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Living Environment Regents August 2010 Question 05 PDF Print E-mail
Friday, 27 May 2011 12:11
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Correct answer: (3) weakened viruses associated with the infection

Vaccines are harmless variants or derivatives of pathogenic microbes that stimulate the immune system to mount defenses against the actual pathogen. The term vaccine came from the word "vacca" which means cow in Latin. Edward Jenner, an English physician, formulated the first vaccine against smallpox virus in 1796. He learned from his patients in farm country that milkmaids who had slight cowpox (a milder disease that usually infect cows) were resistant to subsequent smallpox infections. He did his experiment by scratching a boy with a needle that contains a fluid from a sore of a milkmaid who had cowpox. The boy was later exposed to smallpox and he resisted the disease.

Incorrect answers:

(1) live bacteria that ingest viruses

Vaccines may contain weaker versions of pathogenic bacteria, but these will not ingest viruses. The bacteria will turn on the defense system of the body so that when the stronger bacteria invade the system, it has already formed the resistance against them.

(2) white blood cells from an infected individual

White blood cells are naturally occurring components of the blood produced by the hematopoietic stem cell that are involved in the defense against pathogens.

(4) a variety of microbes that will attack the virus

Vaccines cannot contain different types of microbes because these might cause various diseases to the individual.
 

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