A) Both members of a human couple know that they are carriers of the galactosemia allele, a recessive metabolic disorder. None of their three children have the disease, but any of them may be a carrier. The couple would like to have a fourth child, but they are worried that the child would very likely have the disease since the first three do not. If the couple came to you with their worries, what would you tell them?
b) Would it remove any of the uncertainty in their prediction if they could find out from genetic tests whether their first three children are carriers of the disease? Why or why not?

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).