Chromosome 3 of corn carries three loci (b for plant-col- or booster, v for virescent, and lg for liguleless). a test- cross of triple recessives with f1 plants heterozygous for the three genes yields progeny having the following genotypes: 305 + v lg, 275 b + +, 128 b + lg, 112 + v +, 74 + + lg, 66 b v +, 22 + + +, and 18 b v lg. give the gene sequence on the chromosome, the map distances between genes, and the coefficient of coincidence.

Choose the incorrect statement (a) the motor end plate membrane is only capable of generating graded potentials, but it is contiguous with the skeletal muscle sarcolemma, which can generate action potentials. (b) propagation of an action potential through the t-tubules into the sarcoplasmic reticulum triggers the release of ca++ into the cytoplasm of a skeletal muscle fiber. (c) the generation of suprathreshold endplate potentials in multiple muscle fibers could be due to the increased frequency of action potential generation at the axon hillock of a single motor neuron. (d) a greater amount of ach would be found in the presynaptic vesicles of a motor unit that fired several action potentials after exposure to botulinum toxin, than in a motor unit that fired several action potentials after exposure to the venom of the krait snake (which contains α-bungarotoxin).