Which microscope forms an image from two sets of light rays, one from the light source and the other diffracted from a structure in the specimen?
a) Fluorescence microscope
b) Phase-contrast microscope
c) Darkfield microscope
d) Confocal microscope
Ans: b) Phase-contrast microscope
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Rubisco has 16 subunits joined together to make a functional unit. Eight of the subunits are large, the
other 8 are small. What does this tell you about this protein's structure?
a. It is an example of a protein having quaternary structure. b. The protein has tertiary structure and domains but no quaternary structure. c. The primary sequence of all 16 subunits is identical, which is a unique property of enzymes participating in photosynthesis. d. The subunits each have 8 alpha helices in order to bind to CO2 and RuBP. e. It's an enzyme that is extremely resistant to denaturation.
Experiments by Stanley Miller in the 1950s demonstrated that the first organic molecules on earth
A) were nucleic acids such as RNA and DNA. B) most likely formed in an extraterrestrial environment and were deposited on earth via asteroids. C) could have formed abiotically in a reducing atmosphere containing hydrogen, methane, ammonia, and water vapor. D) were catalysts composed of simple amino acids. E) were catalysts composed of simple amino acids and most likely formed in an extraterrestrial environment and were deposited on earth via asteroids.
Which statement is NOT true of the T cells?
A. T cells require presentation of antigens by macrophages before they are able to recognize the antigen. B. T cells change into plasma cells and produce antibodies when stimulated. C. T cells mature in the thymus. D. T cells carry receptor molecules on their cell surfaces.
Gene silencing has been effective in mouse models of HD that are heterozygous for the mHTT gene. The results are promising as ________
A) the injection into one side of the mouse brain affected both sides of the brain B) both mHTT and HTT were down regulated C) the study demonstrated the ZFN only targeted the mHTT allele and left the normal HTT expression level unchanged D) the injection into both sides of the mouse brain resulted in reduced mHTT