The principal advantage of air sacs in birds is that:
A. They increase the surface area through which oxygen is absorbed.
B. They provide better aerodynamic lift.
C. They minimize the absorption of harmful gases.
D. They promote continuous flow of air through the lungs thereby enhancing metabolism by making oxygen more readily available.
E. All of the choices provided are correct.
D. They promote continuous flow of air through the lungs thereby enhancing metabolism by making oxygen more readily available.
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To create a mouse model of the human disease Hemophilia A, in which a nonfunctional factor VIII protein results in a blood clotting deficiency, _____
a. a cloned mutant FVIII gene is inserted into fertilized mouse eggs, which are then transferred to a foster mother for gestation and birth b. a cloned normal FVIII gene is inserted into fertilized mouse eggs, which are then transferred to a foster mother for gestation and birth c. mice with similar, naturally occurring, clotting deficiencies are cloned d. embryonic stem cells are harvested from mouse blastocysts, and grown in the lab to produce blood cells for experimental research e. adult mice are infected with bacteria that contain a copy of a mutant human FVIII gene
A genetic disease that causes death in infancy and has an autosomal recessive inheritance pattern can persist in a population because: Check all that apply.
_____ it can be passed on to the next generation by a heterozygous carrier. _____ if both parents are carriers, they have a 50% chance of having normal children. _____ only homozygotes for the abnormal allele will have the disease. _____ individuals with one abnormal allele do not show symptoms of the disease.
Gs? nucleotide exchange is stimulated by a ________, whereas Ras nucleotide exchange is stimulated by ________
Answer: GPCR/EGF receptor; Sos
Water potential is generally most negative in which of the following parts of a plant?
A) mesophyll cells of the leaf B) xylem vessels in leaves C) xylem vessels in roots D) cells of the root cortex