The leading preventable cause of birth defects is exposure of the fetus to:
A. X-rays.
B. cigarette smoke.
C. alcohol.
D. the herpes virus.
E. mercury.
C
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During a microarray analysis, cDNAs made from normal cells are stained with a green fluor and cDNAs from
abnormal cells are stained with a red fluor. Which of the following statements is true about the results of this experiment?
a. Red spots indicate genes that are under expressed in abnormal cells. b. Red spots indicate genes that are not expressed in abnormal cells. c. Red spots indicate genes that are overexpressed in abnormal cells. d. Red spots indicate genes that are overexpressed in normal cells. e. Red spots indicate pseudogenes.
The developmental stage represented in Figure 51-2 is:
a. a morula. b. an early blastula. c. a late blastula. d. an early gastrula. e. a middle gastrula
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.
A(n) (nonpolar/polar/ionic/hydrogen) bond is one in which electrons are shared equally between atoms.
Fill in the blank(s) with the appropriate word(s).