OBJECTIVE LIFE SCIENCE
EVOLUTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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A mule, despite being the product of two different species (a horse and a donkey).
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An alligator. Alligators still survive, despite being dated by fossils to the time of dinosaurs.
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A species of African cichlid fish, which is thought to have rapidly evolved, along with 500 other similar species.
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A staph bacteria in a hospital that is not killed by penicillin or several other antibiotics.
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Detailed explanation-1: -Staphylococcus aureus is naturally susceptible to virtually every antibiotic that has ever been developed. Resistance is often acquired by horizontal transfer to genes from outside sources, although chromosomal mutation and antibiotic selection are also important. This exquisite susceptibility of S.
Detailed explanation-2: -Unfortunately, some strains of Staph have become resistant to methicillin and other similar antibiotics. These strains are known as MRSA, which cannot be cured with traditional penicillin-related drugs. Instead, MRSA must be treated with alternate antibiotics.
Detailed explanation-3: -Vancomycin therapy carries specific risks, particularly renal dysfunction, but despite its foibles, vancomycin remains the standard of care for the treatment of resistant staphylococcal infections.
Detailed explanation-4: -Mechanisms of resistance. Staphylococcal resistance to penicillin is mediated by blaZ, the gene that encodes -lactamase (Figure 2a). This predominantly extracellular enzyme, synthesized when staphylococci are exposed to -lactam antibiotics, hydrolyzes the -lactam ring, rendering the -lactam inactive.