Question 1

Individuals with neurofibromatosis may have a range of phenotypes,from pigment spots on the skin to tumorlike growths.This is an example of
A)incomplete penetrance.
B)variable expressivity.
C)age of onset.
D)X-inactivation.
E)gene magnification.

Accepted Answer

Neurofibromatosis exhibiting a range of phenotypes indicates variable expressivity, where the same genotype leads to different phenotypes in different individuals.

Question 2

Familial hypercholesterolemia is a genetic disease that affects approximately one in 500 people worldwide.There is more than one genetic cause of the disease.Class I is often described as an autosomal dominant disease.Affected individuals have cholesterol levels >250 as children and often >300 as adults.However,homozygotes have cholesterol levels of >600 as children and can die of heart attacks in their 20s.These individuals entirely lack a functional LDL receptor.Which of the following would be the best description of the inheritance of this form of hypercholesterolemia?
A)Dominant epistatic
B)Codominant
C)Incompletely dominant
D)Complementary
E)Recessive epistatic

Accepted Answer

Incompletely dominant

Question 3

Two true-breeding mutant strains of Drosophila have black body color instead of the wild-type gray yellow.When the two strains are crossed,all the F₁ flies have wild-type body color.How can these data be interpreted? A)Recombination occurred. B)Complementation occurred. C)The mutations involved are on two different genes. D)A new mutation occurred in all the offspring. E)Both B and C

Accepted Answer

Complementation occurs when two different mutations in the homozygous state for each mutant parent complement each other in the heterozygous offspring, resulting in a wild-type phenotype. This implies that the mutations are in different genes, which is why both B and C are correct.

Question 4

Dextral (D) and sinistral (d) shell coiling in the water snail Limnaea peregra is genetically determined. From a population of mixed sinistral and dextral snails, a sinistral female and a dextral male are chosen. All the offspring are dextral. When the female offspring are mated, 50% produce only sinistral snails and the other 50% produce only dextral snails.
-This form of inheritance is called
A)maternal inheritance.
B)sex-limited inheritance.
C)sex-linked inheritance.
D)maternal effect.
E)partial penetrance.

Accepted Answer

The inheritance pattern described is an example of maternal effect, where the phenotype of the offspring is determined by the genotype of the mother, regardless of the offspring's own genotype. In this case, the phenotype (shell coiling direction) of the offspring is determined by the genotype of the mother snail.

Question 5

The distinctive fur pattern of Siamese cats results when genes that are responsible for the coat color are influenced by
A)age.
B)X-inactivation.
C)gender.
D)temperature.
E)other genes.

Accepted Answer

The distinctive fur pattern of Siamese cats results from a temperature-sensitive gene that affects pigment production. This means that the areas of the cat's body that are cooler have darker fur, while warmer areas have lighter fur. This pattern becomes visible as the kittens grow and develop, and it is not influenced by age, gender, X-inactivation, or other genes.

Question 6

A person with type B blood could safely receive a transfusion of blood from someone with blood type
A)B.
B)AB.
C)O.
D)Both A and C
E)Any of these

Accepted Answer

A person with type B blood has B antigens on their red blood cells and anti-A antibodies in their plasma. They can safely receive blood from donors who also have B antigens (i.e. blood type B) and from donors with type O blood, as type O blood does not have A or B antigens that can trigger an immune response. Therefore, options A and C are correct. However, they cannot receive blood from someone with type AB blood as AB blood has both A and B antigens on their red blood cells, which will trigger the type B recipient's immune response.

Question 7

Which of the following will result in modifications to the expected Mendelian ratios?
A)Epistasis
B)Incomplete dominance
C)Incomplete penetrance
D)Gene interaction
E)All of these

Accepted Answer

All of the listed factors can result in modifications to the expected Mendelian ratios. Epistasis occurs when one gene masks or affects the expression of another, leading to altered ratios. Incomplete dominance results in a blending of traits, also leading to modified ratios. Incomplete penetrance describes the situation where individuals carry a gene but do not express it, leading to ratios that differ from the expected. Gene interaction occurs when multiple genes interact to produce a phenotype, leading to modified ratios as well.

Question 8

In the multiple allelic system for eye color in Drosophila,the phenotypic expression of the alleles depends on
A)how much pigment is produced by the alleles present.
B)the interaction of alleles from two different genes.
C)the temperature at which the flies are grown.
D)the sex of the fly.
E)Both A and B

Accepted Answer

The phenotypic expression of the alleles in the multiple allelic system for eye color in Drosophila depends on how much pigment is produced by the alleles present. This is determined by the function of the genes carried by these alleles in producing the pigments responsible for eye color.

Question 9

Mutants that make up a complementation group complement each other.

Accepted Answer

Mutants that make up a complementation group do not complement each other; they fail to produce a wild-type phenotype when combined, indicating they affect the same gene or functional pathway.

Question 10

Solid black,black with tan belly,and agouti coat color in mice are all caused by alleles of the agouti gene.All three colors can be true-breeding.When using mice from true-breeding strains: (1)Black × Agouti F₁s are all agouti,(2)Black × Black with Tan belly F₁s are all black and tan,and (3)Black with Tan belly × Agouti F₁s are all agouti.If you were to cross the F₁s from (1)with the F₁s from (2),what proportion of the resulting offspring would you expect to be black with a tan belly? A)None B) $\frac { 1 } { 4 }$ C) $\frac { 3 } { 16 }$ D) $\frac { 1 } { 2 }$ E) $\frac { 1 } { 16 }$

Accepted Answer

The F1s from (1) are all heterozygous for the agouti gene (Aa). The F1s from (2) are also all heterozygous for the agouti gene (Aa). When these two F1s are crossed, the resulting offspring will be in the following proportions:1/4 AA (black)1/4 Aa (agouti)1/4 aa (black with tan belly)1/4 Aa (agouti)Therefore, the proportion of offspring that would be expected to be black with a tan belly is 1/4.

Question 11

Studies performed on identical twins separated at birth have shown that many phenotypes,such as IQ or alcoholism,are influenced by the person's genotype as well as by their environment.

Accepted Answer

Studies on identical twins separated at birth have shown that many phenotypes are influenced by both genotype and environment, indicating the role of nature and nurture in shaping human characteristics.

Question 12

For a gene with complete dominance,the recessive allele has no effect on the phenotype of a heterozygote.

Accepted Answer

In complete dominance, the dominant allele masks the recessive allele, resulting in the same phenotype for both homozygous dominant and heterozygous individuals. The recessive allele has no effect on the phenotype of a heterozygote.

Question 13

People affected by diseases caused by mtDNA defects
A)typically have cells that are heteroplasmons.
B)show partial penetrance.
C)are sterile.
D)inherited them through maternal effect.
E)have epistatic respiration.

Accepted Answer

Mitochondrial DNA (mtDNA) is inherited maternally, and individuals with mtDNA defects often have cells that are heteroplasmons, meaning they contain a mixture of normal and mutant mtDNA.

Question 14

Two persons who have recessive genetic deafness marry and have 6 children.All the children can hear.The reason they can hear is most likely due to
A)epistasis.
B)pleiotropy.
C)sex linkage.
D)complementation.
E)partial penetrance.

Accepted Answer

The most likely reason that all the children can hear even though their parents have recessive genetic deafness is due to complementation. This means that the deafness in the parents is caused by mutations in different genes, and the deafness phenotype is only expressed when both mutations are present. Since each child inherits a different combination of these recessive alleles, none of them have the combination that would cause deafness. This phenomenon is also known as "genetic complementation."

Question 15

A and B antigens in human blood are produced by the conversion of ________ by the addition of a sugar group.
A)anti-A and anti-B antibodies
B)the H antigen
C)hemoglobin
D)α-N-acetylgalactosamine
E)anti-O antibodies

Accepted Answer

The A and B antigens in human blood are produced by the conversion of the H antigen through the addition of specific sugar groups. The A antigen is created by adding N-acetylgalactosamine to the H antigen, while the B antigen is formed by adding another sugar, galactose, to the H antigen. This process is enzyme-mediated and determines an individual's blood type in the ABO blood group system.

Question 16

Dextral (D) and sinistral (d) shell coiling in the water snail Limnaea peregra is genetically determined. From a population of mixed sinistral and dextral snails, a sinistral female and a dextral male are chosen. All the offspring are dextral. When the female offspring are mated, 50% produce only sinistral snails and the other 50% produce only dextral snails.
-What were the genotypes of the sinistral female and dextral male that were initially chosen?
A)dd female and Dd male
B)Dd female and dd male
C)dd female and DD male
D)DD female and dd male
E)Dd female and Dd male

Accepted Answer

The fact that all the offspring from the mating of a sinistral female and a dextral male are dextral suggests that the dextral trait is dominant over sinistral trait. This means that the male must be heterozygous for the dextral trait (Dd) while the female could be either homozygous for the sinistral trait (dd) or heterozygous (Dd). If the female was homozygous for the sinistral trait (dd), then all the offspring from the second mating of the female offspring would also be sinistral but this is not what is observed. Therefore, it is likely that the female was heterozygous for the sinistral trait (Dd) and the male was heterozygous for the dextral trait (Dd).

Question 17

Comb shape in chickens is controlled by
A)the interaction of three alleles and codominance,resulting in four different phenotypes.
B)one gene with incomplete dominance,resulting in three different phenotypes.
C)the epistatic interaction of two genes,resulting in two different phenotypes.
D)the interaction of two genes with complete dominance,resulting in four different phenotypes.
E)None of these

Accepted Answer

The comb shape in chickens is indeed controlled by the interaction of two genes, each exhibiting complete dominance, and this genetic interaction results in four distinct phenotypes. This is a classic example of how genes can interact in a non-additive manner to produce various phenotypes.

Question 18

Manx cats have no tails.When two Manx cats are bred together there is always a one third chance that a kitten will have a tail.When a Manx cat is bred to a cat with a normal tail there is a one-half chance that a kitten will have a tail.Which of the following is the best explanation for this?
A)The Manx genotype exhibits variable expression.
B)The Manx phenotype is dominant,but the allele is a recessive lethal.
C)The Manx phenotype is dominant epistatic.
D)The Manx phenotype is caused by gene interactions.
E)The Manx phenotype is a result of heteroplasmy.

Accepted Answer

The fact that a Manx cat bred with a normal-tailed cat has a 50% chance of producing kittens with tails suggests that the Manx phenotype is dominant. However, the fact that breeding two Manx cats together can result in a kitten with a tail suggests that the allele is recessive lethal, meaning that homozygous Manx cats do not survive to birth. Therefore, the Manx phenotype is dominant, but the allele is a recessive lethal.

Question 19

An allele that exhibits incomplete dominance is usually haplosufficient.

Accepted Answer

The answer of An allele that exhibits incomplete dominance is...

Question 20

Human height is a trait affected by both genes and the environment.How is this so?

Accepted Answer

The answer of Human height is a trait affected by...

Quiz 13: Extensions of and Deviations From Mendelian Genetic Principles

Individuals with neurofibromatosis may have a range of phenotypes,from pigment spots on the skin to tumorlike growths.This is an example of

Two true-breeding mutant strains of Drosophila have black body color instead of the wild-type gray yellow.When the two strains are crossed,all the F1 flies have wild-type body color.How can these data be interpreted?

The distinctive fur pattern of Siamese cats results when genes that are responsible for the coat color are influenced by

A person with type B blood could safely receive a transfusion of blood from someone with blood type

Which of the following will result in modifications to the expected Mendelian ratios?

In the multiple allelic system for eye color in Drosophila,the phenotypic expression of the alleles depends on

Mutants that make up a complementation group complement each other.

Studies performed on identical twins separated at birth have shown that many phenotypes,such as IQ or alcoholism,are influenced by the person's genotype as well as by their environment.

For a gene with complete dominance,the recessive allele has no effect on the phenotype of a heterozygote.

People affected by diseases caused by mtDNA defects

Two persons who have recessive genetic deafness marry and have 6 children.All the children can hear.The reason they can hear is most likely due to

A and B antigens in human blood are produced by the conversion of ________ by the addition of a sugar group.

Comb shape in chickens is controlled by

Manx cats have no tails.When two Manx cats are bred together there is always a one third chance that a kitten will have a tail.When a Manx cat is bred to a cat with a normal tail there is a one-half chance that a kitten will have a tail.Which of the following is the best explanation for this?

An allele that exhibits incomplete dominance is usually haplosufficient.

Human height is a trait affected by both genes and the environment.How is this so?

Two true-breeding mutant strains of Drosophila have black body color instead of the wild-type gray yellow.When the two strains are crossed,all the F₁ flies have wild-type body color.How can these data be interpreted?