All of the following events occur during prometaphase EXCEPT:a
the nuclear envelope breaks down.
b. the nucleoli disappear.
c. the mitotic spindle is completely assembled.
d. the spindle fibers "capture" chromosomes.
e. the duplicated chromosomes become visible with the light microscope
E
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During fertilization, the acrosome _____
A) prevents polyspermy by releasing enzymes that destroy surrounding sperm B) digests the coatings surrounding the plasma membrane of the egg C) nourishes sperm mitochondria, increasing sperm motility D) injects the sperm nucleus into the egg during fertilization
Which of the following statements is not a reason that conifers are absent from the tropics and are seemingly restricted to more temperate, cooler regions?
A. Conifers' single-celled tracheids cannot support large levels of transpiration, whereas those of angiosperms can. B. Conifer pollination was not as effective in the tropics as their populations became fragmented by angiosperm competition. C. In colder regions the dangers of cavitation due to freezing restrict angiosperm growth. D. In drier regions, the dangers of cavitation due to drought restrict conifer growth.
Gene therapy
a. has not yet been used successfully with mammals. b. is a surgical technique that replaces defective genes with normal genes. c. has been used successfully to treat victims of autosomal dominant disorders by replacing the dominant allele with a recessive allele. d. is a genetic engineering technique that replaces defective alleles with normal ones. e. is none of these.
Which structure is typical of the basidiomycetes?
A. basidium B. hyphae C. ascus D. zygosporangium