Biotechnology and its Applications — Part 2: Gene therapy, diagnosis, transgenic animals and ethics: visual lesson, ISC Class 12 Biology

Lesson

Healing, testing and the questions it raises

Part 2 — correcting faulty genes, detecting disease early, using transgenic animals, and the ethics of it all.

In this lesson you will

Describe gene therapy for ADA deficiency (SCID)
Explain molecular diagnosis by PCR, ELISA and DNA or RNA probes
Give the uses of transgenic animals, and explain the role of GEAC, biopiracy and biopatents

Concept

Gene therapy for ADA deficiency

Gene therapy corrects a gene defect by delivering a normal gene into a person. The first clinical gene therapy (1990) treated a four-year-old girl with adenosine deaminase (ADA) deficiency, which causes severe combined immunodeficiency (SCID).

Worked example

Worked example 1: how many cells were corrected?

In a gene-therapy trial, 200 million lymphocytes were treated with the retroviral vector and 30 million took up the functional ADA gene. What percentage was corrected, and why must the treatment be repeated?

Corrected $= \dfrac{30}{200} \times 100 = 15$ percent.
Mature lymphocytes are not immortal, so the corrected cells die out and fresh infusions are needed.

Worked table: 15 percent of lymphocytes corrected
Cells	Millions
Treated	200
Took up ADA gene	30
Percent corrected	15

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