Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
Four transgenic animals are described.
(1) A mouse that carries a human gene and develops a disease like cystic fibrosis.
(2) A cow whose milk holds a human protein.
(3) A mouse that is used to test a batch of the polio vaccine.
(4) An animal that carries genes that make it more sensitive to a toxic substance.
A transgenic animal has had its DNA manipulated to carry and express an extra, foreign gene. Over 95 per cent of existing transgenic animals are mice. They are made to study how genes work, as models of disease, to produce biological products, to test the safety of vaccines and to test the safety of chemicals. The first transgenic cow, Rosie, in 1997, made milk with human alpha-lactalbumin, 2.4 grams in every litre.
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) (1) Study of disease. (2) Biological products. (3) Vaccine safety. (4) Chemical safety testing.
Step 2. (b) Example (3). Transgenic mice may replace monkeys in the safety test of the polio vaccine.
Step 3. (c) Example (4). The more sensitive animal shows the effect of the chemical sooner.
Answer: (a) disease, products, vaccine safety, chemical safety; (b) 3; (c) 4.
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