Deck 4: Inheritance Patterns of Single Genes and Gene Interaction

Question 1

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

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

Answer 1

E

Question 2

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

Answer 2

A

Question 3

A man with blood type A (whose mother was blood type O) has children with a woman that has blood type AB. The man and the woman are also heterozygous for the H antigen. What is the probability that they will have a child with blood type A?

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

Answer 3

E

Question 4

In certain goat breeds, appearance of a chin beard is a sex- influenced trait. Recall that bearding is inherited as an autosomal trait determined by two alleles, B1 and B2, and females must be homozygous for the bearded allele, B2, to have a beard. What genotypes must a bearded billy goat (male) and a beardless female goat have if they have a bearded female offspring?

A) The bearded billy goat must be heterozygous for the bearded allele, while the beardless female must be homozygous for the bearded allele.
B) The bearded billy goat could be heterozygous or homozygous for the bearded allele, while the beardless female must be homozygous for the bearded allele.
C) Both the bearded billy goat and beardless female must be heterozygous for the bearded allele.
D) The bearded billy goat could be heterozygous or homozygous for the bearded allele, while the beardless female must be heterozygous for the bearded allele.
E) Both the bearded billy goat and beardless female must be homozygous for the bearded allele.

Question 5

Which of the following is correct regarding individuals who are blood type AB?

A) Their blood cells clump when they receive blood from an individual with the genotype IAi.
B) They express B- transferase that adds N- acetylgalactosamine to the H antigen.
C) They do not carry the A or B antigen.
D) They are the universal recipients.
E) They carry both the anti- A and anti- B antibodies.

Question 6

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) null/ amorphic
B) hypomorphic
C) hypermorphic
D) neomorphic
E) dominant negative

Question 7

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) null/ amorphic
B) hypomorphic
C) hypermorphic
D) neomorphic
E) dominant negative

Question 8

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 9

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) neomorphic
B) hypermorphic
C) hypomorphic
D) null/ amorphic
E) dominant negative

Question 10

Which phenomenon explains differences in the inheritance patterns of the appearance of a chin beard between males and females of certain species of goats, even when their genotypes are the same?

A) sex- limited trait
B) lethal allele
C) sex- influenced trait
D) incomplete penetrance
E) variable expressivity

Question 11

The parental cross between a rabbit with the Himalayan phenotype (genotype chch) and an albino rabbit (genotype cc) results in F1 rabbits that all have the Himalayan phenotype (genotype chc). If the resulting F1 rabbits are crossed, what proportion of the F2 offspring will have the Himalayan phenotype and what causes the hypomorphic ch allele to be unstable and result in the distinctive fur pattern?

A) 3/4; complementation
B) 1/2; complementation
C) 3/4; temperature
D) 1/4; temperature
E) 1/2; temperature

Question 12

Many oncogenes result from mutations that cause excessive expression of a protein 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) hypomorphic
B) dominant negative
C) amorphic
D) hypermorphic
E) neomorphic

Question 13

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

Question 14

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

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

Question 15

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

Question 16

Brachydactyly type D is human autosomal dominant condition in which the thumbs are abnormally short and broad. In most cases, both thumbs are affected, but occasionally just one thumb is involved. The pedigree above shows a family in which brachydactlyly type D is segregating. Filled circles and squares represent females and males who have involvement of both thumbs. Half- filled in symbols represent family members with just one thumb affected? There is evidence of variable expressivity and incomplete penetrance in this family. Which individu most likely nonpenetrant for the trait?

A) II- 4
B) IV- 1
C) IV- 5
D) III- 5
E) III- 11

Question 17

Brachydactyly type D is human autosomal dominant condition in which the thumbs are abnormally short and broad. In most cases, both thumbs are affected, but occasionally just one thumb is involved. The pedigree above shows a family in which brachydactlyly type D is segregating. Filled circles and squares represent females and males who have involvement of both thumbs. Half- filled in symbols represent family members with just one thumb affected?
There is evidence of variable expressivity and incomplete penetrance in this family. Which individu most likely nonpenetrant for the trait?

A) III- 10
B) III- 11
C) IV- 1
D) II- 4
E) IV- 5

Question 18

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) hypermorphic
B) hypomorphic
C) neomorphic
D) null/ amorphic
E) dominant negative

Question 19

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 20

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

Question 21

Which step is catalyzed by the enzyme responsible for the Met 2 mutant? $\begin{array} { l } \text { Growth Medium }\\\hline \begin{array} { l } \text { Mutant }\\ \text {strain }\\\end{array}&\begin{array} { l } \text { Minimal}\\ \text { medium}\\\end{array}&\begin{array} { l } \text { Minimal+}\\ \text {cysteine }\\\end{array}&\begin{array} { l } \text { Minimal+}\\ \text {cystathionine }\\\end{array}&\begin{array} { l } \text {Minimal+ }\\ \text {homocysteine }\\\end{array}&\begin{array} { l } \text { Minimal+}\\ \text { methionine}\\\end{array}&\begin{array} { l } \text { Compound}\\ \text { accumulating}\\ \text { in mutant}\\\end{array}\\\hline\begin{array} { l } \text { Control}\\ \text {prototroph }\\\end{array}&+&+&+&+&+& \text {None }\\\text { Met } 1&-&-&-&-&+&\text { Homocysteine }\\\text { Met } 2&-&-&-&+&+&\text { Cystathionine }\\\text { Met } 3&-&-&+&+&+&\text { Cysteine }\\\text { Met } 4&-&+&+&+&+&\text { Homoserine }\\\end{array}$

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

Question 22

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

Question 23

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 definitively conclude?

A) The haploid strains have identical mutations in the same genes.
B) The haploid strains must belong to the complementation group encoding the first enzyme in the biosynthetic pathway.
C) The haploid strains have identical mutations in different genes.
D) The haploid strains have mutations in the same gene.
E) The haploid strains have mutations in different genes.

Question 24

Wild- type bacteria can grow on minimal medium. Four mutants that cannot grow on minimal med but can grow on minimal medium supplemented with the nutrient "H" are isolated. It is suspected t metabolites T, P, and A are in the biochemical pathway for synthesis of H, so each mutant is tested f ability to grow on minimal medium supplemented with these metabolites: A. Mutant 1: can grow on minimal medium supplemented with T, but not P or A
B) Mutant 2: is unable to grow on minimal medium supplemented with T, P, or A
C) Mutant 3: is able to grow on minimal medium supplemented with A or T, but not P
D) Mutant 4: can grow on minimal medium supplemented with T, P, or A.
Which of the following is NOT consistent with this information?

A) Mutant 1 will cause a build up of metabolite A
B) Mutant 4 blocks a step before all the metabolites
C) Mutant 3 blocks the conversion of metabolite P -metabolite A
D) Mutant 3 will cause a build up of metabolite T
E) Mutant 2 blocks a step right before metabolite H

Question 25

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?
$\begin{array} { l } \text { Growth Medium }\\\hline \begin{array} { l } \text { Mutant }\\ \text {strain }\\\end{array}&\begin{array} { l } \text { Minimal}\\ \text { medium}\\\end{array}&\begin{array} { l } \text { Minimal+}\\ \text {cysteine }\\\end{array}&\begin{array} { l } \text { Minimal+}\\ \text {cystathionine }\\\end{array}&\begin{array} { l } \text {Minimal+ }\\ \text {homocysteine }\\\end{array}&\begin{array} { l } \text { Minimal+}\\ \text { methionine}\\\end{array}&\begin{array} { l } \text { Compound}\\ \text { accumulating}\\ \text { in mutant}\\\end{array}\\\hline\begin{array} { l } \text { Control}\\ \text {prototroph }\\\end{array}&+&+&+&+&+& \text {None }\\\text { Met } 1&-&-&-&-&+&\text { Homocysteine }\\\text { Met } 2&-&-&-&+&+&\text { Cystathionine }\\\text { Met } 3&-&-&+&+&+&\text { Cysteine }\\\text { Met } 4&-&+&+&+&+&\text { Homoserine }\\\end{array}$

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

Question 26

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

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

Question 27

In sheep, coat color is influenced by two genes. Gene A influences pigment production, while gene B produces black or brown pigment. If two heterozygous white sheep resulted in 12 white sheep, 3 black sheep, and 1 brown sheep, which genotype(s) of the white sheep explain this data?

A) The white sheep could be A_B_ or aabb.
B) The white sheep must all be A_B_.
C) The white sheep could be A_B_ or A_bb.
D) The white sheep must all be aabb.
E) The white sheep could be A_B_ or aaB_.

Question 28

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?

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

Question 29

Bateson and Punnett crossed two white- flowered lines and saw all purple flowers in the F1 generat 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) 16 purple to 0 white
B) 7 purple to 9 white
C) 0 purple to 16 white
D) 9 purple to 7 white
E) 8 purple to 8 white

Question 30

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

Question 31

Wild- type bacteria can grow on minimal medium. Four mutants that cannot grow on minimal med but can grow on minimal medium supplemented with the nutrient "H" are isolated. It is suspected t metabolites T, P, and A are in the biochemical pathway for synthesis of H, so each mutant is tested f ability to grow on minimal medium supplemented with these metabolites: A. Mutant 1: can grow on minimal medium supplemented with T, but not P or A
B) Mutant 2: is unable to grow on minimal medium supplemented with T, P, or A
C) Mutant 3: is able to grow on minimal medium supplemented with A or T, but not P
D) Mutant 4: can grow on minimal medium supplemented with T, P, or A.
Which of the following is NOT consistent with this information?

A) Mutant 3 blocks the conversion of metabolite P -metabolite A
B) Mutant 4 blocks a step before all the metabolites
C) Mutant 1 will cause a build up of metabolite A
D) Mutant 1 blocks the conversion of metabolite T -metabolite H
E) Mutant 2 blocks a step right before metabolite H

Question 32

A certain species of morning glories produces flowers that are blue, red, or purple. Two pure- breeding purple lines are crossed and produce F1 progeny that all make blue flowers. The F1 allowed to self and produce 320 F2 progeny with the following distribution: 185 blue, 115 purple, an red.
Which the following is NOT consistent with this information?

A) Blue- flowering plants are either A_bb or aaB_.
B) The pure- breeding parental parents are homozygous recessive for mutations in two different genes.
C) Dominant gene interaction appears to result in a 9:6:1 ratio.
D) Analysis of the F1 and F2 progeny phenotypes suggests epistasis.
E) Red- flowering plants are homozygous recessive for both genes.

Question 33

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

Question 34

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 mutations are codominant to the normal allele.
B) The parents have the same mutated protein involved in inner ear development.
C) The parents have mutations in different genes.
D) The mutations are incompletely dominant to the normal allele.
E) The parents have mutations in the same gene.

Question 35

You are looking at the color of feathers in ducks and find that yellow ducks (Y) are dominant to green ducks (y). However, a second gene, H, controls whether the color will be expressed in the feathers. If the duck is hh, the duck will always be white, because the pigment does not go into feathers. What ratio of phenotypes would you expect following a dihybrid cross?

A) 15:1
B) 12:3:1
C) 9:3:4
D) 9:6:1
E) 13:3

Question 36

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 37

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

Question 38

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 epistasis
B) dominant suppression
C) complementary gene interaction
D) dominant epistasis
E) dominant gene interaction

Question 39

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 40

Complementation tests of distinct recessive mutants, 1 through 8, produce the data in the matrix below. A plus (+) indicates complementation, meaning the phenotype of the combined alleles is wild type, and a minus (- ) indicates a failure to complement meaning that a mutant phenotype results. Assume that the missing mutant combinations would yield data consistent with the entries that are shown. How many complementation groups are formed by these eight mutants?

A) 4
B) 5
C) 6
D) 2
E) 3

Question 41

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 42

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

Question 43

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

Question 44

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 45

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

Question 46

People with the dominant mutant polydactyly allele can have extra digits on one or both of their hands. What is the genetic explanation for this observation?

Question 47

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

Question 48

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

Question 49

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 50

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 51

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 52

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 53

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 54

Amorphic, hypomorphic, and dominant negative mutations are mutations, which decrease or eliminate gene activity.

Question 55

Hypermorphic and neomorphic mutations are _ mutations, which cause overexpression or result in new functions.

Question 56

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 57

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 58

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?

Question 59

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

Question 60

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 61

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.