Suppose that a DNA change results in the substitution of one codon for another, but the codon specifies the same amino acid as it did originally. What type of mutation has occurred?
a. a chromosomal mutation
b. a frameshift mutation
c. a silent mutation
d. a missense mutation
Ans: c. a silent mutation
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Some archaeons are symbionts in animal digestive tracts.
Answer the following statement true (T) or false (F)
The process of carbon dioxide fixation refers to
A. reaction of carbon dioxide with water to form carbonic acid. B. release of carbon dioxide during catabolic reactions. C. reduction of carbon dioxide and incorporation into organic molecules that are assimilated. D. release of carbon dioxide during anabolic reactions.
Match the following items with the correct phrases.
_______1. Semisynthetic penicillins that are known as penicillinase-resistant penicillins. _______2. Examples of antibiotics that inhibit cell wall synthesis. _______3. Semisynthetic penicillins that are not resistant to penicillinase. _______4. Examples of antibiotics that inhibit protein synthesis. _______5. Examples of antibiotics produced by molds. a. penicillin, bacitracin, cephalosporins, vancomycin b. ampicillin and carbenicillin c. methicillin, oxacillin, cloxacillin, nafcillin d. tetracycline, chloramphenicol, erythromycin, streptomycin e. penicillin and cephalosporins, but not bacitracin and vancomycin
How is the central portion of a T cell receptor complex functionally analogous to the center of the B cell receptor complex?
A. It has two pieces (chains), just like a B-cell receptor. B. Both receptors bind epitopes (small amino acid sections of antigen molecules). C. Both bind structures directly on the surface of microbes. D. Both can be secreted from lymphocytes to bind to pathogens under certain situations.