If a stretch of human double stranded DNA contains 47% G + C, then
a. it contains 47% A + T
b. there are more pyrimidines than purines
c. there are more purines than pyrimidines
d. it contains 53% A + T
e. there are no genes in this stretch of DNA
D
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A gram-positive Bacillus, which is c-hemolytic on 5% sheep blood agar, produces a wide zone of lecithinase on egg yolk agar, is nonmotile, and was isolated from the stool of a patient with abdominal pain and watery diarrhea. Because of the patient's existing immunocompromised state, the physician administered penicillin as the antibiotic therapy. The patient's condition did not improve after 7
days of treatment. Which one of the following statements explains the reason for the antibiotic failure? a. The course was too abbreviated and should be given for 14 days. b. The patient may be allergic to penicillin and its therapeutic effects. c. Penicillin is ineffective against gram-positive organisms. d. The organism produces c-lactamase, which renders the drug inactive.
Transcription factors control which of the following phases of pattern formation in the human embryo?
A. formation of body axes and segmentation B. segmentation and development of segment characteristics C. segmentation, development of segment characteristics, and cell differentiation D. formation of body axes, segmentation, development of segment characteristics, and cell differentiation E. cell differentiation
Studies of chromosomal and mitochondrial DNA suggest all of the following EXCEPT that every
locus exhibits some variability in its nucleotide sequence
a. among individuals from a single population. d. within species in a genus. b. between populations of the same species. e. within an individual. c. between related species.
The genetic information carried by DNA is in the ___ and their ___.
A) phosphates; phosphodiester bonds B) sugars; atoms C) base-pairing; hydrogen bonds D) bases; sequence