Which of the following structural characteristics is not normally observed in a DNA duplex?
(a) purine–pyrimidine pairs
(b) external sugar–phosphate backbone
(c) uniform left-handed twist
(d) antiparallel strands
(c)
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Laboratory diagnosis of HIV infection is usually made by which of the following?
A) electron microscopy B) growth of HIV in cell culture C) growth of HIV in embryonated chicken eggs D) immunodiagnostic procedures for the detection of antigen and antibodies
How many planes divide the body of a biradially symmetric animal into two equal parts?
a. none b. 1 c. 2 d. 4 e. more than 4
When a plant is heterosporous, what does this mean?
a. It has both sporophyte and gametophyte generations. b. It has male and female gametes. c. It has two spore types. d. It has separate male and female plants.
The fungi that cause serious plant disease, such as Dutch elm disease and chestnut blight, belong to the phylum
A. Glomeromycota. B. Actinomycetes. C. Ascomycota. D. Basidiomycota. E. Zygomycota.