Case Study Questions for Class 12 Biology Chapter 8 Human Health and Diseases

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Case Study Questions for Class 12 Biology Chapter 8 Human Health and Diseases

Question 1:

In a study to test a new vaccine against a viral disease, mouse model testing is done. In this process, mice are vaccinated and their blood samples were tested. Mice developed mild disease symptom. After few days those mice were again infected with the virus. This time they do not show any disease symptoms. Their blood samples were tested. Two graphs show antibody concentration for the first and second infection in mice blood.

Based on the above information, answer the following questions.

(i) P and Q in the given graphs indicate
(a) IgM and IgG respectively
(b) IgG and IgM respectively
(c) IgG and IgE respectively
(d) IgM and IgA respectively.

(ii) Which form of pathogen is used in vaccination?

(a) Activated and strong pathogenic antigens
(b) Inactivated and weakened pathogenic antigens
(c) Hyperactive and strong pathogen
(d) Preformed antibodies

(iii) Which of the following is incorrect for P?
(a) It is the most abundant class of Ig.
(b) It is found in blood, lymph and intestine.
(c) It is unable to cross the placental barrier.
(d) It is a monomer.

(iv) How does vaccination work?
(a) The immune system produces antibodies which stay in the blood.
(b) Memory lymphocytes remain in the body to fight off any future infection with the same
(c) Antigenic proteins of pathogens generate primary immune response and the memory B and T cells.
(d) All of these.

(v) Read the given statements and select the correct option.
Statement A : Mice do not show any disease symptoms during second exposure to the pathogenic virus.
Statement B : The antibody production is accelerated and more intense during secondary immune response.
(a) Both statements A and B are true.
(b) Statement A is false but statement B is true.
(c) Statement A is true but statement B is false.
(d) Both statements A and B are false.

Answer Answer:
(i) (b) : Initial contact with an antigen causes primary immune response. In primary immune response, no antibodies are present initially. Then, a slow rise in the antibody titer occurs, first IgM and then IgG, followed by a gradual decline in antibody titer. In secondary immune response, the antibody formation is accelerated and more intense. This is also called booster response. It mainly consists of IgG antibodies.
(ii) (b) : Vaccine is a preparation or extract of an inactivated/ attenuated (weakened) pathogen of a disease which on inoculation into a healthy person provides immunity by inducing antibodies production.
(iii) (c) : IgG is the only class of antibody to cross the placenta from mother to fetus.
(iv) (d)
(v) (a)

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