The number of major histocompatability (MHC) protein combinations possible in a given population is enormous. However, an individual in that diverse population has a far more limited array of MHC molecules because _____
A) the MHC proteins are made from several different gene regions that are capable of rearranging in a number of ways
B) MHC proteins from one individual can only be of class I or class II
C) each of the MHC genes has a large number of alleles, but each individual only inherits two for each gene
D) once a B cell has matured in the bone marrow, it is limited to two MHC response categories
E) once a T cell has matured in the thymus, it can only respond to two MHC categories
Answer: C
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Cells are often ground up with abrasive to get to their internal enzymes/molecules, followed by removal of the abrasives. Here are three situations and three outcomes. What is the correct interpretation of the results?
In situation #1, radioactive amino acids are added to cell material, and radioactive proteins are produced. In situation #2, radioactive amino acids, cell material, and the enzyme DNAse (degrades DNA) are added together. Radioactive proteins are still produced. In situation #3, the ground-up cell material is allowed to sit for 24 hours before radioactive amino acids and DNAse are added to it. No radioactive protein is produced. What is the most likely interpretation? A. RNA polymerase has no activity after 24 hours, so no mRNA is transcribed and translated into radioactive proteinsin the last scenario. B. The radioactivity in the amino acids is altering/degrading the tRNA molecules, leading to no protein production in the last scenario. C. Natural RNAses present in the ground-up material will degrade any existing mRNAs in that 24-hour interval. Added DNAses breakdown DNA so that new RNAs are not synthesized.This will lead to a loss of capability to translate protein in the last scenario. D. The results are not interpretable from the information given.
In order for a cell to respond to the signaling molecule epinephrine, it must ____
a. have ion channels b. have a lipid bilayer that allows the response to occur c. have receptors exposed on the inner plasma membrane surface d. have receptors exposed on the plasma membrane surface e. have nuclear membrane receptors
The vital capacity is indicated by
a. A + D. b. A + D + E. c. C + E. d. A + B + C + D. e. A + C + D.
Which type of neuron is found only in the brain and spinal cord?
A) sensory neuron B) interneuron C) motor neuron D) glial cell