Directions : In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as :
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) If assertion is true but reason is false.
(d) If assertion is false but reason is true.
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Assertion : Streptococcus pneumoniae and Haemophilus influenzae are responsible for causing infectious disease in human beings.
Reason: A healthy person acquires the infection by inhaling the droplets/aerosols released by an infected person.
(b)
Assertion : In malaria, a person experiences chills and high fever recurring every three to four days.
Reason : This is caused by the release of haemozoin with rupture of liver cells.
(c) : Malignant malaria caused by Plasmodium falciparum is the most serious one and can even be fatal. The parasites initially multiply within the liver cells and then attack the red blood cells (RBCs) resulting in their rupture. The rupture of RBCs is associated with release of a toxic substance, haemozoin, which is responsible for the chill and high fever recurring every three to four days.
Assertion : Inspite of exposure to large number of infectious agents humans are resistant to diseases.
Reason : Humans are able to defend against most of the foreign agents due to the ability to fight diseasecausing organisms.
(a)
Assertion : Mucous membrane immobilises the microorganisms in the body.
Reason : Microorganisms and dust particles entering the respiratory tract are trapped in the mucus.
(b) : Innate immunity is non-specific type of defence, that is accomplished by providing different types of barriers to the entry of the foreign agents into our body. Mucus coating of the epithelium lining in the respiratory, gastrointestinal and urogenital tracts traps microbes and prevents their entry in our body.
Assertion : Virus-infected cells secrete proteins known as interferons.
Reason : Interferons protect the non-infected cells from bacterial infection.
(c) : Virus-infected cells secrete proteins called interferons which protect non-infected cells from further viral infection.
Assertion : Subsequent encounter with the same pathogen elicits a highly intensified response.
Reason : This is based on the fact that our body appears to have memory of the first encounter.
(a)
Assertion : All immunoglobulin molecules have a basic structure composed of four polypeptide chains.
Reason : The polypeptide chains consists two identical heavy and light chain connected by disulphide bonds.
(b)
Assertion : \(\lg G\) is the most abundant class of lgs in the body.
Reason : \(\lg G\) is mainly found in sweat, tears, saliva, mucus, colostrum and gastrointestinal secretions.
(c) : IgG is the most abundant class of lgs in the body constituting approximately \(80 \%\) of the total Igs. It is found in the blood, lymph and intestine. \(\lg A\) is mainly found in sweat, tears, saliva, mucus, colostrum (first milk secreted by a mother) and gastrointestinal secretions.
Assertion : Cornea is considered as an immunologically privileged site.
Reason : A transplanted cornea is rarely rejected.
(a) : Some transplanted tissues do not stimulate an immune response. For example, a transplanted cornea is rarely rejected because lymphocytes do not circulate into the anterior chamber of the eye, thats why this site is considered as immunologically privileged site.
Assertion: Artificially acquired passive immunity results when antibodies or lymphocytes produced outside the host are introduced into a host.
Reason : A bone marrow transplant given to a patient with genetic immunodeficiency is an example of artificially acquired active immunity.
(b)
Assertion: Immunisation is achieved by the successful delivery of vaccines.
Reason : Vaccine is a preparation of one or more microbial agents, used to induce active immunity.
(a)
Assertion : Mucosa-associated lymphoid tissues are specialised immune barrier located on skin.
Reason : MALT constitutes about 50 percent of the lymphoid tissue in human body.
(d) : MALT are aggregation of lymphoid tissues found in the mucosa of major tracts like respiratory, alimentary canal and urogenital tract.
Assertion : Antiretroviral drugs are completely effective in treatment against AIDS.
Reason : AIDS virus is a retrovirus with ssRNA as genetic material.
(d) : Treatment of AIDS with anti-retroviral drugs is only partially effective. They can only prolong the life of the patient but cannot prevent death. AIDS virus is a retrovirus with ssRNA as a genetic material.
Assertion : Benign tumors are called neoplastic cells.
Reason : Malignant tumor spreads to other organs of the body.
(d)
Assertion: Proto-oncogenes are cellular genes required for normal growth.
Reason : Under normal conditions they could lead to the oncogenic transformation of the cell.
(c) : Proto-oncogenes are cellular genes required for normal growth. If they are muted or over expressed, they may become oncogenes that contribute to the malignant transformation of the cell.
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