Question

13) The enzymes that can selectively cut DNA at specific locations during various types of gonetic recombination are called. a. R factors. b. bacterial transposons, c.clone. d. restriction endonucleases 14) Which of the following items is not a partof a compound light microscope? 15).Which of the following infectious agents causes typhus? 16)、The mosquito Anopheles is a a. cathode, b. objective lens c eyepiece d. dise aperture diaphragn a. togavirus b. lavivirus c . Yersinia pestis d. Rickettsia prowazekii a mechanical vector b. biological vector c transcendent vector d. none of the above 17) Serological identification of bacteria is based upon a. Selective binding of bacterial antigens to specific antibodies b. Selective binding of bacterial antibodies to specific antibsotics. c. Selective binding of bacterial antigens to specific immunogens. d. Selective binding of bacterial antigens to the cells of laboratory test animals. 13) The form of interdependency between organisms in which both participants beneft from the association is called д. ecology. b.commensalism. c.parasitism. . mutualism. 19) A long term relationship between a host and a pathogen is called a. parasitism. b. inflammation. c.chronic infection. d.acute infection. 20) A pathogenic microorganism may damage a host by a. Destruction of tissue near the site of entry b. Dissemination throughout the body to cause widespread damage. c. Secretion of toxins that disseminate throughout the body causing widespread damage. d. All of these. 21) Type of phagocytic cell present in tissues a. neutrophils b. macrophage c. eosinophils d. basophils 22) Type of lymphocyte programmed to destroy corrupt "self cells a. Helper T cell b. Cytotoxic T cell c. dendritic cell d. all of the above 23) Account for most of the circulating leukocytes b. macrophage a. neutrophils c. eosinophils d. basophils 24) Release histamine and other inflammatory inducing chemicals from the granules a. neutrophils b. macrophage c. eosinophils d. basophils 25) These circulating cells differentiate into either macrophages or dendritic cells when they mig c. lymphocytes d. basophils ssue b. monocytes neutrophils

Answer 1

Question number	Answer	Detailed Explanation
13	d	Restriction endonucleases are the enzymes that cut DNA at specific nucleotide sequences known as restriction sites.These restriction sites are usually 4 to 8 bases long.These restriction endonucleases cut DNA and produces two types of ends: Sticky ends Example: EcoRI digestion produces sticky ends Blunt ends Example: SmaI digestion produces blunt ends.
14	a	Compound light microscope is an optical instrument for forming magnified images of small objects, consisting of an objective lens with a very short focal length and an eye piece with a longer focal length and disc aperture diaphragm
15	d	Rickettsia prowazekki is pleomorphic, obligate intracellular gram-negative coccobacillus bacteria is the causative agent of Epidemic Typhus. This is transmitted in the feces of lice. This R.prowazekki causes endothelial cell injury which leads to increased permaebility of vascular endothelium and vasodilation and in severe cases leads to multi organ system failure
16	b	Biological vector can carry pathogens that can multiply within their bodies and be delivered to new hosts by biting Example: Female anopheles are vectors that transmits Plasmodium vivax, a malarial parasite to human body
17	a	Serological testing is performed to detect and measure the levels of antibodies as a result of exposure to particular bacteria.When individual exposed to bacteria (antigens), their body's immune system produces specific antibodies against the organism. Antibody titer helped to determine whether the infection occured recently or years ago.
18	d	Mutualism is when two organisms both help one another in a form of interdependence. Example: ants and acacia tree form a symbiotic relationship of mutualism. The ants benefit by living in the acacia tree, and the tree benefits when the ants consume the insects that eat the leaves of the tree.
19	a	Parasitism is a long-term relationship between two species where one species (the parasite) benifits at the expense of the other, the host. Example: Fleas or ticks that live on dogs and cats are parasites. They are used to suck the blood of the host animal.
20	d	The ability of the pathogen to cause damage in the host is by direct damage or by secretion of toxins. Direct damage is the generalized mechanism utilized by the pathogenic organisms to ensure infection and destruction to the host cell. Pathogenic organisms produce poisonous substances called toxins that leads to the host cell damage Example: Staphylococcus aureus produces enterotoxin B which is associated with intestinal illness.
21	b	Macriophages are phagocytic cells located in the tissues. The monocytes formed in the bone marrow is transported by the blood and migrated to the tissue where it is get transformed to macrophages. Example: Kupffer cells in the liver Alveolar macrophages in lungs
22	b	Cytotoxic T cells is a T-lymphocyte that kills damaged cells
23	a	Neutrophils are the most abundant white blood cells, constituting 60 to 70% of circulating leukocytes
24	d	Basophils are type of white blood cells that represent about 0.5 to 1% of circulating leukocytes. these cells consists of granules that release histamine and other inflammatory agents.
25	b	The monocytes formed in the bone marrow are transported by blood and migrated to tissues where it get transformed to macrophages or dendritic cells. Example: Kupffer cells are the macrophages that reside in the liver.