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

Accepted Answer

Dominant suppression occurs when a dominant allele of one gene completely suppresses the phenotypic expression of alleles of another gene.

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

Accepted Answer

Epistasis is a gene interaction where an allele of one gene can modify or prevent expression of alleles of another gene. This can result in certain phenotypes being masked or completely suppressed. Examples of epistasis include recessive epistasis and dominant epistasis. Incomplete dominance, codominance, complete dominance, and incomplete penetrance are not types of gene interactions where one gene modifies or prevents expression of alleles of another gene.

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

Accepted Answer

Incomplete penetrance is the best explanation as it means that not all individuals with the dominant mutant polydactyly allele express the phenotype (extra digits) even though they have the genotype. Therefore, the 25% of individuals with the normal number of digits could carry the mutant allele but not express the phenotype due to incomplete penetrance.

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

Accepted Answer

The fact that the heterozygote exhibits 0 units of enzyme activity points to a dominant negative allele, where the mutant protein product interferes with the function of the wild-type protein. The mutant allele is not null (choice A) as it produces a non-functioning protein, and not hypomorphic (choice B) as it produces no enzyme activity at all. It is not hypermorphic (choice C) as it does not produce more enzyme activity than the wild-type allele. It is also not neomorphic (choice E) as it does not produce a novel enzyme activity.

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

Accepted Answer

The answer of Bateson and Punnett crossed two white-flowered lines...

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

Accepted Answer

In codominance, both alleles are expressed equally in the heterozygous phenotype. This means that the phenotype shows features of both alleles equally, rather than an intermediate trait or only expressing one of the alleles.

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

Accepted Answer

A neomorphic mutation results in a gene product with a novel function that is not normally found in wild-type organisms. Amorphic mutations result in a complete loss of function, hypomorphic mutations result in a partial loss of function, hypermorphic mutations result in a gene product with an increased function, and dominant negative mutations result in a gene product that interferes with the function of the wild-type gene product.

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

Accepted Answer

Lethal alleles can cause one class of expected progeny to be missing, which results in a distortion in segregation ratios. This occurs because homozygotes for the lethal allele die during development, and thus the expected phenotypic ratio is disrupted. Dominant negative alleles, temperature-sensitive alleles, partial dominance, and incomplete penetrance may also affect segregation ratios, but they do not necessarily cause the absence of a specific class of progeny.

Question 9

A mutation resulting in an inactive gene product is classified as __________.
A)amorphic
B)hypomorphic
C)hypermorphic
D)neomorphic
E)dominant negative

Accepted Answer

An amorphic mutation results in a complete loss-of-function of the gene product, resulting in an inactive protein. A hypomorphic mutation results in a reduced function of the gene product, while a hypermorphic mutation results in an increased function of the gene product. A neomorphic mutation results in a new and different function of the gene product. A dominant negative mutation results in the mutant protein interfering with the function of the normal protein.

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

Accepted Answer

In incomplete dominance, the heterozygote expresses a phenotype that is intermediate between the two homozygotes. However, it is not exactly a blend of the two, and often more closely resembles one homozygote than the other. This results in the heterozygote having a phenotype that is different from either homozygote.

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

Accepted Answer

The 2:1 ratio suggests that the allele is lethal when homozygous, as homozygous individuals do not survive, leaving only heterozygous and wild-type individuals.

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

Accepted Answer

A hypomorphic mutation is one that reduces the activity of a gene or protein, but does not completely eliminate its function. This is in contrast to an amorphic mutation, which completely abolishes function, or a neomorphic mutation, which creates a new function for the protein. A hypermorphic mutation increases the activity of a gene or protein, and a dominant negative mutation interferes with the function of the wild-type allele even when only one copy of the mutation is present. Therefore, the most appropriate choice for a mutation that results in an enzyme that is partially active is a hypomorphic mutation.

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

Accepted Answer

Individuals with blood type O have two recessive alleles, which are represented by "i." Therefore, the genotype for individuals with blood type O is "ii."

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

Accepted Answer

The answer of Many oncogenes result from mutations that cause...

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

Accepted Answer

The combination I^AI^B results in codominance, where both A and B antigens are expressed equally, leading to the AB blood type.

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

Accepted Answer

Complete dominance is the mode of inheritance where the phenotype of a heterozygote is indistinguishable from the phenotype of an organism homozygous for the dominant allele. This means that the dominant allele completely masks the recessive allele, resulting in only one phenotype being expressed in the heterozygote.

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.

Accepted Answer

The WT and mutant alleles show incomplete dominance because the heterozygote has an intermediate phenotype (300 units) between the homozygotes (200 and 400 units).

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

Accepted Answer

This type of mutation is classified as dominant negative, which means that the mutated protein interferes with the activity of the non-mutated protein, leading to a loss of overall function in the multimeric protein.

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

Accepted Answer

The answer of The 9:6:1 ratio seen in the dihybrid...

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

Accepted Answer

The mutant allele is hypermorphic because it results in increased enzyme activity compared to the wild-type allele.

Quiz 4: Gene Interaction

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

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

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?

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?

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?

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

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 __________.

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

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

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

What is the genotype for individuals with blood type O?

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 __________.

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

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

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 __________.

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

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?

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?