Question 1

Which of the following best describes autosomal recessive inheritance?

Accepted Answer

Two copies of the mutant allele are required for the phenotype to be expressed.

Question 2

A couple, both carriers for cystic fibrosis ($$Cc$$), are planning to have a child. What is the probability that their child will be affected by cystic fibrosis?

Accepted Answer

$$\frac{1}{4}$$

Question 3

Which of the following diseases is NOT typically inherited in an autosomal recessive manner?

Accepted Answer

Huntington's disease

Question 4

In a pedigree analysis, which pattern is most indicative of autosomal recessive inheritance?

Accepted Answer

Trait skips generations and appears in siblings but not in parents.

Question 5

Consanguinity increases the risk of autosomal recessive disorders because:

Accepted Answer

Parents are more likely to share common ancestors and identical recessive alleles.

Question 6

A child is born to two unaffected parents, both of whom are carriers for an autosomal recessive disorder. What is the probability that the child will be a carrier?

Accepted Answer

$$\frac{1}{2}$$

Question 7

Which of the following statements about Tay-Sachs disease is correct?

Accepted Answer

It is caused by a mutation in the gene encoding hexosaminidase A.

Question 8

A pedigree shows two unaffected parents with an affected child. What is the most likely mode of inheritance for the disorder?

Accepted Answer

Autosomal recessive

Question 9

Which of the following is a common symptom of Tay-Sachs disease?

Accepted Answer

Progressive neurological deterioration

Question 10

Hemochromatosis type 1 is most commonly caused by mutations in which gene?

Accepted Answer

HFE

Question 11

If both parents are affected by an autosomal recessive disorder, what is the expected genotype of their offspring?

Accepted Answer

All offspring will be homozygous affected.

Question 12

Which equation correctly represents the probability ($$P) of $$two carrier parents ($$Aa) $$having an affected child for an autosomal recessive disorder?

Accepted Answer

$$P = \frac{1}{4}$$

Question 13

Which population is at increased risk for autosomal recessive disorders due to genetic isolation?

Accepted Answer

Populations sharing religion, geography, or language

Question 14

What is the function of the hexosaminidase A enzyme, which is deficient in Tay-Sachs disease?

Accepted Answer

Breaks down GM$$_2$$ gangliosides in neurons

Question 15

A pedigree shows that an autosomal recessive trait appears only in siblings, not in parents or offspring. What does this suggest about the parents?

Accepted Answer

Both parents are carriers.

Question 16

Which of the following is a recommended treatment for hereditary hemochromatosis type 1?

Accepted Answer

Phlebotomy to remove excess iron from the body

Question 17

Which of the following symptoms is NOT associated with Tay-Sachs disease?

Accepted Answer

Excess iron deposition in the liver

Question 18

What is the most common mutation in the Hex-A gene causing Tay-Sachs disease?

Accepted Answer

A 4-base insertion (1278insTATC)

Question 19

Which of the following statements about the treatment of hereditary hemochromatosis type 1 is correct?

Accepted Answer

Serum ferritin levels are monitored to guide phlebotomy.

Question 20

If a population has a high rate of consanguinity, what is the expected effect on the frequency of autosomal recessive disorders?

Accepted Answer

Frequency will increase due to higher rates of homozygosity for recessive alleles.

Autosomal Recessive Inheritance: Principles, Pedigrees, and Disease Examples

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