Genetics Quiz #6

The pedigree below shows the segregation of an autosomal recessive trait in humans. Unless there is evidence to the contrary, assume that individuals who marry into the family do not carry the recessive allele. If IV-1 and IV-2 marry, what is the probability that their first child will have this trait?

1/24

The pedigree below shows the segregation of an autosomal recessive trait. What is the probability that the child of III-1 and III-2 will be affected? Assume that individuals from outside the families are homozygous normal.

1/36

The pedigree below shows the sex-linked recessive inheritance of Nance-Horan syndrome, a rare Mendelian disorder in which affected persons have cataracts and abnormally shaped teeth. What is the probability that the first child of IV-6 and V-3 would have Nance-Horan syndrome?

1/8

Which term refers to mating between closely related people?

consanguinity

June has two brothers with Becker muscular dystrophy (BMD), an X-linked recessive condition that allows affected males to survive into adulthood. Her parents are phenotypically normal. She marries Sheldon who also has BMD. June and Sheldon have a daughter. What is the probability that this daughter will have BMD?

1/4

The pedigree below shows the segregation of an autosomal recessive trait. If III-3 and III-4 marry and have a child, what is the probability that this child will show the trait?

1/6

The pedigree below shows the segregation of an autosomal dominant trait. If IV-1 marries IV-5, what is the probability that their first child will be affected? Assume that the homozygous mutant genotype is viable and has the same phenotype as the heterozygote.

3/4

Fetal cell sorting is a(n):

procedure for detecting and separating fetal cells from maternal blood cells.

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

All of the above are characteristic of autosomal recessive inheritance.

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

All the sons of an affected father will be affected with the trait.

This form of prenatal testing is most commonly performed between the 15th week and 18th week of pregnancy.

amniocentesis

Assume that the concordance values for a particular disease are 63% for monozygotic twins and 36% for dizygotic twins. Which of the following are TRUE?

Environmental factors are important in susceptibility to this disease, and genetic factors are important in susceptibility to this disease.

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

An affected woman almost always has an affected mother.

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

No, the offspring of I-1 and I-2 contradict an autosomal dominant inheritance.

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

hemizygous for a dominant allele

If the phenotype followed in Pedigree 3 is X-linked recessive, then what is the genotype of II-2? Assume no new mutations and complete penetrance.

heterozygous

The pedigree below shows a rare autosomal recessive trait segregating. What is the probability of the first child of a marriage between III-3 and III-7 being affected?

1/12

A trait is caused by a rare recessive autosomal allele with full penetrance. Practically all individuals with the trait result from matings between normal individuals. What would be the expected concordance values for monozygotic and dizygotic twins?

100% for monozygotic twins and 25% for dizygotic twins

A trait is caused by a rare dominant autosomal allele with full penetrance. Practically all individuals with the trait are heterozygous and result from matings between affected and normal individuals. What would be the expected concordance values for monozygotic and dizygotic twins?

100% for monozygotic twins and 50% for dizygotic twins

Which of the following is NOT normally used to study the inheritance of human traits or disorders?

All of these are used in the study of human traits or disorders.

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

Affected daughters always have an affected mother.

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

I-1, I-2, II-4, II-5, III-1

Which of the following is NOT correctly identified as an advantage is using amniocentesis?

It can normally be done as early as the sixth week of pregnancy.

Which of the following statements is NOT true concerning newborn screening?

It is particularly important to test for serious conditions where there is no treatment available.

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?

Y-linked

If monozygotic and dizygotic twins have the same concordance value for a trait, which of the following is TRUE?

The trait is entirely due to environmental factors.

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?

X-linked dominant

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?

X-linked recessive

Assuming that it is not a Y-linked trait, suggest the MOST likely mode of inheritance for the rare trait shown in the pedigree below

autosomal dominant

What is the MOST likely mode of inheritance in the pedigree below?

autosomal dominant

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?

autosomal recessive

What is the MOST likely mode of inheritance for the trait segregating in the pedigree below?

autosomal recessive

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

autosomal recessive only

This form of prenatal testing is most commonly performed between the 10th week and 12th week of pregnancy and involves the insertion of a soft plastic into the vagina to obtain cells.

chorionic villus sampling

Heterozygous genetic screening is used mainly to:

detect adult members of a particular population who may be heterozygous carriers for recessive disorders.

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?

heterozygous

In pedigree analysis, consanguinity refers to:

mating between two closely related parents

Heterozygote screening normally involves:

testing adult members of a particular population to identify heterozygous carriers for a recessive disorder.

In pedigree analysis, the proband is:

the individual having the trait or disorder from whom the pedigree is initiated.

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:

the parents are both heterozygous for the trait