NEET Practice Questions (MCQs) with Answers & Solutions

158.(d) : Influenza A virus subtype H5N1, also known as A (H5N1) or H5N1, is a subtype of the influenza A virus that can cause illness in humans and many other animal species. A bird-adapted strain of H5N1, called HPAI A(H5N1) for "highly pathogenic avian influenza virus of type A of subtype H5N1", is the causative agent of H5N1 flu, commonly known as "avian influenza" or "bird flu". It is endemic in many bird populations, especially in Southeast Asia. One strain of HPAI A(H5N1) is spreading globally after first appearing in Asia. It is epizootic (an epidemic in nonhumans) and panzootic (affecting animals of many species, specially over a wide area), killing tens of millions of birds and spurring the culling of hundreds of millions of others to stem its spread. HPA1A(H5N1) is an avian disease. H5N1 is mainly spread by domestic poultry, both through the movements of infected birds and poultry product and through the use of infected poultry manure as fertiliser or feed. Humans with H5N1 have typically caught it from chickens, which were in turn infected by other poultry or waterfowl. Migrating waterfowl (wild ducks, geese and swans) carry H5N1, often without themselves becoming sick. Many species of birds and mammals can be infected with HPAI A (H5N1), but the role of animals other than poultry and waterfowl as disease-spreading hosts is unknown.

(a) : The degree of pathogenicity of a microorganism is called virulence. This is indicated by case fatality rates and/or its ability to invade the tissues of the host; the competence of any infectious agent to produce pathological effects.

(a) : Hepatitis A caused by picornavirus a positive stranded RNA virus Hepatitis B - caused by partially double stranded, and partially single stranded DNA virus called Hydra virus.

(b): Cocaine is a natural alkaloid obtained from leaves of Erthyroxylon coca. Its chemical formula is C₁₇H₂₁ NO₄. It is a powerful CNS stimulant. It causes lack of sleep and loss of appetite.

Escherichia coli is the non-pathogenic bacteria of colon. One of the characteristics of Escherichia coli is the production of bacteriocins (colerains), a specific type of metabolite which is not only lethal to the organism of the same species but also to related organisms. Balantidium coli results in inflammation of alimentary tract. Entamoeba coli causes amoebic dysentery. Enterobius vermicularis infection is known as oxyuriasis or enterobiosis.

(d)

(a) In Entamoeba histolytica, the precystic or minute forms encyst only in the lumen of the intestine. In precystic stage, the chromatid bodies are found which disappear as the cysts mature.

(d): Wuchereria bancrofti is a dreaded human parasite. It is digenetic parasite completing its life cycle in two hosts, the final host is man harbouring the adult worm. The adult worms live coiled up in the gland and lymph vessels of man.  

(d) : Sonography is a technique to visualise the structures beneath the skin. A transducer is used to recieve soundwave and signals to the skin. The transducer contains the crystals of lead zirconate that convert electric current into sound waves. Transducer also act as a reciever and converts the echoes into electrical signals which are processed and displayed on the screen of a monitor to show 2-D image.

Electron beam therapy or radiation therapy involves the use of radioactive waves to treat certain types of cancer. The therapy can be given with external beams of radiation. Electron beams are of low energy. They are often used in skin conditions and cancers. The procedure to deliver external beam radiation is somewhat similar to giving an X-ray. The person is put into position, and the machine delivers the radiation to the desired area. This beam therapy involves iodine, cobalt, protons and electrons. This therapy is used in cancer of cervix, cancer of larynx, germ cell cancer, hodgkin's lymphoma, prostate cancer, breast cancer, lung cancer etc.