What causes the AV (atrioventricular) valves within the heart to open during the cardiac cycle?

a. pressure generated by ventricular muscle contraction
b. an action potential
c. fluid pressure from the atria filling with blood
d. a pacemaker signal
e. arterial blood pressure


c

Biology & Microbiology

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If a restriction endonuclease cuts a circular DNA three times, how many fragments should there be

after the DNA is subjected to electrophoresis through an agarose gel?

a. 1 b. 2 c. 3 d. 4 e. 5

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What changes should result from using stem cells in therapeutic cloning?

A) healthy tissues B) new genomes C) model organisms D) reproductive clones

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Which of the following carbohydrates is made by plants and is not digested by humans?

A) lactose B) starch C) glycogen D) cellulose

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There are currently many similar but different species on either side of the isthmus of Panama. They probably resulted from:

A) allopatric speciation. B) sympatric speciation. C) hybridization. D) large rapid changes in their gene frequencies.

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