Discuss the ways in which light rays can be manipulated to increase resolution and/or contrast
What will be an ideal response?
Light rays can be manipulated to increase the resolution and contrast of a specimen in a variety of ways. In bright-field microscopes, immersion oil is used to capture light rays that would otherwise be refracted and lost; the result is an increase in the resolution of the image. Dark-field microscopes purposely scatter light rays in such a way as to improve the contrast of the specimen. Phase-contrast microscopes alter the wavelengths of light rays by splitting them into different paths then rejoining them, thereby increasing contrast. Finally, fluorescent microscopes use UV light, which produces increased resolution because of its shorter wavelength, and the fluorescent dyes that are used emit a variety of colors, increasing contrast.
Bloom's Taxonomy: Application
Section: Microscopy
Learning Outcome: 4.6
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Which one of the following statements most accurately describes methylation?
A. Methyl groups are most often added to cytosines adjacent to guanine bases in or near the promoter sequence, increasing the probability of gene expression. B. Methyl groups are most often added to cytosines adjacent to guanine bases in or near the promoter sequence, decreasing the probability of gene expression. C. Methyl groups are most often added to adenine-thymine base pairs because they are held by only two hydrogen bonds, and this increases the probability of gene expression. D. Methyl groups are most often added to guanine-cytosine base pairs because they are held by three hydrogen bonds, and this decreases the probability of gene expression. E. Methyl groups are added to most bases in the promoter region of a specific gene so that RNA polymerase and its associated proteins will bind more efficiently.
The process whereby repeated, short stimuli provided to a hippocampal neuron have the effect of strengthening the synapse it makes with other neurons is specifically referred to as
A. long-term potentiation. B. short-term potentiation. C. neurotransmission. D. synaptic reuptake. E. None of these choices are correct.
The _____ dominates in the life cycle of bryophytes
a. gametophyte stage b. sporophyte stage c. haploid stage and sporophyte body d. diploid stage and gametophyte body e. the gametophyte and the sporophyte bodies both dominate
When individuals in a small population have difficulty finding a mate, this is referred to as
A) density dependence. B) promiscuity. C) the Allee effect. D) self thinning.