Methicillin-resistant Staphylococcus aureus (MRSA) can be a serious threat to human health. There is evidence that S. aureus infections are common in hospitals and that MRSA have become resistant to other antibiotics besides methicillin. This suggests that the rapid evolution of resistance in the bacteria poses a serious public-health challenge. Which of the following best explains the ability of MRSA to evade existing drug therapies?
(A) MRSA have very long generation times and very large population sizes.
(B) MRSA develop new alleles by intentionally introducing specific mutations that will give them a selective advantage over other bacteria.
(C) MRSA metabolize many drugs in their lysosomes and therefore evolve resistance at a high rate.
(D) MRSA exchange genetic material with other antibiotic-resistant bacteria, which can spread resistance in the S. aureus population.
Answer: (D) MRSA exchange genetic material with other antibiotic-resistant bacteria, which can spread resistance in the S. aureus population.
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The single-factor crosses performed by Mendel support the observation that
A. the two alleles for a given gene are distributed randomly among an individual's gametes. B. the two alleles for a given gene are found within the same gamete. C. if the recessive alleles for two different genes are on the same chromosome, they will never be found within the same gamete. D. only the dominant alleles for a given trait are found in an organism's gametes. E. if the dominant alleles for two different genes are on different chromosomes, they will never be found within the same gamete.
Irregular dental hygiene and a high sugar diet may led to tooth decay. Why?
A. Bacteria consume calcium. B. Lactic acid fermentation is used to generate ATP under anaerobic conditions. C. Plaque degrades the tooth's protective mucosal layers. D. Glucose forms a weak acid when dissolved in saliva. E. High concentrations of sugar soften the tooth enamel. Clarify Question · What is the key concept addressed by the question? · What type of thinking is required? Gather Content · What do you already know about teeth? How does it relate to the question? · What other information is related to the question? Which information is most useful? Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer? Reflect on Process · Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
Asexual reproduction produces genetically identical individuals because
a. chromosomes do not have to replicate during asexual reproduction. b. it involves chromosome replication without cytokinesis. c. no meiosis or fertilization take place. d. cell division occurs only in meiosis. e. the mitotic spindle prevents nondisjunction.
Master genes that affect development tend to be highly ____; therefore, similarities in patterns of embryonic development reflect shared ancestry that can be evolutionarily ancient.
a. homologous
b. degraded
c. conserved
d. mutated
e. related