Deck 14: Mendel and the Gene

Question 1

Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles. Only boys are affected, and they are always born to phenotypically normal parents. Due to the severity of the disease, the boys die in their teens. Is this disorder likely to be caused by a dominant or recessive allele? Is its inheritance sex- linked or autosomal?

A) recessive, sex- linked
B) dominant, autosomal
C) dominant, sex- linked
D) recessive, autosomal

Answer 1

A

Question 2

A black guinea pig crossed with an albino guinea pig produced 12 black offspring. When the albino was crossed with a second black animal, 6 blacks and 6 albinos were obtained. What is the best explanation for this genetic situation?

A) Albino is recessive; black is recessive.
B) Albino and black are codominant.
C) Albino is recessive; black is dominant.
D) Albino is dominant; black is incompletely dominant.
E) None of the above applies.

Answer 2

C

Question 3

Mendel crossed yellow- seeded and green- seeded pea plants and then allowed the offspring to self- pollinate to produce an F₂ generation. The results were as follows: 6022 yellow and 2001 green 8023 total). The allele for green seeds has what relationship to the allele for yellow seeds?

A) incompletely dominant
B) dominant
C) semidominant
D) recessive

Answer 3

D

Question 4

A man and woman are both of normal pigmentation, but both have one parent who is albino without melanin pigmentation). Albinism is an autosomal not sex- linked) recessive trait. What is the probability that their first child will be an albino?

A) 0%
B) 1/8
C) 1/2
D) 1/4
E) 100%

Question 5

Assuming independent assortment for all gene pairs, what is the probability that the following parents, AABbCc
× AaBbCc, will produce an AaBbCc offspring?

A) 9/16
B) 1/8
C) 3/4
D) 1/2
E) 1/16

Question 6

In rabbits, the homozygous CC is normal, Cc results in deformed legs, and cc results in very short legs. The genotype BB produces black fur, Bb brown fur, and bb white fur. If a cross is made between brown rabbits with deformed legs and white rabbits with deformed legs, what percentage of the offspring would be expected to have deformed legs and white fur?

A) 25%
B) 50%
C) 33%
D) 0%
E) 100%

Question 7

Hemophilia is caused by several genetic factors; one, a recessive allele of an X- linked gene, is the subject of this problem. Assume that a man with hemophilia marries a normal woman whose father had hemophilia. What is the probability that they will have a daughter with hemophilia?

A) 1/8
B) 1/16
C) 3/4
D) 1/2
E) 1/4

Question 8

Phenylketonuria is an inherited disease caused by a recessive autosomal allele. If a woman and her husband are both carriers, what is the probability that their first child will be a phenotypically normal girl?

A) 1.0
B) 3/8
C) 3/16
D) 1/4
E) 1/16

Question 9

In Drosophila melanogaster, vestigial short) wings vg) are caused by a recessive allele of a gene that independently assorts with a gene pair that influences body hair. Hairy h) results in a hairy body. A cross is made between a fly with normal wings and a hairy body and a fly with vestigial wings and a normal body. The phenotypically normal F₁ flies were crossed among each other, and 1024 F₂ flies were reared. What phenotypes would you expect in the F₂, and in what actual numbers not ratios) would you expect to find them?

A) phenotypes-wild, vestigial, hairy, vestigial hairy; numbers expected-wild 256), vestigial 256), hairy 256), vestigial hairy 256)
B) phenotypes-hairy, vestigial hairy; numbers expected-hairy 512), vestigial hairy 512)
C) phenotypes-wild, vestigial; numbers expected-wild 576), vestigial 576)
D) phenotypes-all wild; numbers expected-wild 1024)
E) phenotypes-wild, vestigial, hairy, vestigial hairy; numbers expected-wild 576), vestigial 192), hairy 192), vestigial hairy 64)

Question 10

Suppose two AaBbCc individuals are mated. Assuming that the genes are not linked, what fraction of the offspring are expected to be homozygous recessive for the three traits?

A) 1/8
B) 1/256
C) 1/64
D) 1/4
E) 1/16

Question 11

A man has extra digits six fingers on each hand and six toes on each foot). His wife and their daughter have a normal number of digits. Having extra digits is a dominant trait. The couple's second child has extra digits. What is the probability that their next third) child will have extra digits?

A) 9/16
B) 3/4
C) 1/16
D) 1/2
E) 1/8

Question 12

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

Question 13

A heterozygous, but phenotypically wild- type fruit fly gray body colour and normal wings) was mated to a black fly with vestigial wings. The offspring had the following phenotypic distribution: wild type, 720;
Black- vestigial, 780; black- normal, 280; gray- vestigial, 220. What conclusion is likely from these results?

A) Epistasis has modified a 9:3:3:1 ratio.
B) The black and vestigial loci are linked.
C) The black and vestigial loci are allelic.
D) The black and vestigial loci assort independently from each other.

Question 14

When Mendel crossed yellow- seeded and green- seeded pea plants, all the offspring were yellow seeded. When he took these F₁ yellow- seeded plants and crossed them to green- seeded plants, what genotypic ratio is expected?

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

Question 15

Different ratios occur in crosses with single gene pairs or two gene pairs. What types of ratios are likely to occur in crosses dealing with a single gene pair?

A) 3:1, 1:1, 1:2:1
B) 9:7, 12:3:1
C) 1:1:1:1, 1:4:6:4:1
D) 9:3:3:1, 1:2:1
E) 15:1, 1:2

Question 16

A recessive allele on the X chromosome is responsible for red- green colour blindness in humans. A woman with normal vision whose father is colour blind marries a colour- blind male. What is the probability that this couple's first son will be colour blind?

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

Question 17

A man and woman are both of normal pigmentation and have a child who is albino without melanin pigmentation). Albinism is an autosomal not sex- linked) recessive trait. What are the genotypes of the albino's parents?

A) Both parents must be homozygous dominant.
B) Both parents must be heterozygous.
C) One parent must be heterozygous, the other parent can be homozygous dominant, homozygous recessive, or heterozygous.
D) One parent must be homozygous dominant; the other parent must be heterozygous.
E) One parent must be homozygous for the recessive allele, the other parent can be homozygous dominant, homozygous recessive, or heterozygous.

Question 18

Gray seed colour in peas is dominant to white. Assume that Mendel conducted a series of experiments where plants with gray seeds were crossed among themselves, and the following progeny were produced: 302 gray and 98 white. a) What is the most probable genotype of each parent? b) Based on your answer in a) above, what genotypic and phenotypic ratios are expected in these progeny? Assume the following symbols: G = gray and g = white.)

A) a) gg × Gg; b) genotypic = 1:2, phenotypic = 3:1
B) a) GG × Gg; b) genotypic = 1:2:1, phenotypic = 2:1
C) a) GG × gg; b) genotypic = 3:1, phenotypic = 1:2:1
D) a) Gg × Gg; b) genotypic = 3:1, phenotypic = 9:3:3:1
E) a) Gg × Gg; b) genotypic = 1:2:1, phenotypic = 3:1

Question 19

A man and woman are both of normal pigmentation, but both have one parent who is albino without melanin pigmentation). Albinism is an autosomal not sex- linked) recessive trait. What is the probability that their first female child will have albinism?

A) 0%
B) 1/8
C) 1/2
D) 1/4
E) 100%

Question 20

In tigers, a recessive allele causes a white tiger absence of fur pigmentation). If two phenotypically normal tigers that are heterozygous at this locus are mated, what percentage of their offspring is expected to be white?

A) 50%
B) 75%
C) about 90%
D) 25%
E) about 66%

Question 21

Glucose- 6- phosphate dehydrogenase deficiency G6PD) is inherited as a recessive allele of an X- linked gene in humans. A woman whose father suffered from G6PD marries a normal man. a) What proportion of their sons is expected to be G6PD? b) If the husband was not normal but was G6PD deficient, would you change your answer in part a)?

A) a) zero; b) no
B) a) 1/2; b) no
C) a) 1/2; b) yes
D) a) 2/3; b) no
E) a) 100%; b) no

Question 22

In humans, blue eyes are inherited as a recessive autosomal trait and colour blindness is an X- linked recessive trait. A woman with blue eyes and normal colour vision whose father was colour blind marries a man who also has normal colour vision. He has brown eyes but his mother had blue eyes. Which of the following do you expect to be true for their daughters?

A) Their daughters will all have normal colour vision and blue eyes.
B) One- half of their daughters will be colour blind and have blue eyes; 1/2 their daughters will be colour blind and have brown eyes.
C) Their daughters will all have normal colour vision and brown eyes.
D) One- half of their daughters will have normal colour vision and brown eyes; 1/2 of their daughters will have normal colour vision and blue eyes.
E) One- fourth of their daughters will be colour blind and have blue eyes, 1/4 of their daughters will be colour blind and have brown eyes, 1/4 of their daughters will have normal colour vision and blue eyes, 1/4 of their daughters will have normal colour vision and brown eyes.

Question 23

Regarding an allelic pair for flower colour in snapdragons, heterozygotes have pink flowers, whereas the two homozygotes have red flowers or white flowers. When plants with red flowers are crossed with plants with white flowers, what proportion of the offspring is expected to have pink flowers?

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

Question 24

The second child of the couple above is unaffected does not display the condition). What is the probability this child is a carrier for the ataxia condition?

A) 0
B) 1/2
C) 2/3
D) 1/4
E) 1/16

Question 25

Whenever the dominant allele of either or both) gene A or gene B is present, red colour is produced. A cross of
AaBb × AaBb can be expected to yield how many red offspring out of 16? Assume the genes are not linked.

A) 1
B) 4
C) 12
D) 15
E) 16

Question 26

A couple has a child with Harman's ataxia a recessive disorder). If this couple has second child, what is the probability that child will have ataxia?

A) 2/3
B) 0
C) 1/2
D) 1/16
E) 1/4

Question 27

$\begin{array} { c c c } \text { Sex } & \text { Phenotype } & \text { Number } \\\text { male } & \text { wild } & 123 \\\text { male } & \text { yellow } & 116 \\\text { female } & \text { wild } & 240\end{array}$ Figure 14.1

-In a Drosophila experiment, a cross was made between homozygous wild- type females and yellow- bodied males. All of the resulting F₁s were phenotypically wild type. However, adult flies of the F₂ generation resulting from matings of the F₁s) had the characteristics shown in the figure above:
A. Is the mutant allele for yellow body recessive or dominant?
B. Is the yellow locus autosomal not X- linked) or X- linked?

A) a) recessive; b) not X- linked
B) a) dominant; b) not X- linked
C) a) dominant; b) X- linked
D) a) recessive; b) X- linked
E) none of the above

Question 28

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 trait. 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) purple and oval
C) purple and long
D) red and oval
E) white and long

Question 29

Snapdragons are flowers that come in a variety of colours, including red, pink, and white. A series of crosses wit snapdragons having flowers of different colours produced the following results:
Pink × pink: 27 pink, 13 red, 14 white red × red: all red
White × white: all white
Pink × white: 29 pink, 26 white pink × red: 28 pink, 27 red white × red: all pink
Based on the results, what is the most reasonable explanation for the inheritance of these flower colours?

A) qualitative effects
B) pleiotropic effects
C) incomplete dominance
D) codominance
E) more than two alleles

Question 30

What is the probability that a gamete from an individual with the genotype E₁E₂X₁X₁A₁A₂M₂M₂ will contain all paternally derived homologues?

A) 1/6
B) 1/16
C) 1/4
D) 1/8

Question 31

Hemophilia is caused by several genetic factors; one, a recessive allele of an X- linked gene, is the subject of this problem. Assume that a man with hemophilia marries a normal woman whose father had hemophilia. What is the probability that their first son will have hemophilia?

A) 1/2
B) 1/4
C) 3/4
D) 1/16
E) 1/8

Question 32

In humans, blue eyes are inherited as a recessive autosomal trait and colour blindness is an X- linked recessive trait. A woman with blue eyes and normal colour vision whose father was colour blind marries a man who also has normal colour vision. He has brown eyes, but his mother had blue eyes. Which of the following do you expect to be true for their sons?

A) Their sons will all have normal colour vision and brown eyes.
B) Their sons will all have normal colour vision and blue eyes.
C) One- half of their sons will have normal colour vision and brown eyes; 1/2 of their sons will have normal colour vision and blue eyes.
D) One- fourth of their sons will be colour blind and have blue eyes, 1/4 of their sons will be colour blind and have brown eyes, 1/4 of their sons will have normal colour vision and blue eyes, 1/4 of their sons will have normal colour vision and brown eyes.
E) One- half of their sons will be colour blind and have blue eyes; 1/2 their sons will be colour blind and have brown eyes.

Question 33

The B- globin gene has many alleles. What is the maximum number of different alleles of the B- globin gene that could be carried by 6 children with the same mom and dad given that the parents are heterozygous?

A) 6
B) 12
C) 8
D) 4

Question 34

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. A cross between a true- breeding sharp- spined cactus and a spineless cactus would produce

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

Question 35

Two individuals of genotype AABBCCDD and aabbccdd are mated. The F1 generation is interbred self- fertilized) to yield 5000 progeny. What proportion of the F2 is expected to be AabbCcDD?

A) 1/2
B) 1/78
C) 1/64
D) 1/8

Question 36

A man who carries an allele of an X- linked gene will pass it on to

A) half of his sons.
B) all of his sons.
C) all of his children.
D) all of his daughters.
E) half of his daughters.

Question 37

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. 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:1 dull- spined
C) 9 sharp- spined:3 dull- spined:4 spineless
D) 1 sharp- spined:1dull- spined:1 spineless
E) 1 sharp- spined:2 dull- spined:1 spineless

Question 38

Figure 14.3
The distance between two genes is a determinant of their recombination frequency. Based on the image below, which of the following sets of genes will show the greatest recombination frequency?

A) A and B
B) C and D
C) A and E
D) B and C

Question 39

A homozygous tomato plant with red fruit and yellow flowers was crossed with a homozygous tomato plant with golden fruit and white flowers. The F₁ all had red fruit and yellow flowers. The following phenotypes were obtained in the F₂:
Red fruit and yellow flowers-41 Red fruit and white flowers-7 Golden fruit and yellow flowers-8 Golden fruit and white flowers-44
How many map units separate these genes?

A) 15
B) 17.6
C) 35
D) 18.1
E) 17.1

Question 40

There are 40 different alleles for a gene involved in immune function. What is the maximum number of alleles that a human can have?

A) 1
B) 20
C) 2
D) 40
E) 80

Question 41

What is the likelihood that the progeny of IV- 3 and IV- 4 will have the trait?

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

Question 42

Julie has Harman's ataxia hh) and also has achrondoplasia Aa). Josh is a carrier for Harman's ataxia, an autosomal recessive disorder, and has achondroplasia Aa), which is an autosomal dominant trait. AA human embryos do not survive beyond the first few cell divisions. What is the probability that a child born to them would have only Harman's ataxia? Assume the genes are unlinked.

A) 0
B) 1/4
C) 1/12
D) 1/16
E) 1/6

Question 43

In humans, ABO blood types refer to glyocproteins in the membranes of red blood cells. There are three alleles for this autosomal gene: IA, IB, and i. The IA allele codes for the A glycoprotein, the IB allele codes for the B glycoprotein, and the i allele doesn't code for any membrane glycoprotein. IA and IB are codominant, and i is recessive to both IA and IB. People with A type blood have the genotypes IAIA or IAi, people with type B blood are IBIB or IBi, people with type AB blood are IAIB, and people with O type blood are ii. If a woman with type AB blood marries a man with type O blood, which of the following blood types could their children possibly have?

A) A and B
B) AB and O
C) A, B, and O
D) A, B, and AB
E) A, B, AB, and O

Question 44

The figure provided shows the pedigree for a family. Dark- shaded symbols represent individuals with one of the two major types of colon cancer. Numbers under the symbols are the individual's age at the time of diagnosis. Males are represented by squares, females by circles.

From this pedigree, this trait seems to be inherited

A) from mothers.
B) as an autosomal dominant.
C) as an autosomal recessive.
D) as a result of epistasis.
E) as an incomplete dominant.

Question 45

A man is heterozygous for two genes R and L) that are located on different chromosomes. Which of the following processes would result in different combinations of the alleles for these two genes in his sperm?

A) recombination
B) fertilization
C) independent assortment
D) sister chromatid segregation

Question 46

The following questions) refer to the pedigree chart in the figure provided for a family, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle.

What is the genotype of individual II- 5?

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

Question 47

Figure 14.2
In the figure above, flower A was crossed with flower B to produce flower C. The phenotype of flower C is the result of

A) aneuploidy.
B) codominance.
C) the passing on of a sex- linked trait.
D) incomplete dominance.