Which of the following statements describes the evolution by natural selection of Mycobacterium tuberculosis bacteria in their new environment?
A. The drug-resistance trait is an adaptation to the environment in which human hosts are medicated with the antibiotic rifampin.
B. The drug-resistance trait is an adaptation to the environment in which human hosts travel worldwide and are exposed to new strains of bacteria.
C. The drug-susceptiblity trait is an adaptation to the environment of antibacterial soaps.
D. The drug-susceptiblity trait is an adaptation to the environment in which human hosts are medicated with the antibiotic rifampin.
Answer: A. The drug-resistance trait is an adaptation to the environment in which human hosts are medicated with the antibiotic rifampin.
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Which of the following is not part of the mismatch repair (MMR) mechanism?
A. MutS and MutL form a complex at the site of the mismatch and while scanning in both directions along the DNA form a loop. B. Mismatched bases are recognized by MutS. C. When the MutS/MutL complex finds a GATC site, MutH binds to the complex and cleaves the methylated strand. D. Helicase and exonuclease activities unwind and degrade the strand containing the mismatched base. E. Pol III fills the gap and ligase seals the DNA strand.
In mismatch repair on newly replicated DNA, enzymes distinguish between old and newly replicated DNA strands based on the fact that newly replicated DNA strands are ________-methylated relative to older DNA.
Fill in the blank(s) with the appropriate word(s).
A reaction with a negative value of ?G is referred to as an __________ reaction
a. endergonic b. entropy c. exergonic d. enthalpy e. activation
What percentage of the earth's topsoil is lost to erosion each year?
A) 0.1 % B) 1% C) 10% D) 50% E) 100%