Deck 4: Gene Interaction

Question 1

If a dominant allele of one gene completely suppresses the phenotypic expression of alleles of another gene, this is an example of __________.

A)recessive interaction
B)dominant interaction
C)recessive epistasis
D)dominant epistasis
E)dominant suppression

Answer 1

E

Question 2

Gene interactions in which an allele of one gene modifies or prevents expression of alleles of another gene is known as __________.

A)complete dominance
B)incomplete dominance
C)codominance
D)epistasis
E)incomplete penetrance

Answer 2

D

Question 3

Most people with the dominant mutant polydactyly allele have extra digits, but at least 25% have the normal number of digits. What is the genetic explanation for this observation?

A)dominant negative allele
B)temperature-sensitive allele
C)lethal allele
D)partial dominance
E)incomplete penetrance

Answer 3

E

Question 4

The amount of enzyme activity in a cell that is homozygous for a mutant allele is 0 units. The amount of enzyme activity in a cell homozygous for the WT allele is 200 units. The amount of enzyme activity in a heterozygote is 0 units. What type of allele is the mutant allele?

A)null
B)hypomorphic
C)hypermorphic
D)dominant negative
E)neomorphic

Question 5

Bateson and Punnett crossed two white-flowered lines and saw all purple flowers in the F₁ generation. They concluded this was an example of complementary gene interactions because a cross of the F₁ plants yielded what ratio in the F₂ generation?

A)8 purple to 8 white
B)16 purple to 0 white
C)0 white to 16 purple
D)7 purple to 9 white
E)9 purple to 7 white

Question 6

Which mode of inheritance results in both alleles being detected equally in the heterozygous phenotype?

A)complete dominance
B)incomplete dominance
C)codominance
D)epistasis
E)incomplete penetrance

Question 7

A mutation results in a gene product with a novel function that is not normally found in wild-type organisms. This type of mutation is known as __________.

A)amorphic
B)hypomorphic
C)hypermorphic
D)neomorphic
E)dominant negative

Question 8

What type of allele is often detected as a distortion in segregation ratios, where one class of expected progeny is missing?

A)dominant negative allele
B)temperature-sensitive allele
C)lethal allele
D)partial dominance
E)incomplete penetrance

Question 9

A mutation resulting in an inactive gene product is classified as __________.

A)amorphic
B)hypomorphic
C)hypermorphic
D)neomorphic
E)dominant negative

Question 10

Which mode of inheritance produces heterozygotes with phenotypes that differ from either homozygote but typically more closely resembles one homozygous phenotype than the other?

A)complete dominance
B)incomplete dominance
C)codominance
D)epistasis
E)incomplete penetrance

Question 11

You discover a new allele of a gene important for tail formation in mice. WT mice have long tails, but mice heterozygous for the allele have short tails. When you cross two heterozygous mice together, you obtain a 2:1 ratio of short-tailed mice to long-tailed mice. None of the short-tailed progeny are homozygous. What type of allele results in short tails?

A)dominant negative allele
B)temperature-sensitive allele
C)lethal allele
D)partially dominant allele
E)incompletely penetrant allele

Question 12

A mutation results in an enzyme that is partially active compared to the wild-type allele. This type of "leaky" mutation is classified as __________.

A)amorphic
B)hypomorphic
C)hypermorphic
D)neomorphic
E)dominant negative

Question 13

What is the genotype for individuals with blood type O?

A)I^Ai
B)I^AI^B
C)I^Bi
D)ii
E)either I^Ai or I^Bi

Question 14

Many oncogenes result from mutations that cause a protein to be expressed in cells where it is normally not expressed or is expressed at inappropriate times during development. This type of mutation can be described as __________.

A)amorphic
B)hypomorphic
C)hypermorphic
D)neomorphic
E)dominant negative

Question 15

Most combinations of different ABO alleles result in complete dominance of one allele. Which combination results in codominance?

A)I^Ai
B)I^AI^B
C)I^Bi
D)ii
E)either I^Ai or I^Bi

Question 16

Which mode of inheritance results in the phenotype of a heterozygote being indistinguishable from that of an organism homozygous for the dominant allele?

A)complete dominance
B)incomplete dominance
C)codominance
D)epistasis
E)incomplete penetrance

Question 17

The amount of enzyme activity in a cell that is homozygous for a mutant allele is 400 units. The amount of enzyme activity in a cell homozygous for the WT allele is 200 units. The amount of enzyme activity in a heterozygote is 300 units. What is the dominance relationship between the WT and mutant allele for the phenotype of amount of enzyme per cell?

A)The WT allele is dominant.
B)The mutant allele is dominant.
C)The WT and mutant alleles are codominant.
D)The WT and mutant alleles show incomplete dominance.
E)It is impossible to determine from the information given.

Question 18

Two proteins interact to form a multimeric complex. When one of the proteins is mutated, there is a substantial loss of functional activity in the multimeric protein. This type of mutation is classified as __________.

A)amorphic
B)hypomorphic
C)hypermorphic
D)neomorphic
E)dominant negative

Question 19

The 9:6:1 ratio seen in the dihybrid cross of summer squash indicates what genetic relationship between the two genes controlling fruit shape?

A)recessive interaction
B)dominant interaction
C)recessive epistasis
D)dominant epistasis
E)dominant suppression

Question 20

The amount of enzyme activity in a cell that is homozygous for a mutant allele is 400 units. The amount of enzyme activity in a cell homozygous for the WT allele is 200 units. The amount of enzyme activity in a heterozygote is 300 units. What type of allele is the mutant allele?

A)null
B)hypomorphic
C)hypermorphic
D)dominant negative
E)neomorphic

Question 21

Which antigen, expressed on the surface of all red blood cells, is modified by A- or B-transferases?

Question 22

A metabolic reaction requires 10 units of enzymatic activity to proceed. If a dominant allele D can generate 8 units of enzyme and a recessive allele d can generate 2 units of enzyme, what can be said of the dominant wild-type allele?

Question 23

A metabolic reaction requires 40 units of enzymatic activity to proceed. If a dominant allele D can generate 40 units of enzyme and a mutant allele d" generates 20 units of enzyme, what can be said of the dominant wild-type allele?

Question 24

What are the two categories of gain-of-function mutations?

Question 25

In yeast, there are three gene products required to synthesize the amino acid lysine. You cross two haploid lysine auxotrophs to form a diploid. The diploid fails to grow on plates lacking lysine. Which of the following can you conclude?

A)The haploid strains have mutations in the same gene.
B)The haploid strains have mutations in different genes.
C)The haploid strains form a complementation group.
D)The haploid strains do not complement each other.
E)Both (A)and (D)are true.

Question 26

You cross a pure-breeding white flower with a pure-breeding red flower, and the offspring are white with red spots. This is an example of what type of inheritance?

Question 27

The four different human blood types are caused by how many different alleles? What are the alleles?

Question 28

You cross a pure-breeding white flower with a pure-breeding red flower, and the offspring are all pink. This is an example of what type of inheritance?

Question 29

Which step is catalyzed by the enzyme responsible for the Met 3 mutant?

A)homoserine → cysteine
B)cysteine → cystathionine
C)cystathionine → homocysteine
D)homocysteine → methionine
E)methionine → homoserine

Question 30

Individuals with blood type AB have which blood antibody(ies)?

Question 31

An individual who is a "universal acceptor," meaning he or she will not have an adverse reaction to a transfusion with any type of blood, has which blood type?

Question 32

In the biosynthetic pathway for conversion from homoserine to methionine, you identify a Neurospora crassa double mutant Met1/Met2. This mutant will grow only if which supplement(s)are added to the minimal media?

A)homoserine only
B)cysteine only
C)homocysteine only
D)cystathionine and homocysteine
E)methionine only

Question 33

Two pure-breeding mutant plants produce white flowers. When they are crossed, all of the progeny have wild-type purple flowers. What does this genetic complementation tell you?

A)The genes are part of distinct biosynthetic pathways.
B)The two lines exhibit different mutations in the same gene.
C)More than one gene is involved in determining the phenotype.
D)The allele is pleiotropic.
E)The allele exhibits incomplete dominance.

Question 34

Alleles of the Sbe1 gene, which controls pea shape, can be detected by DNA analysis. In heterozygous plants, two distinct bands of DNA are visible. What is the relationship between the alleles of the heterozygote at the molecular level?

Question 35

Individuals with blood type A have which blood antigen(s)?

Question 36

Independent assortment predicts a 9:3:3:1 ratio with four different phenotypes in the F₂ progeny. If the alleles are epistatic, what would you predict?

A)more than four phenotypes
B)fewer than four phenotypes
C)heterozygotes with a novel phenotype between the dominant and recessive homozygotes
D)1/3 of the progeny with the dominant phenotypes and 2/3 recessive
E)no change in the 9:3:3:1 ratio

Question 37

The allele responsible for the Siamese coat-color pattern produces an unstable tyrosinase enzyme. This type of gene product is an example of what type of allele?

Question 38

Are loss-of-function mutations more likely to be dominant or recessive?

Question 39

Deafness is caused by recessive mutations in any one of at least five genes. Two deaf individuals have nine children, all of whom have normal hearing. Which of the following can you conclude?

A)The parents have mutations in the same gene.
B)The parents have mutations in different genes.
C)An epistatic interaction has occurred.
D)The mutations are codominant to the normal allele.
E)The mutations are incompletely dominant to the normal allele.

Question 40

What are the three categories of loss-of-function mutations?

Question 41

In familial hypercholesterolemia, individuals who are homozygous for the mutation lack LDL cholesterol receptors in the liver, causing high levels of serum cholesterol. This is a defect in which type of gene pathway: a biosynthetic, signal transduction, or developmental pathway?

Question 42

King George III of England and other members of the royal family were afflicted with a series of strange, seemingly unrelated symptoms including abdominal pain, rapid pulse, convulsions, and insanity. It has been determined that he likely suffered from porphyria, caused by a mutation in a single allele. What is the genetic term describing the alteration of multiple, distinct traits of an organism by a mutation in a single gene?

Question 43

To better understand which genes are involved in developmental pathways, geneticists use experimental analyses of mutant phenotypes. What is this analytic approach called?

Question 44

In Labrador retrievers, coat color is controlled by gene interaction in which homozygosity for a recessive allele can mask the phenotypic expression of a second gene. This genetic interaction is known as ________ and has a characteristic ________ ratio.

Question 45

Mendel studied tall and short pure-breeding lines of pea plants. Inherited genetic variation would dictate that one line would produce tall plants and the other short plants, but the genes and phenotypes are influenced by what external factor?

Question 46

Numerous genes contribute to the wild-type red eye color in Drosophila. Two genes, brown and vermilion, produce eye pigments. What does the white gene do?

Question 47

IA and IB alleles exhibit ________ (complete or incomplete)dominance over the i allele.

Question 48

If an organism with a particular genotype fails to produce the corresponding phenotype, the organism is said to be ________ for the trait.

Question 49

________ mutations decrease or eliminate gene activity.

Question 50

Explain how the ch (Himalayan)allele and tyrosinase control the Siamese coat-color pattern. What is the underlying reason that certain parts of a Siamese cat (e.g., tail and ears)are darker than the cat's trunk?

Question 51

Phenylketonuria (PKU)is caused by the absence of the enzyme phenylalanine hydroxylase, which catalyzes the first step of the pathway that breaks down the amino acid phenylalanine, a common component of dietary protein. Explain how environmental intervention is commonly practiced to prevent the development of this human autosomal recessive condition.

Question 52

Proper cross-matching of blood type is essential for safe blood transfusion. What is the general rule for safe blood transfusion, and what are the consequences if a patient receives the incorrect blood type by accident? If a patient's blood type is unknown, what is the safest course of action?

Question 53

________ mutations cause overexpression or result in new functions.

Question 54

You have crossed two Mexican hairless dogs, and the offspring are 1/3 hairy and 2/3 hairless. Given this phenotypic ratio, draw the Punnett square for this cross. What are the genotypes of the P₁ and F₁ dogs in this cross? List the predicted genotype as well as the phenotype for each of the offspring. Which genotypes are hairless, and which are hairy? Can you design a genetic cross that would yield a true-breeding hairless line (where all offspring are hairless)?

Question 55

Describe the difference between incomplete penetrance and variable expressivity. It is often difficult to pinpoint the cause of incomplete penetrance or variable expressivity. What possible interactions may be responsible?

Question 56

Which type of pathway is responsible for melanin production: a biosynthetic pathway, signal transduction pathway, or developmental pathway?