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Human Health and Disease — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYHuman Health and Disease1 Mark
Question
For question, two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
Assertion : SCID is the first genetic disorder to be combated with gene therapy.
Reason : SCID is a type of allergy.
✓

Answer

  1. Assertion is true, but reason is false.

Explanation:

Severe combined immunodeficiency (SCID) represents a group of rare, sometimes fatal, congenital disorders characterized by little or no immune response. The defining feature of SCID, commonly known as “bubble boy” disease, is a defect in the specialized white blood cells (B-and T-Iymphocytes) that defend us from infection by viruses, bacteria, and fungi. SCID is caused by a defect in the gene that codes for the enzyme adenosine deaminase on chromosome number 20. Lack of the enzyme adenosine deaminase (ADA), means that the substrates for this enzyme accumulate in the cells. Immature lymphoid cells of the immune system are particularly sensitive to the toxic effects of these unused substrates, so fail to.reach maturity. As a result, the immune system of the afflicted individual is severely compromised or completely lacking. Lack of this enzyme makes the body defenseless against infections. SCID is the first genetic disorder to be combated with gene therapy.

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