Advances in molecular systematics show that whisk ferns and horsetails are the closest living relatives of
A. mosses.
B. club mosses.
C. seed plants.
D. gymnosperms.
E. ferns.
E. ferns.
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Threshold potential refers to the membrane potential required to:
A. open voltage-gated potassium channels. B. initiate an action potential. C. open voltage-gated sodium channels. D. initiate an action potential AND open voltage-gated sodium channels.
Localized injury or death of tissue resulting from repeated injections of an antigen into a person with high levels of circulating specific antibody is known as
A. farmer's lung. B. German measles. C. serum sickness. D. an Arthus reaction.
Darnell and Tinaka are each carriers of an autosomal recessive disorder that is lethal in early childhood. They want to have a child who is free of the disease, so they have preimplantation genetic diagnosis. Unfortunately, their child has the disease. A scientific explanation is that
A) the blastomere that was tested had undergone a somatic mutation, making it not representative of the rest of the embryo. B) Darnell was not really the father. C) the 7 cells of the remaining embryo each underwent a mutation, so the sampled cell was not representative. D) Darnell or Tinaka is really homozygous recessive, and not heterozygous.
Some enzymes have a receptor site that is other than the active site. This is also referred to as a(n) ____ site
a. sensitive b. allosteric c. inhibitive d. reversible e. competitive