Most genome exists in the cytoplasm some are

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Most genome exists in the cytoplasm. Some are nonchromosomal and appear as plasmids in the cytoplasm or in organelles such as mitochondria and chloroplasts. 20. Differentiate between genotype and phenotype. Genotype is the sum of all types of genes that constitute the genetic makeup. Phenotype is the expression of the genotype that creates structures or functions. 21. List some of the characteristics of the DNA molecule. DNA is composed of nucleic acids (phosphate backbone, deoxyribose sugar, and nitrogenous bases). The nitrogenous bases are either purines (adenine and guanine) or pyrimidines (thymine and cytosine) that form specific bonds. DNA runs in an antiparallel arrangement and forms a double helix. 22. What are Okazaki fragments, the replication fork, the leading strand and the lagging strand? Okazaki fragments are short segments of DNA on the lagging strand that must be bound together. The replication fork is the place in the helix where the strands are unwound and where synthesis is taking place. The leading strand is synthesized in the 5’ to 3’ direction, following the path of helicase. The lagging strand is synthesized in short Okazaki fragments and is later sealed in the 3’ to 5’ direction. 23. Differentiate between the functions of DNA polymerase I and III. DNA polymerase III adds bases to the new DNA strand and can also proofread for mistakes. DNA polymerase I removes the RNA primer and
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closes gaps and is capable of repairing mismatches. 24. List some important characteristics of antimicrobial drugs. The ideal antimicrobial drug is microbicidal rather than microbistatic. It is soluble. It attacks only the microbe and not the host. It complements the hosts defenses. It does not cause reactions like allergies. 25. What are the mechanisms of action for polymyxins and penicillins what cellular structures do they target? Polymyxins and penicillins inhibit the cell membrane and cell wall respectively. Polymyxin distorts the cell surface and causes leakage of protein and nitrogen bases, particularly in G- bacteria. Penicillin blocks cell wall synthesis and repair in G+ cocci and in some G- bacteria. They are both narrow spectrum. 26. List the different cellular mechanisms of Bacterial resistance to antimicrobial agents. Bacteria can synthesize new enzymes that inactivate the drug. The permeability or uptake of the drug is decreased. The drug is immediately eliminated by efflux pumps. Binding sites are decreased in number or affinity. Metabolic pathway is shut down or alternative is used. 27. Give an example of how antimicrobial drug resistance might be deterred (prevented or overcome).
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  • Fall '12
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