The primary pacemaker of the heart is the

a. bicuspid valve.
b. tricuspid valve.
c. aorta.
d. sinoatrial node.


d

Biology & Microbiology

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The procedure in which fertilization takes place in a laboratory dish and the resulting zygote is placed in the woman's uterine tube is called

A) embryo transfer. B) ZIFT. C) RhoGAM. D) GIFT.

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Competitive inhibition of enzymes occurs

A. when a substance other than the substrate binds at the active site of an enzyme. B. when the product, or other substances, instead of the reactant, bind to the active site of the enzyme. C. when a substance binds to an enzyme at a site away from the active site. D. by blocking the production of an enzyme. E. when the product, instead of the reactant, of a reaction binds to the active site.

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lacIS encodes superrepressors, repressors that always bind to the operator and prevent gene transcription

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