Deck 5: Extensions and Modifications of Basic Principles

Question 1

You are studying body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown), b^r (red), b^g (green), and b^y (yellow). B is dominant to all the other alleles, and b^y is recessive to all the other alleles. The b^g allele is dominant to b^y but recessive to b^r. You cross a pure-breeding brown spider with a pure-breeding green spider.

-Predict the genotype of the progeny.

A) B/b^g
B) B^r/b^g
C) b^r/b^y
D) b^y/b^g
E) B/b^y

Answer 1

B/b^g

Question 2

You are studying body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown), b^r (red), b^g (green), and b^y (yellow). B is dominant to all the other alleles, and b^y is recessive to all the other alleles. The b^g allele is dominant to b^y but recessive to b^r. You cross a pure-breeding brown spider with a pure-breeding green spider.

-Predict the phenotype of the progeny.

A) half brown, half green
B) three-fourths brown, one-fourth green
C) all brown
D) all green
E) all yellow

Answer 2

all brown

Question 3

Interactions among the human ABO blood group alleles involve _____ and _____.

A) codominance; complete dominance
B) codominance; incomplete dominance
C) complete dominance; incomplete dominance
D) epistasis; complementation
E) continuous variation; environmental variation

Answer 3

A

Question 4

Suppose that extra fingers and toes are caused by a recessive trait, but it appears in only 60% of homozygous recessive individuals. Two heterozygotes conceive a child. What is the probability that this child will have extra fingers and toes?

A) 0.05
B) 0.10
C) 0.15
D) 0.25
E) 0.33

Question 5

In the endangered African watchamakallit, the offspring of a true-breeding black parent and a true-breeding white parent are all gray. When the gray offspring are crossed among themselves, their offspring occur in a ratio of 1 black : 2 gray : 1 white. Upon close examination of the coats, each hair of a gray animal is gray. What is the mode of inheritance?

A) one gene pair with black dominant to white
B) one gene pair with codominance
C) one gene pair with incomplete dominance
D) two gene pairs with recessive epistasis
E) two gene pairs with duplicate genes

Question 6

A mother with blood type B has a child with blood type O. Give all possible blood types for the father of this child.

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

Question 7

In rabbits, an allelic series helps to determine coat color: C (full color), c^ch (chinchilla; gray color), c^h (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, c^ch is dominant to c^h and c, c^h is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > c^ch > c^h > c.

-Indicate the phenotypic ratios expected of rabbits with the cross Cc × c^hc.

A) 1 full color : 1 chinchilla
B) 1 full color : 1 Himalayan
C) 1 chinchilla : 1 Himalayan
D) 3 full color : 1 chinchilla
E) 2 full color : 1 Himalayan : 1 albino

Question 8

Achondroplasia is a common cause of dwarfism in humans. All individuals with achondroplasia are thought to be heterozygous at the locus that controls this trait. When two individuals with achondroplasia mate, the offspring occur in a ratio of 2 achondroplasia : 1 normal. What is the MOST likely explanation for these observations?

A) Achondroplasia is incompletely dominant to the normal condition.
B) Achondroplasia is codominant to the normal condition.
C) The allele that causes achondroplasia is a dominant lethal allele.
D) The allele that causes achondroplasia is a recessive lethal allele.
E) The allele that causes achondroplasia is a late-onset lethal allele.

Question 9

In rabbits, an allelic series helps to determine coat color: C (full color), c^ch (chinchilla; gray color), c^h (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, c^ch is dominant to c^h and c, c^h is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > c^ch > c^h > c.

-Indicate the phenotypic ratios expected of rabbits with the cross Cc^h × c^hc.

A) 1 full color : 1 chinchilla
B) 1 full color : 1 Himalayan
C) 1 chinchilla : 1 Himalayan
D) 3 full color : 1 chinchilla
E) 2 full color : 1 Himalayan : 1 albino

Question 10

Crossing two yellow mice results in 2/3 yellow offspring and 1/3 nonyellow offspring. What percentage of offspring would you expect to be nonyellow if you crossed two nonyellow mice?

A) 25%
B) 33%
C) 66%
D) 75%
E) 100%

Question 11

Polydactyly is the condition of having extra fingers or toes. Some polydactylous persons possess extra fingers or toes that are fully functional, whereas others possess only a small tag of extra skin. This is an example of:

A) variable expressivity.
B) complete dominance.
C) independent assortment.
D) complementation.
E) cytoplasmic inheritance.

Question 12

The R locus determines flower color in a new plant species. Plants that are genotype RR have red flowers, and plants that are rr have white flowers. However, Rr plants have pink flowers. What type of inheritance does this demonstrate for flower color in these plants?

A) complete dominance
B) incomplete dominance
C) codominance
D) complementation
E) lethal alleles

Question 13

A mother with blood type AB has a child with blood type B. Give all possible blood types for the father of this child.

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

Question 14

In rabbits, an allelic series helps to determine coat color: C (full color), c^ch (chinchilla; gray color), c^h (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, c^ch is dominant to c^h and c, c^h is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > c^ch > c^h > c.

-Indicate the phenotypic ratios expected of rabbits with the cross Cc^ch × Cc^h.

A) 1 full color : 1 chinchilla
B) 1 full color : 1 Himalayan
C) 1 chinchilla : 1 Himalayan
D) 3 full color : 1 chinchilla
E) 2 full color : 1 Himalayan : 1 albino

Question 15

A mother with blood type A has a child with blood type A. Give all possible blood types for the father of this child.

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

Question 16

In rabbits, an allelic series helps to determine coat color: C (full color), c^ch (chinchilla; gray color), c^h (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, c^ch is dominant to c^h and c, c^h is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > c^ch > c^h > c.

- Indicate the phenotypic ratios expected of rabbits with the cross Cc^h × cc.

A) 1 full color : 1 chinchilla
B) 1 full color : 1 Himalayan
C) 1 chinchilla : 1 Himalayan
D) 3 full color : 1 chinchilla
E) 2 full color :1 Himalayan : 1 albino

Question 17

In humans, blood types A and B are codominant to each other and each is dominant to O. What blood types are possible among the offspring of a couple of blood types AB and A?

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

Question 18

A mother of blood type A gives birth to a child with blood type O. Which of the following could NOT be the blood type of the father?

A) A
B) B
C) O
D) AB
E) Any of these is a possible blood type of the father.

Question 19

A mother with blood type A has a child with blood type AB. Give all possible blood types for the father of this child.

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

Question 20

In rabbits, an allelic series helps to determine coat color: C (full color), c^ch (chinchilla; gray color), c^h (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, c^ch is dominant to c^h and c, c^h is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > c^ch > c^h > c.

- Indicate the phenotypic ratios expected of rabbits with the cross c^chc^h × c^hc.

A) 1 full color : 1 chinchilla
B) 1 full color : 1 Himalayan
C) 1 chinchilla : 1 Himalayan
D) 3 full color : 1 chinchilla
E) 2 full color : 1 Himalayan : 1 albino

Question 21

In purple people eaters, purple is dominant to white. A true-breeding white mutant is mated with a different true-breeding white mutant. All of the F₁ are purple. When the purple F₁ offspring mate with each other, their offspring occur in the ratio of 9 purple : 7 white. Which phenomenon explains the purple F₁ offspring?

A) recessive epistasis
B) dominant epistasis
C) complementation
D) mutation
E) suppression

Question 22

Coat color is determined by two loci, A and B, in large cats. Two pink panthers fall in love and produce a large litter of baby panthers with the following phenotypic ratios: 12/16 pink; 3/16 black; and 1/16 white.

-What is the genotype of the black progeny?

A) A_ B_
B) A_ BB
C) aa B_
D) aa bb
E) A_ B_ and A_ bb

Question 23

Coat color is determined by two loci in large cats. Two pink panthers fall in love and produce a large litter of baby panthers with the following phenotypic ratios: 12/16 pink; 3/16 black; and 1/16 white.

-What kind of gene interaction is this?

A) recessive epistasis
B) dominant epistasis
C) duplicate recessive epistasis
D) duplicate dominant epistasis
E) dominant and recessive epistasis

Question 24

Two loci control body color in beetles. In a cross between a black beetle and a white beetle you obtain a ratio of 9 black to 7 white beetles. What kind of gene interaction is this?

A) recessive epistasis
B) dominant epistasis
C) duplicate recessive epistasis
D) duplicate dominant epistasis
E) dominant and recessive epistasis

Question 25

Hair color is determined in Labrador retrievers by alleles at the B and E loci. A dominant allele B encodes black pigment, whereas a recessive allele b encodes brown pigment. Alleles at a second locus affect the deposition of the pigment in the shaft of the hair; dominant allele E allows dark pigment (black or brown) to be deposited, whereas recessive allele e prevents the deposition of dark pigment, causing the hair to be yellow.

- A black female Labrador retriever was mated with a yellow male. Half of the puppies were black and half were yellow. If the genotype of the black female parent was Bb Ee, then what was the genotype of the other parent?

A) bb ee
B) bb EE
C) Bb ee
D) BB ee
E) BB EE

Question 26

Coat color is determined by two loci, A and B, in large cats. Two pink panthers fall in love and produce a large litter of baby panthers with the following phenotypic ratios: 12/16 pink; 3/16 black; and 1/16 white.

-What is the genotype of the pink progeny?

A) A_ B_
B) A_ bb
C) aa B_
D) aa bb
E) A_ B_ and A_ bb

Question 27

Describe the differences between dominance, codominance, and incomplete dominance.

Question 28

Coat color is determined by two loci, A and B, in large cats. Two pink panthers fall in love and produce a large litter of baby panthers with the following phenotypic ratios: 12/16 pink; 3/16 black; and 1/16 white.

- What is the genotype of the white progeny?

A) A_ B_
B) A_ bb
C) aa B_
D) aa bb
E) A_ B_ and A_ bb

Question 29

In the Mexican Hairless breed of dog, the hairless condition is produced by the heterozygous genotype (Hh). Normal dogs are homozygous recessive (hh). Puppies homozygous for the H allele are usually born dead. If the average litter size at weaning (after nursing) is six puppies in matings between hairless dogs, what would be the average expected number (not a ratio) of hairless and normal offspring at weaning from matings between hairless and normal dogs?

A) 6 normal dogs and 2 hairless dogs
B) 2 normal dogs and 1 hairless dog
C) 5 normal dogs and 1 hairless dog
D) 3 normal dogs and 3 hairless dogs
E) 4 normal dogs and 4 hairless dogs

Question 30

In order to determine if mutations from different organisms in the same species that exhibit the same phenotype are allelic, which test would you perform?

A) testcross
B) epistasis test
C) complementation test
D) allelic series test
E) biochemical test

Question 31

How does epistasis differ from Mendel's principle of dominance?

Question 32

Suppose that the "fabulous" phenotype is controlled by two genes, A and B, as shown in the following diagram. Allele A produces enough enzyme 1 to convert "plain" to "smashing." Allele a produces no enzyme 1. Allele B produces enough enzyme 2 to convert "smashing" to "fabulous." Allele b produces no enzyme 2. The A and B genes are both autosomal and assort independently.

- What will be the phenotype(s) of the F₂ offspring of a true-breeding "fabulous" father and a true-breeding "plain" mother (aa bb)?

A) 9 "fabulous" : 7 "plain"
B) 13 "fabulous" : 3 "plain"
C) 9 "fabulous" : 3 "smashing" : 4 "plain"
D) 12 "plain" : 3 "fabulous" : 1 "smashing"
E) 15 "fabulous" : 1 "smashing"

Question 33

Suppose that the "fabulous" phenotype is controlled by two genes, A and B, as shown in the following diagram. Allele A produces enough enzyme 1 to convert "plain" to "smashing." Allele a produces no enzyme 1. Allele B produces enough enzyme 2 to convert "smashing" to "fabulous." Allele b produces no enzyme 2. The A and B genes are both autosomal and assort independently.

- What will be the phenotype(s) of the F₁ offspring of a true-breeding "fabulous" father and a true-breeding "plain" mother (aa bb)?

A) all "plain"
B) all "smashing"
C) all "fabulous"
D) "plain" females and "fabulous" males
E) "fabulous" females and "smashing" males

Question 34

Hair color is determined in Labrador retrievers by alleles at the B and E loci. A dominant allele B encodes black pigment, whereas a recessive allele b encodes brown pigment. Alleles at a second locus affect the deposition of the pigment in the shaft of the hair; dominant allele E allows dark pigment (black or brown) to be deposited, whereas recessive allele e prevents the deposition of dark pigment, causing the hair to be yellow.

-What type of gene interaction does this represent?

A) recessive epistasis
B) dominant epistasis
C) duplicate recessive epistasis
D) duplicate dominant epistasis
E) dominant and recessive epistasis

Question 35

A man is heterozygous for a rare trait that is assumed to be caused by a dominant autosomal mutant allele. He marries a woman who is phenotypically normal. They have a phenotypically normal daughter who marries a phenotypically normal man. Unexpectedly their first child, a girl, has the same abnormal trait as her grandfather. Which of the following BEST explains this situation?

A) The trait is really due a mutation in a cytoplasmic gene and can be only inherited from the mother.
B) This is a sex-influenced trait and is expressed more often in females than in males.
C) This is an example of genomic imprinting and the mutant allele is only expressed if it is inherited from the father.
D) The mutant allele shows incomplete dominance when heterozygous with the normal allele.
E) The mutant allele shows reduced penetrance and the normal daughter carries the mutant allele.

Question 36

You are studying a gene that controls ossicone (horn) length in giraffes. The wild-type long-ossicone allele (L) is dominant to the mutant short-ossicone (l) allele. However, the L allele is only 60% penetrant. You cross two heterozygous giraffes. What proportion of offspring would you expect to exhibit the short-ossicone phenotype? Assume the penetrance of L applies equally to both homozygotes and heterozygotes.

A) 0.25
B) 0.40
C) 0.45
D) 0.55
E) 0.60

Question 37

How do incomplete penetrance and variable expressivity differ?

Question 38

A geneticist is examining a culture of fruit flies and discovers a single female with strange spots on her legs. The new mutation is named melanotic. When a female melanotic fly is crossed with a normal male, the following progeny are produced: 123 normal females, 125 melanotic females, and 124 normal males. In subsequent crosses with normal males, melanotic females are frequently obtained but never any melanotic males. Provide a possible explanation for the inheritance of the melanotic mutation. (Hint: The cross produces twice as many female progeny as male progeny.)

Question 39

You are studying a gene that controls ossicone (horn) length in giraffes. The wild-type long-ossicone allele (L) is dominant to the mutant short-ossicone (l) allele. However, the L allele is only 60% penetrant. You cross two heterozygous giraffes. What proportion of offspring would you expect to exhibit the long-ossicone phenotype? Assume the penetrance of L applies equally to both homozygotes and heterozygotes.

A) 0.40
B) 0.45
C) 0.55
D) 0.60
E) 0.75

Question 40

How do incomplete dominance and codominance differ?

Question 41

A homozygous strain of corn that produces yellow kernels is crossed with another homozygous strain that produces purple kernels. When the F₁ are interbred, 280 of the F₂ are yellow and 70 are purple.

A) If kernel color is controlled by a single gene pair with yellow dominant to purple, what would be the expected ratio of yellow to purple in the F₂?
B) Do the observed data differ significantly from that expected in (a)? Explain your answer.
C) Provide an alternative explanation for the inheritance of kernel color and evaluate it by comparing the observed data to that expected from your alternative hypothesis.

Question 42

In a certain species of plant, flowers occur in three colors: blue, pink, and white. A pure-breeding pink plant is mated with a pure-breeding white plant. All of the F₁ are blue. When the blue F₁ plants are selfed, the F₂ plants occur in the ratio 9 blue : 3 pink : 4 white. The genotype that produces white is ww. The presence of one W allele allows pink or blue color to occur. The alleles at the hypostatic locus are B (blue) and b (pink).

- What is the genotype of the F₁ plants?

A) bb WW
B) bb Ww
C) Bb Ww
D) Bb ww
E) BB ww

Question 43

The presence of a beard on some goats is determined by an autosomal gene that is dominant in males and recessive in females. Heterozygous males are bearded, while heterozygous females are beardless. What type of inheritance is exhibited by this trait?

A) sex-linked
B) sex-limited
C) sex-influenced
D) autosomal recessive
E) autosomal dominant

Question 44

In chickens, comb shape is determined by genes at two loci (R, r and P, p). A walnut comb is produced when at least one dominant gene R is present at one locus and at least one dominant gene P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant gene is present at the first locus and two recessive genes are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive genes are present at the first locus and at least one dominant gene is present at the second (genotype rr P_). If two recessive genes are present at the first and the second locus (rr pp), a single comb is produced.

-Give genotypes for comb shape of the parents in the following cross: Rose crossed with walnut produces 6 walnut, 6 rose, 2 single, and 2 pea offspring.

A) RR pp × rr PP
B) Rr pp × rr Pp
C) Rr pp × rr PP
D) RR pp × rr Pp
E) Rr pp × Rr Pp

Question 45

Deafness is often inherited in humans as an autosomal recessive trait. Assume that this is the case here. Two severely deaf people meet and marry. They have four children and all of them have normal hearing. What is the MOST reasonable explanation for this outcome?

A) The mutant allele for deafness shows variable expressivity and the normal children may have some hearing loss that is difficult to detect.
B) Complementation has occurred in the children, indicating that the deafness mutations in the parents involved different genes.
C) Deafness in this family shows a genetic maternal effect with the condition being determined by the genotype of the mother.
D) Deafness in this family is most likely caused by an epigenetic change such as the addition of methyl groups to the DNA.
E) The mutant allele for deafness shows anticipation and becomes more weakly expressed in succeeding generations.

Question 46

In chickens, comb shape is determined by genes at two loci (R, r and P, p). A walnut comb is produced when at least one dominant gene R is present at one locus and at least one dominant gene P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant gene is present at the first locus and two recessive genes are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive genes are present at the first locus and at least one dominant gene is present at the second (genotype rr P_). If two recessive genes are present at the first and the second locus (rr pp), a single comb is produced.

- Give genotypes for comb shape of the parents in the following cross: Rose crossed with single produces 10 rose and 11 single offspring.

A) RR PP × rr pp
B) RR Pp × rr pp
C) Rr PP × rr pp
D) Rr Pp × rr pp
E) Rr pp × rr pp

Question 47

In the yawncat (a rare hypothetical animal), the dominant allele R causes solid tail color, and the recessive allele r results in white spots on a colored background. The black coat color allele B is dominant to the brown allele b, but the B and b alleles can only be expressed if the animal has an mm genotype at a third gene locus. Animals that are M_ are yellow regardless of which allele from the B locus is present. A mating between a solid yellow-tailed male yawncat and a solid brown-tailed female yawncat produces 16 offspring with the following tail phenotypes: six solid yellow, two spotted yellow, three solid black, one spotted black, three solid brown, and one spotted brown.

- What is the probability of the next offspring from these same two parents having a spotted brown tail?

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

Question 48

What is a dominant epistatic gene?

Question 49

In chickens, comb shape is determined by genes at two loci (R, r and P, p). A walnut comb is produced when at least one dominant gene R is present at one locus and at least one dominant gene P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant gene is present at the first locus and two recessive genes are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive genes are present at the first locus and at least one dominant gene is present at the second (genotype rr P_). If two recessive genes are present at the first and the second locus (rr pp), a single comb is produced.

-Give genotypes for comb shape of the parents in the following cross: Pea crossed with single produces 1 single offspring.

A) rr PP × rr pp
B) RR Pp × rr pp
C) Rr PP × rr pp
D) Rr Pp × rr pp
E) rr Pp × rr pp

Question 50

A yeast geneticist isolates two different haploid mutant yeast strains, strain A and strain B, which cannot grow unless the amino acid leucine is added to the growth media. Wild-type yeast strains can make their own leucine and do not require that it be added to the growth media. The geneticist discovers that each mutant yeast strain contains a single recessive mutation that leads to the observed leucine-requiring phenotype. When she crosses the two mutant strains together, she observes that the resulting diploid can grow without leucine added to the growth media. Explain the allelic relationship between the mutations in these two strains.

Question 51

In the yawncat (a rare hypothetical animal), the dominant allele R causes solid tail color, and the recessive allele r results in white spots on a colored background. The black coat color allele B is dominant to the brown allele b, but the B and b alleles can only be expressed if the animal has an mm genotype at a third gene locus. Animals that are M_ are yellow regardless of which allele from the B locus is present. A mating between a solid yellow-tailed male yawncat and a solid brown-tailed female yawncat produces 16 offspring with the following tail phenotypes: six solid yellow, two spotted yellow, three solid black, one spotted black, three solid brown, and one spotted brown.

- What is the MOST likely genotype of the male parent?

A) MM BB RR
B) MM Bb RR
C) Mm Bb RR
D) Mm BB Rr
E) Mm Bb Rr

Question 52

In a certain species of plant, flowers occur in three colors: blue, pink, and white. A pure-breeding pink plant is mated with a pure-breeding white plant. All of the F₁ are blue. When the blue F₁ plants are selfed, the F₂ plants occur in the ratio 9 blue : 3 pink : 4 white. The genotype that produces white is ww. The presence of one W allele allows pink or blue color to occur. The alleles at the hypostatic locus are B (blue) and b (pink).

- What is the genotype of the white parent?

A) bb WW
B) bb Ww
C) Bb Ww
D) Bb ww
E) BB ww

Question 53

In the yawncat (a rare hypothetical animal), the dominant allele R causes solid tail color, and the recessive allele r results in white spots on a colored background. The black coat color allele B is dominant to the brown allele b, but the B and b alleles can only be expressed if the animal has an mm genotype at a third gene locus. Animals that are M_ are yellow regardless of which allele from the B locus is present. A mating between a solid yellow-tailed male yawncat and a solid brown-tailed female yawncat produces 16 offspring with the following tail phenotypes: six solid yellow, two spotted yellow, three solid black, one spotted black, three solid brown, and one spotted brown.

-What is the MOST likely genotype of the female parent?

A) mm bb rr
B) Mm bb rr
C) mm Bb rr
D) mm bb Rr
E) mm Bb Rr

Question 54

In chickens, comb shape is determined by genes at two loci (R, r and P, p). A walnut comb is produced when at least one dominant gene R is present at one locus and at least one dominant gene P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant gene is present at the first locus and two recessive genes are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive genes are present at the first locus and at least one dominant gene is present at the second (genotype rr P_). If two recessive genes are present at the first and the second locus (rr pp), a single comb is produced.

-Give genotypes for comb shape of the parents in the following cross: Rose crossed with pea produces 20 walnut offspring.

A) RR pp × rr PP
B) Rr pp × rr Pp
C) Rr pp × rr PP
D) RR pp × rr Pp
E) Rr pp × Rr Pp

Question 55

In chickens, comb shape is determined by genes at two loci (R, r and P, p). A walnut comb is produced when at least one dominant gene R is present at one locus and at least one dominant gene P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant gene is present at the first locus and two recessive genes are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive genes are present at the first locus and at least one dominant gene is present at the second (genotype rr P_). If two recessive genes are present at the first and the second locus (rr pp), a single comb is produced.

- Give genotypes for comb shape of the parents in the following cross: Rose crossed with single produces 31 rose offspring.

A) RR PP × rr pp
B) RR pp × rr pp
C) Rr PP × rr pp
D) Rr Pp × rr pp
E) Rr pp × rr pp

Question 56

In a certain species of plant, flowers occur in three colors: blue, pink, and white. A pure-breeding pink plant is mated with a pure-breeding white plant. All of the F₁ are blue. When the blue F₁ plants are selfed, the F₂ plants occur in the ratio 9 blue : 3 pink : 4 white.


-What is the name for this type of interaction?

A) recessive epistasis
B) dominant epistasis
C) duplicate recessive epistasis
D) duplicate dominant epistasis
E) dominant and recessive epistasis

Question 57

The very rare Bombay blood phenotype in humans (first discovered in Bombay, India) results in blood type O because of the lack of both the A and B antigens in individuals who are of hh genotype. This genotype results in blood type O regardless of the genotype at the unlinked I locus. If two parents are both of I^A I^B Hh genotype (type AB blood), what is the probability that their first child will also have type blood B?

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

Question 58

In chickens, comb shape is determined by genes at two loci (R, r and P, p). A walnut comb is produced when at least one dominant gene R is present at one locus and at least one dominant gene P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant gene is present at the first locus and two recessive genes are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive genes are present at the first locus and at least one dominant gene is present at the second (genotype rr P_). If two recessive genes are present at the first and the second locus (rr pp), a single comb is produced.

- Give genotypes for comb shape of the parents in the following cross: Walnut crossed with single produces 1 walnut, 1 rose, 1 pea, and 1 single offspring.

A) RR PP × rr pp
B) RR Pp × rr pp
C) Rr PP × rr pp
D) Rr Pp × rr pp
E) Rr pp × rr pp

Question 59

In a certain species of plant, flowers occur in three colors: blue, pink, and white. A pure-breeding pink plant is mated with a pure-breeding white plant. All of the F₁ are blue. When the blue F₁ plants are selfed, the F₂ plants occur in the ratio 9 blue : 3 pink : 4 white. The genotype that produces white is ww. The presence of one W allele allows pink or blue color to occur. The alleles at the hypostatic locus are B (blue) and b (pink).

-What is the genotype of the pink parent?

A) bb WW
B) bb Ww
C) Bb Ww
D) Bb ww
E) BB ww

Question 60

In a certain species of plant, flowers occur in three colors: blue, pink, and white. A pure-breeding pink plant is mated with a pure-breeding white plant. All of the F₁ are blue. When the blue F₁ plants are selfed, the F₂ plants occur in the ratio 9 blue : 3 pink : 4 white.

-How many gene pairs control the flower color phenotype?

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

Question 61

In domestic chickens, some males display a plumage pattern called cock feathering. Other males and all females display a pattern called hen feathering. Cock feathering is an autosomal recessive trait that is exhibited in males only.

-What type of inheritance is exhibited by this trait?

A) sex-linked
B) sex-limited
C) sex-influenced
D) autosomal recessive
E) autosomal dominant

Question 62

A 24-year-old woman with myotonic dystrophy, a genetic disorder caused by a dominant mutant allele, has significant muscle weakness and wasting. She has a 1-year-old son with very poor muscle tone, severe weakness, and significant developmental delay. Her affected 55-year-old father has minor cataracts but no muscle weakness. Which of the following terms BEST describes this situation?

A) codominance
B) complementation
C) multiple alleles
D) compound heterozygote
E) anticipation

Question 63

What phenomenon describes a genetic trait that is expressed more strongly or earlier in development with each generation?

A) epigenetics
B) maternally determined progeny phenotypes
C) epistasis
D) anticipation
E) genomic imprinting

Question 64

Huntington's disease tends to strike earlier and lead to a more rapid progression of symptoms as it moves from generation to generation. Also, it tends to strike earlier and progress more rapidly when it is passed from the father to his children rather than from the mother. Which genetic phenomenon (or phenomena) is/are likely operating here? (Select all that apply.)

A) incomplete penetrance
B) sex-limited inheritance
C) genetic anticipation
D) parental imprinting
E) epistasis

Question 65

The bicoid mutation (bcd^-) in fruit flies is inherited as a maternal effect recessive allele. What is the expected ratio of phenotypes in the offspring of a cross between a bcd⁺/bcd^- female and a bcd⁺/bcd^- male?

A) 1 normal : 1 mutant
B) 3 normal : 1 mutant
C) 3 mutant : 1 normal
D) all normal
E) all mutant

Question 66

In domestic chickens, some males display a plumage pattern called cock feathering. Other males and all females display a pattern called hen feathering. Cock feathering is an autosomal recessive trait that is exhibited in males only.

- Two heterozygous birds are mated. What fraction of the female offspring is expected to exhibit cock feathering?

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

Question 67

In domestic chickens, some males display a plumage pattern called cock feathering. Other males and all females display a pattern called hen feathering. Cock feathering is an autosomal recessive trait that is exhibited in males only.

-Two birds heterozygous for cock feathering are mated. What are the phenotypes of the parents?

A) male with cock feathering, female with hen feathering
B) male with hen feathering, female with cock feathering
C) male with cock feathering, female with cock feathering
D) male with hen feathering, female with hen feathering
E) cannot be determined from the information given

Question 68

Which of the following is a characteristic exhibited by cytoplasmically inherited traits?

A) present in both males and females
B) usually inherited from one parent, typically the maternal parent
C) reciprocal crosses that give different results
D) extensive phenotypic variation exhibited, even within a single family
E) All of the answers are correct.

Question 69

A deletion of a small region on the long arm of chromosome 15 causes a developmental disorder in children called Prader-Willi syndrome when the deletion is inherited from the father. However, the deletion of this same region of chromosome 15 can also be inherited from the mother, but this inheritance results in a completely different set of symptoms, called Angelman syndrome. What type of genetic phenomenon does this represent?

A) sex-influenced
B) genomic imprinting
C) cytoplasmic inheritance
D) maternal effect
E) paternal effect

Question 70

Male-limited precocious puberty results from a rare autosomal allele (P) that is dominant over the allele for normal puberty (p) and is expressed only in males. A male and female that both went through normal puberty have two sons. The first son undergoes precocious puberty but the second undergoes normal puberty.

-What is the genotype of the father?

A) PP
B) Pp
C) pp
D) PP or Pp
E) Pp or pp

Question 71

In domestic chickens, some males display a plumage pattern called cock feathering. Other males and all females display a pattern called hen feathering. Cock feathering is an autosomal recessive trait that is exhibited in males only.

-Two heterozygous birds are mated. What fraction of the male offspring is expected to exhibit cock feathering?

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

Question 72

The cross of CcDd × CcDd results in a 12:3:1 phenotypic ratio. What is the expected phenotypic ratio when a CcDd × ccdd testcross is made involving the same two genes? (They are assorting independently.)

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

Question 73

Male-limited precocious puberty results from a rare autosomal allele (P) that is dominant over the allele for normal puberty (p) and is expressed only in males. A male and female that both went through normal puberty have two sons. The first son undergoes precocious puberty but the second undergoes normal puberty.

-What is the genotype of the mother?

A) PP
B) Pp
C) pp
D) PP or Pp
E) Pp or pp

Question 74

Discuss the difference between "cytoplasmic inheritance" and "genetic maternal effect."

Question 75

In domestic chickens, some males display a plumage pattern called cock feathering. Other males and all females display a pattern called hen feathering. Cock feathering is an autosomal recessive trait that is exhibited in males only.

- Two heterozygous birds are mated. What fraction of the total offspring is expected to exhibit cock feathering?

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

Question 76

Assume that a human gene is imprinted. Normal individuals have one active copy of the gene, the copy inherited from their fathers. The copy inherited from their mothers is normally inactive.
In one large family a mutation in this gene occurs and this mutation results in part of the gene being deleted. The defective gene is never active regardless of the parent from which it is inherited. Individuals who carry the mutation are heterozygous and also have a normal copy of the gene whose activity depends upon which parent it was inherited from. Individuals who have no active copy of the gene have several medical problems but live long enough to have children of their own. This family includes two phenotypically normal parents who have two affected children, a son and a daughter. Which parent, father or mother, did the affected children inherit this mutation from? Why?

Question 77

Which organelle in an animal cell, in addition to the nucleus, contains genes?

A) lysosome
B) ribosome
C) mitochondrion
D) Golgi body
E) vesicle

Question 78

The phenomenon in which a gene's expression is determined by its parental origin is called:

A) sex-influenced.
B) sex-limited.
C) genomic imprinting.
D) maternal effect.
E) paternal effect.

Question 79

The red kernel color in wheat is caused by the presence of at least one dominant allele in each of two independently segregating gene pairs (e.g., R_B_). Wheat plants with rrbb genotypes have white kernels, and plants with genotypes R_bb and rrB_ have yellow kernels. You cross a plant homozygous for red kernels (RR BB) with a plant homozygous for white kernels. What are the relative proportions of the phenotypic classes expected in the F₂ progeny after selfing the F₁ progeny?

A) 9 red; 3 white; 4 yellow
B) 9 red; 6 yellow; 1 white
C) 9 yellow; 4 red; 1 white
D) 9 red; 3 yellow; 4 white
E) 12 red; 3 yellow; 1 white

Question 80

Leber hereditary optic neuropathy (LHON) is a human disease that exhibits cytoplasmic inheritance. It is characterized by rapid loss of vision in both eyes, resulting from the death of cells in the optic nerve. A teenager loses vision in both eyes and is later diagnosed with LHON. How did this individual MOST likely inherit the mutant DNA responsible for this condition?

A) a nuclear gene from the father
B) a nuclear gene from the mother
C) a mitochondrial gene from the father
D) a mitochondrial gene from the mother
E) Any of these answers is possible.