Question 1

If the characteristic followed in the pedigree is autosomal recessive, what is III-1's genotype? 
A) either homozygous dominant or heterozygous
B) definitely heterozygous
C) definitely homozygous dominant
D) must be homozygous recessive
E) homozygous dominant since he is a male but a female would be heterozygous

Accepted Answer

B

Question 2

Which description of a Y-linked trait in humans is CORRECT?
A) All the sons of an affected father will be affected with the trait.
B) Half the sons of a mother whose father was affected with the trait will be affected.
C) Half the sons of an affected father will not be affected with the trait and the other half will be infertile.
D) All the daughters of an affected father will be phenotypically normal but half of their own sons will be affected with the trait.
E) The parents of an affected man likely were both phenotypically normal.

Accepted Answer

A

Question 3

What is/are the possible inheritance pattern(s) for the characteristic in Pedigree 1? Assume no new mutations and complete penetrance. 
A) autosomal recessive only
B) autosomal dominant only
C) X-linked recessive only
D) X-linked dominant only
E) All of these are possible.

Accepted Answer

A

Question 4

Most pedigrees showing the hypothetical human trait show the following characteristics: 
• Females are affected twice as frequently as males.
• Affected fathers may have affected daughters but never affected sons.
• Half the children of affected mothers and normal fathers are affected.
What is the MOST likely mode of inheritance for this disorder?
A) autosomal recessive
B) autosomal dominant
C) X-linked recessive
D) X-linked dominant
E) Y-linked

Accepted Answer

The trait is likely X-linked dominant because it affects females more frequently, affected fathers can pass it to daughters but not sons, and affected mothers have a 50% chance of passing it to their children.

Question 5

Most pedigrees showing the hypothetical human trait show the following characteristics: 
• Males and females are equally affected.
• Two unaffected parents can have an affected child.
• In families in which the parents are unaffected but the children are affected, one-fourth of the children are affected.
What is the MOST likely mode of inheritance for this disorder?
A) autosomal recessive
B) autosomal dominant
C) X-linked recessive
D) X-linked dominant
E) Y-linked

Accepted Answer

The characteristics described are consistent with an autosomal recessive inheritance pattern, where the trait can appear in both males and females equally, unaffected parents can have affected children, and approximately one-fourth of the children are affected if both parents are carriers.

Question 6

Could the characteristics followed in the pedigree be caused by an X-linked recessive allele? 
A) Yes, all individuals fit the X-linked recessive inheritance pattern.
B) No, the offspring of I-1 and I-2 contradict an X-linked recessive inheritance.
C) No, the offspring of I-3 and I-4 contradict an X-linked recessive inheritance.
D) No, the offspring of II-3 and II-4 contradict an X-linked recessive inheritance.
E) Possibly, but I-4 would have to be a heterozygous carrier if there is X-linked inheritance.

Accepted Answer

The answer of Could the characteristics followed in the pedigree...

Question 7

Could the characteristic followed in the pedigree below be caused by an autosomal dominant disease? Why or why not? 
A) Yes, all individuals fit the autosomal dominant inheritance pattern.
B) No, the offspring of I-1 and I-2 contradict an autosomal dominant inheritance.
C) No, the offspring of I-3 and I-4 contradict an autosomal dominant inheritance.
D) No, the offspring of II-3 and II-4 contradict an autosomal dominant inheritance.
E) Yes, the offspring of I-1and I-2 are consistent with an autosomal dominant inheritance pattern.

Accepted Answer

The answer of Could the characteristic followed in the pedigree...

Question 8

In pedigree analysis, consanguinity refers to:
A) mating between two heterozygous carrier parents.
B) the realization that phenotypes between children and grandparents are often more closely related than between children and parents.
C) mating between two closely related parents.
D) a situation where the children of two parents are adopted.
E) a situation where only one individual in the entire pedigree is affected with the trait or disorder.

Accepted Answer

Consanguinity refers to the mating between two closely related individuals, which increases the probability of offspring inheriting genetic disorders.

Question 9

In pedigree analysis, the proband is:
A) the individual having the trait or disorder from whom the pedigree is initiated.
B) the medical geneticist who analyzes the pedigree to find the mode of inheritance for the disorder.
C) the parents of the first child in the family to show the trait or disorder.
D) one of the grandparents or great grandparents who are in the first generation of the pedigree.
E) the most common software package that geneticists use to analyze pedigrees.

Accepted Answer

The proband is the individual having the trait or disorder from whom the pedigree is initiated. This person is the starting point for geneticists to trace the inheritance pattern of the trait or disorder within the family.

Question 10

The ability to roll the tongue is caused by a dominant allele. A woman is a "roller," but one of her parents is not. The woman is expecting a child with a man who is a "nonroller." What is the probability that their first child will be a "roller"?
A) 1/4
B) 0
C) 3/4
D) 1/2
E) 1

Accepted Answer

The woman must be heterozygous (Rr) because she is a roller but has a nonroller parent (rr). The man is a nonroller (rr). The possible genotypes for their child are Rr (roller) and rr (nonroller), giving a 1/2 probability of being a roller.

Question 11

If the characteristic followed in the pedigree is X-linked recessive allele, what is III-1's genotype? 
A) hemizygous for a dominant allele
B) hemizygous for a recessive allele
C) definitely heterozygous
D) definitely homozygous dominant
E) either heterozygous or homozygous dominant

Accepted Answer

The answer of If the characteristic followed in the pedigree...

Question 12

Two parents are phenotypically normal, but one of their four biological children has a typical autosomal recessive trait. The other three children are phenotypically normal. It is very likely that:
A) the affected child is a girl.
B) the affected child is a boy.
C) the trait was expressed by one of the grandparents of the children.
D) the parents are both heterozygous for the trait.
E) if the affected child eventually marries a phenotypically normal spouse, all of their children will have the trait.

Accepted Answer

For an autosomal recessive trait to be expressed, both parents must be carriers (heterozygous) for the trait, meaning they each have one recessive allele.

Question 13

Which statement is INCORRECT concerning an X-linked recessive trait in humans?
A) An affected man often has phenotypically normal parents.
B) All the sons of an affected woman will be expected to be affected.
C) An affected woman almost always has an affected mother.
D) An affected man usually has a mother who carries the recessive allele.
E) A phenotypically normal woman whose father was affected is likely to be heterozygous for the condition.

Accepted Answer

An affected woman almost always has an affected mother is incorrect because an affected woman can have a carrier mother and an affected father, not necessarily an affected mother.

Question 14

If the pedigree below is for an autosomal recessive characteristic, which individuals are definitely heterozygous? 
A) I-1, I-2, II-2, II-4, II-5
B) I-1, I-2, I-4, III-1
C) I-1, I-2, II-4, II-5, III-1
D) II-2, II-4, II-5, II-3
E) II-2, II-4, II-5, III-1

Accepted Answer

The answer of If the pedigree below is for an...

Question 15

Most pedigrees showing the hypothetical human trait show the following characteristics: 
• If a phenotypically normal woman with an affected father has children with an unaffected man, half of the sons and none of the daughters are affected.
• Affected females always have an affected father and an affected maternal grandfather.
• The trait is never passed from father to son.
What is the MOST likely mode of inheritance for this disorder?
A) autosomal recessive
B) autosomal dominant
C) X-linked recessive
D) X-linked dominant
E) Y-linked

Accepted Answer

The trait is X-linked recessive because it is never passed from father to son, affected females have affected fathers, and half of the sons of carrier females are affected.

Question 16

Most pedigrees showing the hypothetical human trait show the following characteristics:
 • Only males are affected.
• Affected fathers always pass the trait to sons.
What is the MOST likely mode of inheritance for this disorder?
A) autosomal recessive
B) autosomal dominant
C) X-linked recessive
D) X-linked dominant
E) Y-linked

Accepted Answer

The trait is likely Y-linked because it only affects males and is passed directly from father to son, which is characteristic of Y-linked inheritance.

Question 17

Which of the following is NOT a characteristic of X-linked recessive traits in humans?
A) More males than females are affected.
B) Approximately one-half of the sons of a female carrier are affected.
C) They cannot be passed from father to son.
D) Phenotypically normal daughters of affected men are always carriers.
E) Affected daughters always have an affected mother.

Accepted Answer

X-linked recessive traits can be passed from an affected father to a daughter if the mother is a carrier, so affected daughters do not always have an affected mother.

Question 18

Which term refers to mating between closely related people?
A) consanguinity
B) probanding
C) congenital
D) concordance
E) discordance

Accepted Answer

Consanguinity refers to the genetic relationship between individuals who share a common ancestor, often used to describe mating between closely related people.

Question 19

Which of the following is NOT a typical characteristic of human traits that follow an autosomal recessive inheritance pattern?
A) They often "skip" generations.
B) They appear equally in males and females.
C) Parents of affected children are often phenotypically normal themselves.
D) When affected individuals marry phenotypically normal individuals, their children are often phenotypically normal.
E) All of the above are characteristic of autosomal recessive inheritance.

Accepted Answer

All the listed characteristics are typical of autosomal recessive inheritance patterns.

Question 20

The ability to roll the tongue is caused by a dominant allele. A woman is a "roller," but one of her parents is not. What is the woman's genotype?
A) homozygous dominant
B) heterozygous
C) homozygous recessive
D) either homozygous recessive or homozygous dominant
E) It cannot be determined from this information.

Accepted Answer

The woman must be heterozygous because she is a roller (has the dominant trait) but has a non-roller parent (who must be homozygous recessive). Therefore, she must have inherited one dominant allele from the roller parent and one recessive allele from the non-roller parent.

Quiz 6: Pedigree Analysis, Applications, and Genetic Testing

If the characteristic followed in the pedigree is autosomal recessive, what is III-1's genotype?

Which description of a Y-linked trait in humans is CORRECT?

What is/are the possible inheritance pattern(s) for the characteristic in Pedigree 1? Assume no new mutations and complete penetrance.

Could the characteristics followed in the pedigree be caused by an X-linked recessive allele?

Could the characteristic followed in the pedigree below be caused by an autosomal dominant disease? Why or why not?

In pedigree analysis, consanguinity refers to:

In pedigree analysis, the proband is:

The ability to roll the tongue is caused by a dominant allele. A woman is a "roller," but one of her parents is not. The woman is expecting a child with a man who is a "nonroller." What is the probability that their first child will be a "roller"?

If the characteristic followed in the pedigree is X-linked recessive allele, what is III-1's genotype?

Two parents are phenotypically normal, but one of their four biological children has a typical autosomal recessive trait. The other three children are phenotypically normal. It is very likely that:

Which statement is INCORRECT concerning an X-linked recessive trait in humans?

If the pedigree below is for an autosomal recessive characteristic, which individuals are definitely heterozygous?

Most pedigrees showing the hypothetical human trait show the following characteristics: • Only males are affected. • Affected fathers always pass the trait to sons. What is the MOST likely mode of inheritance for this disorder?

Which of the following is NOT a characteristic of X-linked recessive traits in humans?

Which term refers to mating between closely related people?

Which of the following is NOT a typical characteristic of human traits that follow an autosomal recessive inheritance pattern?

The ability to roll the tongue is caused by a dominant allele. A woman is a "roller," but one of her parents is not. What is the woman's genotype?