Biology

Human Genetics and Disorders

882 Questions

Human Genetics and Disorders covers the inheritance patterns, genetic mutations, and molecular basis of hereditary diseases. Topics include sex-linked traits, cancer genetics, and metabolic disorders. This section tests knowledge critical for biology exams and general science papers.

Genetic mutationsInherited disordersCancer geneticsGenetic testingMendelian inheritance

Human Genetics and Disorders Questions

Multiple choice

A man and a woman, who do not show any apparent signs of a certain inherited disease, have seven children (2 daughters and 5 sons). Three of the sons suffer from the given disease but none of the daughters is affected. Which of the following mode of inheritance do you suggest for this disease?

  1. Sex-limited recessive

  2. Autosomal dominant

  3. Sex-linked recessive

  4. Sex-linked dominant.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

 Sex-linked recessive traits typically occur only in males. Because the sex-linked trait is invariably X-linked, males transmit the trait only to their daughters, all of whom become carriers. Carrier (heterozygous) females can then transmit the trait to 50% of their male and female offspring. Affected males are hemizygous for the X-linked trait.

Multiple choice

Which of the following is not a hereditary disease?

  1. Haemophilia

  2. Cretinism

  3. Cystic fibrosis

  4. Thalassaemia
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 Cretinism is a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones (congenital hypothyroidism) usually due to maternal hypothyroidism.

Multiple choice

Haemophilia is more commonly seen in human males than in human females because

  1. this disease is due to a Y-linked recessive mutation.

  2. this disease is due to an X-linked recessive mutation.

  3. this disease is due to an X-linked dominant mutation.

  4. a greater proportion of girls die in infancy.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 Haemophilia is more commonly seen in human males than in human females because this disease is due to an X-linked recessive mutation.X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed in males (who are necessarily hemizygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation.

Multiple choice

A sequence-based molecular diagnostic test reveals that an affected child has a missense mutation in a gene known to be associated with a dominantly-inherited disorder. The child is the first member of the family to be affected, and the disorder is associated with complete penetrance. The mutation has never been seen before, either in affected individuals or in controls. Which of the following would be the most powerful evidence that the mutation is pathogenic?

  1. Test both parents to see if the mutation is found only in the child.

  2. Determine whether the mutation affects an amino acid that is conserved in evolution.

  3. Examine the structure of the protein to see if the mutation has a major effect on protein function.

  4. Review the literature to see if the mutation has been reported to be pathogenic.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The child is expected to have a new mutation given that the disorder displays complete penetrance and both parents are unaffected. Therefore, one would predict that the mutation would not be found in either parent (although germline mosaicism would be possible).

Multiple choice

Lactase deficiency is

  1. equally common throughout the world

  2. at its highest frequency in Europe

  3. at its minimum frequency in Asia

  4. none of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Lactase deficiency has a non-random distribution. Generally, it is the least common among Europeans. Asians and Native Americans have very high frequencies. In Africa, there are regions of extremely high frequency and others of low frequency.

Multiple choice

Sickle-cell trait was selected by nature in whole Central Africa because

  1. it provides prominent immunity to chronic anemia

  2. it provides little immunity against malaria

  3. it provides little immunity against thalassemia

  4. it provides little immunity against gout
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The microscopic organisms that cause malaria are parasites on normal red blood cells. Full-blown sicklers produce abnormal and deformed red cells. As a result, they are poor hosts for this disease and are immune. However, they are frequently anemic.

Multiple choice

The Rh mother-fetus incompatibility problems occur more severely in

  1. Europeans

  2. Africans

  3. Native Americans

  4. All are at equal risk.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Europeans have the highest frequency of Rh negative people (40%), which puts them at the highest risk for this problem. About 13% of newborn Europeans are at risk, but we can now prevent the life threatening complications in most cases.

Multiple choice

Which of the following is a glycogen storage disease?

  1. Von Gierke's disease

  2. Ehlers–Danlos syndrome

  3. Sickle cell anaemia

  4. Alzheimer's disease

  5. Klinefelter syndrome

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Glycogen storage disease type I or von Gierke's disease is the most common of the glycogen storage diseases. This genetic disease results from deficiency of the enzyme glucose-6-phosphatase.

Multiple choice

Mr. X is found to be homozygous for the e4 allele at ApoE. Which of the following statements regarding his risk of Alzheimer disease is true?

  1. He will almost certainly develop Alzheimer disease.

  2. He is protected from Alzheimer disease.

  3. He is at increased risk of Alzheimer disease.

  4. This result has no bearing on his risk of Alzheimer disease.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The e4 allele is associated with an increased relative risk of Alzheimer disease, but it is not diagnostic.

Multiple choice

A couple have a child with a trait believed to be determined by multifactorial inheritance. There is no known family history of the disorder. Which of the following statements is true regarding their recurrence risk?

  1. They are not at increased risk due to the absence of prior family history.

  2. They are only at increased risk if they are related to one another.

  3. They are only at increased risk if the next child is of the same sex as the previously affected child.

  4. They are at increased risk, which can be estimated from empirical data.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Empirical data is used in counseling for multifactorial inheritance.

Multiple choice

Which of the following is caused by the microdeletion of chromosome 7q11.2?

  1. Cowden syndrome

  2. Li-Fraumeni syndrome

  3. Williams syndrome

  4. Angelman syndrome
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

It is a chromosomal disorder and can be transmitted as dominant trait. It is caused by the microdeletion of chromosome 7q11.2 leading to deletion of elastin gene. It isusually not visible cytogenetically, but detectable by FISH or comparative genomic hybridization.

Multiple choice

The rocker bottom feet is a major symptom of

  1. trisomy 13

  2. trisomy 18

  3. trisomy 21

  4. trisomy 15
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Children with trisomy 13 are born with low birth weight and have multiple congenital anomalies. Most notable are facial anomalies, including hypotelorism, cleft lip and palate with rocker bottom feet.