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

Which among the following is caused by mutation in OPN1LW and OPN1MW genes?

  1. Red-Green colour blindness

  2. Hereditary deafness

  3. Tyrosinemia

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

It is a X-linked recessive disease. It is caused by mutation in OPN1LW and OPN1MW, encoding red and green sensitive opsins. These genes are clustered on the X chromosome, with one red pigment gene followed by 1-6 green pigment genes. Unequal crossover events between these genes lead to creation of non-expressed hybrid genes and deletions.

Multiple choice

Microsatellite instability is associated with

  1. hereditary nonpolyposis colon cancer

  2. familial adenomatous polyposis

  3. hereditary breast cancer

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

Microsatellite instability results from aberrant mismatch repair and is characteristic of HNPCC.

Multiple choice

A 5 year old boy with developmental delay is seen for evaluation. He has microcephaly, and his parents note that his birth weight was low. There is no known family history of similar problems. As routine karyotype is normal. His parents ask if there are additional cytogenetic tests that can be offered. What would be the suggestion to them?

  1. The chromosome study should be repeated in another laboratory.

  2. A normal karyotype rules out all detectable chromosomal abnormalities.

  3. The boy should have FISH analysis for all known microdeletions.

  4. Analysis for subtelomere deletion may detect an abnormality missed by convential chromosomal analysis.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Subtelomere analysis does offer a possibility to detect an abnormality that was not seen by conventional cytogenetic analysis.

Multiple choice

Which of the following types of mutations is not be expected to be detected in a molecular diagnostic test that is based on sequencing each exon of a gene in genomic DNA from a male suspected of having a X-linked disorder?

  1. Missense mutation

  2. Nonsense mutation

  3. Deletion of an exon

  4. Inversion of part of the gene
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

An inversion of part of the gene would not cause the exons to be absent or missing, and the sequencing reaction would not reveal that the exons are no longer arranged in the proper order on genomic DNA.

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 or not.

  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, it would predict that the mutation would not be found in either parent (although germline mosaicism would be possible).

Multiple choice

Which of the following is/are the outcome(s) of pleiotropy?

a. Increased resistance to falciparum malaria in sickle cell anemia b. Abnormal mucus production in cystic fibrosis c. Appearance of delicious apple and navel oranges

  1. only a

  2. only b

  3. a and b

  4. only c
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In both cases, i.e. falciparum resistance and abnormal mucus production, mutation in one gene results in more than one phenotypic trait. Thus, both are examples of pleiotropy.

Multiple choice

Which of the following are XY-linked hereditary disorders?

  1. Colour vision deficiency
  2. Ambras syndrome
  3. Haemophilia
  4. Retinitis pigmentosa
  5. Complete colour blindness

  1. 1 and 2

  2. 2 and 3

  3. 1 and 4

  4. 3 and 4

  5. 4 and 5
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This option is correct because retinitis pigmentosa is an XY-linked hereditary, degenerative eye disease that causes severe vision impairment and often blindness. Complete colour blindness is a severe vision imparement, leaving a person completely unable to distinguish any colour. It is an XY-linked hereditary disease.