Deck 13: Extensions of and Deviations From Mendelian Genetic Principles

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.

Answer 1

B

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

Answer 2

C

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

Answer 3

E

Question 4

This form of inheritance is called

A)maternal inheritance.
B)sex-limited inheritance.
C)sex-linked inheritance.
D)maternal effect.
E)partial penetrance.

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.

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

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

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

Question 9

Mutants that make up a complementation group complement each other.

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) $\frac { 1 } { 16 }$

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.

Question 12

For a gene with complete dominance,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.

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.

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

Question 16

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

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

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.

Question 19

An allele that exhibits incomplete dominance is usually haplosufficient.

Question 20

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

Question 21

Sex-limited traits are caused by genes that are on sex chromosomes.

Question 22

What is the cause of Tay-Sachs disease?

Question 23

For a gene with multiple alleles,what is the maximum number of alleles that a diploid organism may have?

Question 24

How could a man with blood type A and a woman with blood type B produce a child with blood type O?

Question 25

In a dihybrid cross with independent assortment of the two genes,any deviation from the Mendelian 9:3:3:1 ratio indicates that the phenotype is the product of the interaction of two or more genes.

Question 26

In the human ABO blood system,the allele i is dominant to I^A and I^B.

Question 27

Explain and differentiate among the molecular bases of codominance,incomplete dominance,and complete dominance.

Question 28

Use a Punnett square to demonstrate a cross between two of the F₁ offspring.What are the phenotypes and ratios that occur?

Question 29

Phenylketonuria (PKU)is an example of a phenotype that is solely influenced by genes.

Question 30

Recessive lethals are often mutations in essential genes.

Question 31

What is the number of possible genotypes in a multiple allele series with 6 alleles? How many of these are homozygous and how many are heterozygous?

Question 32

In a genotype with complete penetrance,less than 100% of individuals with a particular genotype exhibit the expected phenotype.

Question 33

Generally,blue eyes are recessive to dark brown eyes in humans.Individuals with albinism typically have blue eyes with a strong red reflection.A blue-eyed woman with albinism marries a man who is blue-eyed but does not have albinism.All their children have dark brown eyes.How can this be explained?

Question 34

What is the phenotype and genotype of the chicks?

Question 35

In chickens,there is a mutant gene called "frizzle" that results in weak,stringy,and easily broken feathers.When a frightfully frizzled fowl is bred to a normal chicken,the offspring are all mildly frizzled.If one breeds two mildly frizzled chickens to each other,the offspring have the phenotypic ratio of 1 normal: 2 mildly frizzled: 1 frightfully frizzled.What is the mode of inheritance of "frizzle"?

Question 36

In cats,the dominant white gene (W)may or may not also cause deafness.Homozygotes are more likely to be deaf than heterozygotes.If you breed heterozygous white cats together and produce 100 kittens,how many would you expect to be deaf if all the proportions came out perfectly? Assume that heterozygotes have an 8% chance of being deaf,and homozygotes a 60% chance of being deaf.

Question 37

Why is it that human males and females who are both heterozygous for the pattern-baldness gene have different phenotypes (males are bald,females are not bald)?

Question 38

In the ABO blood-type system,which genotypes could confer type A blood to a person?

Question 39

Comb shape in chickens also involves the interaction of two genes,but the F₂ generation shows a typical 9:3:3:1 Mendelian ratio.How does this work?

Question 40

The 9:6:1 F₂ ratio found in fruit shape in summer squash is a deviation from an expected Mendelian ratio.What does this represent?