Chapter 04: Extensions of Mendelian Inheritance

True or False: Male-pattern baldness is solely inherited in an autosomal dominant manner in humans.

A) True

B) False

B) False

True or False: In an epistatic interaction, the genes must be located on the same chromosome.

A) True

B) False

B) False

True or False: Typically, a recessive allele increases the expression of a functional protein.

A) True

B) False

B) False

True or False: Human blood groups are determined by antigens on the surface of red blood cells.

A) True

B) False

A) True

True or False: Incomplete penetrance indicates that individuals who possess a dominant trait always express the trait.

A) True

B) False

B) False

True or False: Variable expressivity means that the phenotype of a trait can vary between individuals.

A) True

B) False

A) True

True or False: Paralogs are often functionally redundant and can compensate for the loss of either of the paralogs in a set.

A) True

B) False

A) True

True or False: In codominance, both alleles make functional gene products which are expressed simultaneously.

A) True

B) False

A) True

True or False: In sex-influenced traits, both sexes can express the trait, but in sex-limited inheritance a particular sex can only have one phenotype.

A) True

B) False

A) True

True or False: MITF reduced expression confers white spotting due to an increased number of melanocytes.

A) True

B) False

B) False

Genes not required for survival, but likely to be beneficial to the organism, are called:

A) Essential genes

B) Nonessential genes

C) Lethal genes

D) Conditional genes

B) Nonessential genes

Temperature-sensitive alleles that kill an organism only in a particular temperature range are examples of:

A) Wild-type alleles

B) Conditional lethal alleles

C) Pleiotropic alleles

D) Neutral alleles

B) Conditional lethal alleles

The allele that causes Huntington disease in humans is an example of a(n) that exerts its effects later in life.

A) Lethal allele

B) Recessive neutral allele

C) Conditional allele

D) Silent allele

A) Lethal allele

A heterozygote with a phenotype intermediate between homozygous dominant and homozygous recessive is an example of:

A) Complete dominance

B) Codominance

C) Incomplete dominance

D) Overdominance

C) Incomplete dominance

In four-o'clock plants, crossing a pink-flowered plant with a white-flowered plant produces offspring with what phenotypic ratio?

A) All pink

B) ½ pink, ½ white

C) ¾ pink, ¼ white

D) All white

B) ½ pink, ½ white

Coat characteristics of arctic foxes and Siamese cats where proteins function differently in extremities are examples of:

A) Temperature-sensitive allele

B) Codominant allele

C) Overdominant allele

D) Lethal allele

A) Temperature-sensitive allele

In rabbits with a multiple allele coat color hierarchy, if two chinchilla rabbits mate, what coat color is not possible?

A) Chinchilla

B) Himalayan

C) Full coat color

D) Albino

C) Full coat color

Having an AB blood type in humans is an example of:

A) Incomplete dominance

B) Codominance

C) Complete dominance

D) Overdominance

B) Codominance

If an individual with type A blood and an individual with type B blood mate, what blood type is not possible?

A) Type O

B) Type AB

C) Type A

D) All blood types are possible

D) All blood types are possible

At the molecular level, type A and type B blood differ in antigens, sugars, and generated antibodies. Correct?

A) Only in antigens

B) Only in sugars

C) Only in antibodies

D) All of the answers are correct

D) All of the answers are correct

When a heterozygous individual has a selective advantage over homozygous individuals, it is called:

A) Underdominance

B) Overdominance

C) Complete dominance

D) Incomplete dominance

B) Overdominance

Being heterozygous for the sickle cell allele is an example of:

A) Heterozygous advantage

B) Homozygous advantage

C) Lethal trait

D) Codominance

A) Heterozygous advantage

Molecular explanations for heterozygous advantage and overdominance include:

A) Disease resistance

B) Homodimer formation

C) Functional variation

D) All of the answers are possibilities

D) All of the answers are possibilities

An individual carrying the dominant polydactyly allele but remaining phenotypically normal demonstrates:

A) Complete penetrance

B) Incomplete penetrance

C) Variable expressivity

D) Codominance

B) Incomplete penetrance

What does a trait being 70% penetrant mean?

A) 70% of the population has the allele.

B) Only 70% of individuals who carry the allele(s) for a trait express it.

C) The trait is expressed 70% of the time in every individual.

D) 70% of offspring will be homozygous.

B) Only 70% of individuals who carry the allele(s) for a trait express it.

Phenylketonuria in humans is a classic example of:

A) A purely genetic trait

B) An environmentally-influenced trait

C) A sex-limited trait

D) A lethal mutation

B) An environmentally-influenced trait

An autosomal allele that is dominant in one sex and recessive in another exhibits:

A) Sex-limited inheritance

B) Sex-influenced inheritance

C) X-linked recessive inheritance

D) Codominance

B) Sex-influenced inheritance

If a woman heterozygous for X-linked pattern baldness marries a nonbald man, what is the expected offspring phenotype?

A) All offspring bald

B) All females nonbald, ½ of males bald

C) ½ females bald, all males nonbald

D) All offspring nonbald

B) All females nonbald, ½ of males bald

A paralog ____.

A) Is always lethal when mutated

B) Can explain the lack of phenotype for a gene knockout

C) Always results in complete dominance

D) Prevents crossing over

B) Can explain the lack of phenotype for a gene knockout

The interaction of two genes to produce a phenotype was first described by:

A) Mendel and Darwin

B) Bateson and Punnett

C) Watson and Crick

D) Morgan and Sturtevant

B) Bateson and Punnett

Epistasis is defined as:

A) When two genes blend their phenotypes

B) When one gene can mask the expression of a second gene

C) When alleles show incomplete dominance

D) When a gene has multiple effects

B) When one gene can mask the expression of a second gene

Observing a 9:7 phenotypic ratio in a dihybrid cross of heterozygous individuals most likely indicates:

A) Simple Mendelian inheritance

B) Epistatic interaction of the two genes

C) Incomplete dominance

D) Codominance

B) Epistatic interaction of the two genes

Which statement about epistatic interactions is incorrect?

A) They involve two or more genes.

B) They can result in various phenotypic ratios.

C) They always result in a 9:7 ratio of a dihybrid cross.

D) One gene masks another.

C) They always result in a 9:7 ratio of a dihybrid cross.

Producing wild-type offspring from a cross between parents that both display the same recessive phenotype illustrates:

A) Complementation

B) Epistasis

C) Pleiotropy

D) Codominance

A) Complementation

The multiple effects of a single gene on an organism's phenotype are called:

A) Epistasis

B) Pleiotropy

C) Codominance

D) Complementation

B) Pleiotropy

A allele is the most prevalent in a population and usually encodes a normally functioning protein.

A) Mutant

B) Wild-type

C) Lethal

D) Recessive

B) Wild-type

In overdominance, the genotype is beneficial over the genotypes.

A) Homozygous, heterozygous

B) Heterozygous, homozygous

C) Dominant, recessive

D) Recessive, dominant

B) Heterozygous, homozygous

In cattle, scurs follow a sex-influenced pattern. A heterozygous male has and a heterozygous female has .

A) Scurs, no scurs

B) No scurs, scurs

C) Scurs, scurs

D) No scurs, no scurs

A) Scurs, no scurs

If a combination of two or more genes is required to produce a specific trait, it is called a(n):

A) Pleiotropy

B) Gene interaction

C) Single gene trait

D) Lethal mutation

B) Gene interaction

Coat color in rodents involving a gene interaction between two genes producing three phenotypes involves:

A) A gene modifier effect

B) Complementation only

C) Pleiotropy

D) Codominance

A) A gene modifier effect

The presence of a group of antigens determining blood type occurs as a result of a:

A) Single gene with two alleles

B) Multiple allele system

C) Lethal allele system

D) Sex-linked trait

B) Multiple allele system

Crossing an eosin-eyed male Drosophila to a homozygous red-eyed female results in what offspring phenotype?

A) All offspring will have red eyes.

B) All offspring will have eosin eyes.

C) ½ red, ½ eosin eyes.

D) ¾ red, ¼ eosin eyes.

A) All offspring will have red eyes.

Heavy metal concentration effects studied across genetically identical organisms evaluate a:

A) Norm of reaction

B) Mendelian ratio

C) Lethal dose

D) Pedigree chart

A) Norm of reaction

Achondroplasia is a dominant dwarfism trait where two dominant alleles are lethal. What is the probability of a non-dwarf child from two achondroplasia parents?

A) 1/4

B) 1/3

C) 1/2

D) 2/3

B) 1/3

For an X-linked dominant disorder pedigree, what is the probability of individual III-2 being born male and affected?

A) 0

B) 1/4

C) 1/2

D) 1

A) 0

For an X-linked dominant disorder pedigree, what is the probability of individual III-2 being born female and affected?

A) 0

B) 1/4

C) 1/2

D) 1

C) 1/2

Gout is a sex-influenced trait (dominant in males, recessive in females). If a heterozygous male with gout and a heterozygous female without mate, what proportion of male offspring will not have gout?

A) 0%

B) 25%

C) 50%

D) 75%

B) 25%

Crossing a rare purple plumed parrot with a true breeding white parrot gives white and purple. Crossing two purple parrots gives white and purple. Why?

A) The purple allele is lethal in the homozygous state.

B) It follows simple recessive inheritance.

C) It is an X-linked trait.

D) Codominance is at play.

A) The purple allele is lethal in the homozygous state.

Crossing a rose comb chicken with a pea comb chicken yields all walnut. F1 cross yields 9:3:3:1 ratio. What explains this?

A) Simple monohybrid cross

B) walnut = R_P, single = rrpp, rose = R_pp, pea = rrP

C) Lethal gene interaction

D) Incomplete dominance

B) walnut = R_P, single = rrpp, rose = R_pp, pea = rrP