Question 1

An autosomal recessive disorder
A) requires that only one parent be a carrier.
B) displays its symptoms in heterozygotes.
C) is more frequent in males than females.
D) requires that both parents are carriers.
E) only affects females.

Accepted Answer

An autosomal recessive disorder requires that both parents are carriers because they must each contribute a recessive allele for the disorder to be expressed in their offspring.

Question 2

A couple have a child with Tay-Sachs disease.What is (are)their genotype(s)?
A) both are heterozygous
B) one is homozgous dominant and the other is homozgous recessive
C) both are homozygous dominant
D) both are homozygous recessive
E) more than one of these is possible

Accepted Answer

Tay-Sachs disease is an autosomal recessive disorder, so both parents must be carriers (heterozygous) to have a child with the disease.

Question 3

Males more commonly are affected by X-linked recessive genetic disorders than are females because
A) females have two X chromosomes and thus less of a chance to be recessive.
B) males have only one X and thus more of a chance to be recessive.
C) males have only one X, they have multiple alleles for each gene.
D) Y chromosomes cause X gene mutations.
E) males are weaker genetically than females.

Accepted Answer

Because males have only one X chromosome, they have a higher chance of inheriting and expressing any recessive genes located on it. Females have two X chromosomes, so they have a backup copy in case one X chromosome has a recessive mutation.

Question 4

The probability of producing a normal child by two parents who are carriers for an autosomal recessive disorder is
A) 50 percent.
B) 0 percent.
C) 100 percent.
D) 25 percent.
E) 75 percent.

Accepted Answer

When both parents are carriers for an autosomal recessive disorder, there is a 25% chance the child will be affected, a 50% chance the child will be a carrier, and a 25% chance the child will be unaffected and not a carrier. Therefore, the probability of producing a normal (unaffected and not a carrier) child is 25% + 50% = 75%.

Question 5

What could the children of a color-blind woman and a man with normal vision be?
A) All will be color-blind.
B) None will be color-blind.
C) Daughters will be color-blind, and sons will be normal.
D) Sons will be color-blind, and daughters will be normal.
E) About half would be color-blind.

Accepted Answer

Color blindness is often X-linked recessive. A color-blind woman (XcXc) and a man with normal vision (XY) will have sons who inherit the Xc from their mother, making them color-blind (XcY), and daughters who inherit the normal X from their father, making them carriers but not color-blind (XcX).

Question 6

In Hutchinson-Gilford progeria,which organelle is affected?
A) lysosomes
B) mitochondria
C) Golgi bodies
D) nuclei
E) rough endoplasmic reticula

Accepted Answer

In Hutchinson-Gilford progeria, the nuclei of affected cells are affected. There is a mutation in the Lamin A/C gene, which leads to the production of a truncated and abnormal form of the lamin A protein called progerin. Progerin accumulates in the nuclei and disrupts the normal structure and function of the nuclear envelope, causing premature aging symptoms.

Question 7

If a daughter expresses an X-linked recessive gene,she inherited the trait from
A) her mother.
B) her father.
C) both parents.
D) neither parent.
E) her grandmother.

Accepted Answer

The answer of If a daughter expresses an X-linked recessive...

Question 8

In a family pedigree of several generations,it is found that freckles appear in every generation and affect both sexes equally.Freckles is most likely a _____ trait.
A) dominant
B) recessive
C) X-linked
D) epistatic
E) pleiotrophic

Accepted Answer

Freckles appearing in every generation and affecting both sexes equally suggests it is a dominant trait, as dominant traits typically do not skip generations and are not sex-linked.

Question 9

An X-linked carrier is a
A) homozygous dominant female.
B) heterozygous female.
C) homozygous recessive female.
D) homozygous male.
E) heterozygous male.

Accepted Answer

An X-linked carrier is a female who carries one copy of an X-linked gene mutation on one of her two X chromosomes. She is heterozygous for the gene mutation, meaning she has one normal X chromosome and one X chromosome with the mutation. Males cannot be carriers of X-linked traits because they only have one X chromosome.

Question 10

George is a normal XY boy.Who among the following would essentially have the same Y chromosome as George?
A) his father's brother
B) his mother's father
C) his mother's brother
D) his father's father
E) more than one of these is possible but only those who are related to his father

Accepted Answer

The answer of George is a normal XY boy.Who among...

Question 11

Albinism is a recessive disorder.Rapinder is an albino and his partner,Janeen has normal pigmented skin.Her father was also an albino.Janeen is pregnant and Rapinder is the father.What is the probability that they will have normal pigmented child?
A) 0%
B) 25%
C) 50%
D) 75%
E) 100%

Accepted Answer

Janeen is a carrier of the albinism gene (Aa) since her father was an albino (aa). Rapinder is an albino (aa). The possible genotypes for their child are Aa (normal pigmented) and aa (albino), giving a 50% chance of normal pigmentation.

Question 12

Ella is a normal XX girl who is red-green colorblind.She is pregnant and the father is Terrick who has normal color vision.What is the probability that - if they have a daughter - the daughter will be red-green colorblind?
A) 0%
B) 25%
C) 50%
D) 100%
E) impossible to tell with the information provided

Accepted Answer

Red-green colorblindness is an X-linked recessive trait. Ella, being colorblind, has two X chromosomes with the colorblind allele (XcXc). Terrick, having normal vision, has one normal X chromosome and one Y chromosome (XY). A daughter would inherit one X chromosome from each parent, so she would receive one Xc from Ella and one normal X from Terrick, making her a carrier (XcX) but not colorblind.

Question 13

Why are most X-linked disorders recessive?
A) X-linked dominant disorders are always fatal to females
B) females only have one active X- dominant disorders would render them sterile
C) dominant X-linked disorders are almost always fatal to the male embryo
D) dominant X-linked disorders, regardless of their overall effect, prevent proper sperm formation
E) more than one of these is the reason why most X-linked disorders are fatal

Accepted Answer

X-linked dominant disorders can be more severe in males because they have only one X chromosome, and if the disorder is severe, it can lead to lethality in male embryos. This is why most X-linked disorders are recessive, as they allow males to survive with one normal allele.

Question 14

In Tay-Sachs disease,which organelle is affected?
A) lysosomes
B) mitochondria
C) Golgi bodies
D) nuclei
E) rough endoplasmic reticula

Accepted Answer

Tay-Sachs disease is a lysosomal storage disorder that affects the function of lysosomes in breaking down cellular waste material. As a result, there is an accumulation of a fatty substance called GM2 ganglioside in the cells of the brain and nerve tissue, leading to progressive neurological deterioration.

Question 15

A boy inherits his X chromosome from
A) his father.
B) his mother.
C) either his father or his mother.
D) both his father and his mother.

Accepted Answer

A boy inherits his X chromosome from his mother. This is because females have two X chromosomes, while males have one X and one Y chromosome. During fertilization, the mother can only pass down one of her X chromosomes to her son, while the father can pass down either his X or Y chromosome. Therefore, the X chromosome inherited by a male child can only come from his mother.

Question 16

In an autosomal dominant disorder such as Huntington's,two carrier parents have the probability of passing the gene on to ____ percent of their children.
A) 50
B) 0
C) 100
D) 25
E) 75

Accepted Answer

The answer of In an autosomal dominant disorder such as...

Question 17

In a family pedigree that followed several generations,Gaucher's disease was found in family members every other generation and equally in males and females.Gaucher's disease is most likely a ______ disease.
A) dominant
B) recessive
C) X-linked
D) epistatic
E) pleiotrophic

Accepted Answer

Gaucher's disease is a recessive disease, meaning that an individual must inherit two copies of the mutated gene (one from each parent) to develop the disease. The fact that the disease is found every other generation and equally in males and females suggests that it follows a pattern of autosomal recessive inheritance.

Question 18

Which of the following is NOT a single gene trait?
A) cleft chin
B) attached earlobes
C) dimples
D) red hair
E) brown skin

Accepted Answer

Brown skin is a polygenic trait, meaning it is controlled by multiple genes instead of just one. The other options listed are all single gene traits.

Question 19

Which of the following would be considered a carrier of a sex-linked recessive defect?
A) a man with the defect
B) a woman with the defect
C) a father of a son with the defect
D) the normal daughter whose father had the defect
E) a son of two unaffected parents

Accepted Answer

The answer of Which of the following would be considered...

Question 20

Huntington's disease is a dominant autosomal genetic disorder.Albert has Huntington's disease as did his mother.His father was normal.Albert is married to Lydia who does not have Huntington's disease.If Albert and Lydia have a child,what is the probability that their child will have Huntington's disease?
A) 0%
B) 25%
C) 50%
D) 75%
E) 100%

Accepted Answer

Since Huntington's disease is a dominant autosomal genetic disorder and Albert has the disease, he must have inherited one copy of the mutated gene from his affected mother. This means that he could pass on the disease-causing gene to his offspring with a probability of 50%. Since Lydia does not have Huntington's disease, she definitely does not have the disease-causing gene to pass on. Therefore, the probability of their child inheriting the gene from Albert is 50%.

Quiz 9: Patterns of Inheritance

An autosomal recessive disorder

A couple have a child with Tay-Sachs disease.What is (are) their genotype(s) ?

Males more commonly are affected by X-linked recessive genetic disorders than are females because

The probability of producing a normal child by two parents who are carriers for an autosomal recessive disorder is

What could the children of a color-blind woman and a man with normal vision be?

In Hutchinson-Gilford progeria,which organelle is affected?

If a daughter expresses an X-linked recessive gene,she inherited the trait from

In a family pedigree of several generations,it is found that freckles appear in every generation and affect both sexes equally.Freckles is most likely a _____ trait.

An X-linked carrier is a

George is a normal XY boy.Who among the following would essentially have the same Y chromosome as George?

Albinism is a recessive disorder.Rapinder is an albino and his partner,Janeen has normal pigmented skin.Her father was also an albino.Janeen is pregnant and Rapinder is the father.What is the probability that they will have normal pigmented child?

Ella is a normal XX girl who is red-green colorblind.She is pregnant and the father is Terrick who has normal color vision.What is the probability that - if they have a daughter - the daughter will be red-green colorblind?

Why are most X-linked disorders recessive?

In Tay-Sachs disease,which organelle is affected?

A boy inherits his X chromosome from

In an autosomal dominant disorder such as Huntington's,two carrier parents have the probability of passing the gene on to ____ percent of their children.

In a family pedigree that followed several generations,Gaucher's disease was found in family members every other generation and equally in males and females.Gaucher's disease is most likely a ______ disease.

Which of the following is NOT a single gene trait?

Which of the following would be considered a carrier of a sex-linked recessive defect?