers, what proportion of the offspring will have pink flowers?

A)0%
B)25%
C)50%
D)75%
E)100%

Question 34

In cattle, roan coat color (mixed red and white hairs)occurs in the heterozygous (Rr)offspring of red (RR)and white (rr)homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red : 2 roan : 1 white?

A)red × white
B)roan × roan
C)white × roan
D)red × roan
E)The answer cannot be determined from the information provided.

Question 35

Given the parents AABBCc × AabbCc, assume simple dominance and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent?

A)1/4
B)1/8
C)3/4
D)3/8
E)1

Question 36

Use the following information to answer the questions below.
Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant characteristic.
In the F₂ generation of the above cross, which of the following phenotypic ratios would be expected?

A)9:3:3:1
B)9:4:3
C)1:1:1:1
D)1:1:1:1:1:1
E)6:3:3:2:1:1

Question 37

If doubly heterozygous SsNn cactuses were allowed to self-pollinate, the F₂ would segregate in which of the following ratios?

A)3 sharp-spined : 1 spineless
B)1 sharp-spined : 2 dull-spined : 1 spineless
C)1 sharp spined : 1 dull-spined : 1 spineless
D)1 sharp-spined : 1 dull-spined
E)9 sharp-spined : 3 dull-spined : 4 spineless

Question 38

Two True-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F₁ individuals have red, axial flowers. The genes for flower color and location assort independently. If 1,000 F₂ offspring resulted from the cross, approximately how many of them would you expect to have red, terminal flowers?

A)65
B)190
C)250
D)565
E)750

Question 39

Drosophila (fruit flies)usually have long wings (+)but mutations in two different genes can result in bent wings (bt)or vestigial wings (vg). If a homozygous bent wing fly is mated with a homozygous vestigial wing fly, which of the following offspring would you expect?

A)All +bt +vg heterozygotes
B)1/2 bent and 1/2 vestigial flies
C)All homozygous + flies
D)3/4 bent to 1/4 vestigial ratio
E)1/2 bent and vestigial to 1/2 normal

Question 40

A 1:2:1 phenotypic ratio in the F₂ generation of a monohybrid cross is a sign of

A)complete dominance.
B)multiple alleles.
C)incomplete dominance.
D)polygenic inheritance.
E)pleiotropy.

Question 41

The following questions refer to the pedigree chart in Figure 14.2 for a family, some of whose members exhibit the dominant trait, wooly hair. Affected individuals are indicated by an open square or circle.

Figure 14.2
What is the likelihood that the progeny of IV-3 and IV-4 will have wooly hair?

A)0%
B)25%
C)50%
D)75%
E)100%

Question 42

Which describes the ability of a single gene to have multiple phenotypic effects?

A)Incomplete dominance
B)Multiple alleles
C)Pleiotropy
D)Epistasis

Question 43

A blue budgie is crossed with a white budgie. Which of the following results is not possible?

A)Green offspring only
B)Yellow offspring only
C)Blue offspring only
D)Green and yellow offspring
E)a 9:3:3:1 ratio

Question 44

Which of the following terms best describes when the phenotype of the heterozygote differs from the phenotypes of both homozygotes?

A)Incomplete dominance
B)Multiple alleles
C)Pleiotropy
D)Epistasis

Question 45

Which of the following is an example of polygenic inheritance?

A)Pink flowers in snapdragons
B)The ABO blood groups in humans
C)Huntington's disease in humans
D)White and purple flower color in peas
E)Skin pigmentation in humans

Question 46

Which of the following provides an example of epistasis?

A)Recessive genotypes for each of two genes (aabb)results in an albino corn snake.
B)The allele b17 produces a dominant phenotype, although b1 through b16 do not.
C)In rabbits and many other mammals, one genotype (cc)prevents any fur color from developing.
D)In Drosophila (fruit flies), white eyes can be due to an X-linked gene or to a combination of other genes.

Question 47

The following questions refer to the pedigree chart in Figure 14.2 for a family, some of whose members exhibit the dominant trait, wooly hair. Affected individuals are indicated by an open square or circle.

Figure 14.2
What is the probability that individual III-1 is Ww?

A)3/4
B)1/4
C)2/4
D)2/3
E)1

Question 48

Huntington's disease is a dominant condition with late age of onset in humans. If one parent has the disease, what is the probability that his or her child will have the disease?

A)1
B)3/4
C)1/2
D)1/4
E)0

Question 49

Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?

A)Environmental factors such as soil pH
B)The allele for blue hydrangea being completely dominant
C)The alleles being codominant
D)The fact that a mutation has occurred
E)Acknowledging that multiple alleles are involved

Question 50

Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?

A)Incomplete dominance
B)Multiple alleles
C)Pleiotropy
D)Epistasis

Question 51

Use the following information to answer the questions below.
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
Which of the following is a possible phenotype for the father?

A)A negative
B)O negative
C)B positive
D)AB negative
E)Impossible to determine

Question 52

Use the following information to answer the questions below.
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
Which of the following is a possible genotype for the mother?

A)IᴬIᴬ
B)IᴮIᴮ
C)ii
D)Iᴬi
E)IᴬIᴮ

Question 53

Use the following information to answer the questions below.
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
Which of the following is a possible partial genotype for the son?

A)IᴮIᴮ
B)IᴮIA
C)ii
D)Iᴮi
E)IᴬIᴬ

Question 54

Use the following information to answer the questions below.
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
Which of the following is the probable genotype for the mother?

A)IᴬIᴬRR
B)IᴬIᴬRr
C)Iᴬirr
D)IᴬiRr
E)IᴬiRR

Question 55

Which describes the ABO blood group system?

A)Incomplete dominance
B)Multiple alleles
C)Pleiotropy
D)Epistasis

Question 56

Two blue budgies were crossed. Over the years, they produced 22 offspring, 5 of which were white. What are the most likely genotypes for the two blue budgies?

A)yyBB and yyBB
B)yyBB and yyBb
C)yyBb and yyBb
D)yyBB and yybb
E)yyBb and yybb

Question 57

A woman has six sons. The chance that her next child will be a daughter is

A)1)
B)0)
C)1/2.
D)1/6.
E)5/6.

Question 58

Most genes have many more than two alleles. However, which of the following is also True?

A)At least one allele for a gene always produces a dominant phenotype.
B)Most of the alleles will never be found in a live-born organism.
C)All of the alleles but one will produce harmful effects if homozygous.
D)There may still be only two phenotypes for the trait.
E)More than two alleles in a genotype is lethal.

Question 59

The following questions refer to the pedigree chart in Figure 14.2 for a family, some of whose members exhibit the dominant trait, wooly hair. Affected individuals are indicated by an open square or circle.

Figure 14.2
What is the genotype of individual II-5?

A)WW
B)Ww
C)ww
D)WW or ww
E)ww or Ww

Question 60

Use the following information to answer the questions below.
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
If both children are of blood group MM, which of the following is possible?

A)Each parent is either M or MN.
B)Each parent must be type M.
C)Both children are heterozygous for this gene.
D)Neither parent can have the N allele.
E)The MN blood group is recessive to the ABO blood group.

Question 61

A scientist discovers a DNA-based test for the allele of a particular gene. This and only this allele, if homozygous, produces an effect that results in death at or about the time of birth. Of the following, which is the best use of this discovery?

A)To screen all newborns of an at-risk population
B)To design a test for identifying heterozygous carriers of the allele
C)To introduce a normal allele into deficient newborns
D)To follow the segregation of the allele during meiosis
E)To test school-age children for the disorder

Question 62

Phenylketonuria (PKU)is a recessive human disorder in which an individual cannot appropriately metabolize a particular amino acid. This amino acid is not otherwise produced by humans. Therefore the most efficient and effective treatment is which of the following?

A)Feed them the substrate that can be metabolized into this amino acid.
B)Transfuse the patients with blood from unaffected donors.
C)Regulate the diet of the affected persons to severely limit the uptake of the amino acid.
D)Feed the patients the missing enzymes in a regular cycle, i.e., twice per week.

Question 63

An ideal procedure for fetal testing in humans would have which of the following features?

A)Lowest risk procedure that would provide the most reliable information
B)The procedure that can test for the greatest number of traits at once
C)A procedure that provides a 3D image of the fetus
D)The procedure that can be performed at the earliest time in the pregnancy
E)A procedure that could test for the carrier status of the fetus

Question 64

Flower position, stem length, and seed shape were three characters that Mendel studied. Each is controlled by an independently assorting gene and has dominant and recessive expression as follows:
Character Dominant Recessive
Flower position Axial (A) Terminal (a)
Stem length Tall (T) Dwarf (t)
Seed shape Round (R) Wrinkled (r)
If a plant that is heterozygous for all three characters is allowed to self-fertilize, what proportion of the offspring would you expect to be as follows?
(Note: Use the rules of probability instead of a huge Punnett square.)

A)Homozygous for the three dominant traits
B)Homozygous for the three recessive traits
C)Heterozygous for all three characters
D)Homozygous for axial and tall, heterozygous for seed shape

Question 65

One of two major forms of a human condition called neurofibromatosis (NF 1)is inherited as a dominant, although it may be either mildly to very severely expressed. If a young child is the first in her family to be diagnosed, which of the following is the best explanation?

A)The mother carries the gene but does not express it at all.
B)One of the parents has very mild expression of the gene.
C)The condition skipped a generation in the family.
D)The child has a different allele of the gene than the parents.

Question 66

In some plants, a True-breeding, red-flowered strain gives all pink flowers when crossed with a white-flowered strain: CᴿCᴿ (red)× CᵂCᵂ (white)→ CᴿCᵂ (pink). If flower position (axial or terminal)is inherited as it is in peas (see Table 14.1 in your textbook), what will be the ratios of genotypes and phenotypes of the F₁ generation resulting from the following cross: axial-red (True-breeding)× terminal-white?
What will be the ratios in the F₂ generation?

Question 67

A pedigree analysis for a given disorder's occurrence in a family shows that, although both parents of an affected child are normal, each of the parents has had affected relatives with the same condition. The disorder is then which of the following?

A)Recessive
B)Dominant
C)Incompletely dominant
D)Maternally inherited
E)A new mutation

Question 68

The genotype of F₁ individuals in a tetrahybrid cross is AaBbCcDd. Assuming independent assortment of these four genes, what are the probabilities that F₂ offspring will have the following genotypes?

A)aabbccdd
B)AaBbCcDd
C)AABBCCDD
D)AaBBccDd
E)AaBBCCdd

Question 69

An obstetrician knows that one of her patients is a pregnant woman whose fetus is at risk for a serious disorder that is detectable biochemically in fetal cells. The obstetrician would most reasonably offer which of the following procedures to her patient?

A)CVS
B)Ultrasound imaging
C)Amniocentesis
D)Fetoscopy
E)X-ray

Question 70

Cystic fibrosis (CF)is a Mendelian disorder in the human population that is inherited as a recessive. Two normal parents have two children with CF. The probability of their next child being normal for this characteristic is which of the following?

A)0
B)1/2
C)1/4
D)3/4
E)1/8

Question 71

Two pea plants heterozygous for the characters of pod color and pod shape are crossed. Draw a Punnett square to determine the phenotypic ratios of the offspring.

Question 72

Hutchinson-Gilford progeria is an exceedingly rare human genetic disorder in which there is very early senility, and death, usually of coronary artery disease, at an average age of approximately 13. Patients, who look very old even as children, do not live to reproduce. Which of the following represents the most likely assumption?

A)All cases must occur in relatives; therefore, there must be only one mutant allele.
B)Successive generations of a family will continue to have more and more cases over time.
C)The disorder may be due to mutation in a single protein-coding gene.
D)Each patient will have had at least one affected family member in a previous generation.
E)The disease is autosomal dominant.

Question 73

A black guinea pig crossed with an albino guinea pig produces 12 black offspring. When the albino is crossed with a second black one, 7 blacks and 5 albinos are obtained. What is the best explanation for this genetic situation?
Write genotypes for the parents, gametes, and offspring.

Question 74

When a disease is said to have a multifactorial basis, it means that

A)both genetic and environmental factors contribute to the disease.
B)it is caused by a gene with a large number of alleles.
C)it affects a large number of people.
D)it has many different symptoms.
E)it tends to skip a generation.

Question 75

A man with type A blood marries a woman with type B blood. Their child has type O blood. What are the genotypes of these individuals?
What other genotypes, and in what frequencies, would you expect in offspring from this marriage?

Question 76

Phenylketonuria (PKU)is an inherited disease caused by a recessive allele. If a woman and her husband, who are both carriers, have three children, what is the probability of each of the following?

A)All three children are of normal phenotype.
B)One or more of the three children have the disease.
C)All three children have the disease.
D)At least one child is phenotypically normal.
(Note: Remember that the probabilities of all possible outcomes always add up to 1.)

Question 77

The frequency of heterozygosity for the sickle cell anemia allele is unusually high, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following?

A)Mendel's law of independent assortment
B)Mendel's law of segregation
C)Darwin's explanation of natural selection
D)Darwin's observations of competition
E)The malarial parasite changing the allele

Question 78

In sesame plants, the one-pod condition (P)is dominant to the three-pod condition (p), and normal leaf (L)is dominant to wrinkled leaf (l). Pod type and leaf type are inherited independently. Determine the genotypes for the two parents for all possible matings producing the following offspring:

A)318 one-pod, normal leaf and 98 one-pod, wrinkled leaf
B)323 three-pod, normal leaf and 106 three-pod, wrinkled leaf
C)401 one-pod, normal leaf
D)150 one-pod, normal leaf, 147 one-pod, wrinkled leaf, 51 three-pod, normal leaf, and 48 three-pod, wrinkled leaf
E)223 one-pod, normal leaf, 72 one-pod, wrinkled leaf, 76 three-pod, normal leaf, and 27 three-pod, wrinkled leaf

Question 79

People with sickle-cell trait

A)are heterozygous for the sickle-cell allele.
B)are usually healthy.
C)have increased resistance to malaria.
D)produce normal and abnormal hemoglobin.
E)All of the above

Question 80

A man has six fingers on each hand and six toes on each foot. His wife and their daughter have the normal number of digits. Extra digits is a dominant trait. What fraction of this couple's children would be expected to have extra digits?