During ______, crossing-over sometimes occurs between nonsister chromatids of a tetrad.
a. cell division
b. mitosis
c. meiosis
Answer: c. meiosis
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UV light is necessary for the production of which vitamin?
a. folate b. vitamin A c. vitamin C d. vitamin D e. vitamin E
The level of carbon dioxide in the blood is monitored by nerve tissue. If you exercise strenuously, the increase in cellular respiration consumes oxygen from the blood and produces surplus carbon dioxide removed in the blood. Since this physical exertion requires faster breathing to replenish oxygen supplies and carry away carbon dioxide, the carbon dioxide sensors result in signals from the brain to increase breathing rate. After you have rested, and carbon dioxide levels are back to normal, your breathing rate decreases too. This is an example of
A. a positive feedback loop that stimulates a response opposite to the stimulus. B. a response to a sensory impulse that causes a muscle or gland to react. C. the dynamic interplay between events that tend to change the internal environment and events that tend to keep it the same. D. a negative feedback loop that stimulates a response similar to the stimulus. E. the dynamic interplay between events that tend to change the internal environment and events that tend to increase the changes.
Which of the following components is/are found in the cell walls of gram-positive bacteria but NOT gram-negative bacteria?
A. Cytoplasmic membrane B. Lipopolysaccharide C. Outer membrane D. Peptidoglycan E. Teichoic acid
Which of the following is a complication that may result from a Streptococcus pyogenes skin infection?
A) a carbuncle B) a sty C) shingles D) scalded skin syndrome E) erysipelas