During which initial period of division in a zygote is there no increase in the overall size of the embryo?
A. Meiosis
B. Fertilization
C. Cleavage
D. Mitosis
Answer: C
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Organisms that have been genetically engineered are called ____, because they have been modified to contain genetic
information called a(n) ____ from an external source
a. transgenic; transgene b. transgenic; oncogene c. somatic; Ti plasmid d. genetically modified organisms; restriction fragment length polymorphism e. somatic; transgene
Tumor suppressors are ________
a. mutant checkpoint genes b. checkpoint genes for proteins that stimulate mitosis c. mutant oncogenes d. checkpoint genes for proteins that inhibit mitosis
Parasympathetic nervous activity has what effect on systemic arterioles?
A) vasospasm B) vasoconstriction C) vasodilation D) neither vasodilation or vasoconstriction, but may cause vasospasm E) neither vasoconstriction and vasodilation
Why did the smooth muscle in cultured strips of aorta not respond to acetylcholine by relaxing, while the smooth muscle of aortic rings did?
a) The endothelial layer in aortal strips was abnormally thickened, while in aortal rings it was not. b) Acetylcholine in the strips could not penetrate to the muscle cells while in the rings it could. c) Smooth muscle cells in aortic strips are physically incapable of relaxing under any circumstances. d) The delicate endothelial layer in aortal strips had been rubbed away during dissection, while in aortal rings it remained intact. e) Smooth muscle cells in aortic rings express acetylcholine receptors, while those in strips do not.