Suppose pcr is used to amplify a single dna marker on human chromosome 21. this is a way to identify individual chromosomes, such as paternal and maternal chromosome 21 from each parent. further suppose that a couple who have a child with down syndrome (trisomy 21) is examined for this marker. the mother has marker alleles of 310 and 380 bp. her mate has marker alleles of 290 and 340 bp. what combinations of pcr bands would be expected in their child with down syndrome if nondisjunction occurred in a. maternal meiosis i b. maternal meiosis ii c. paternal meiosis i d. paternal meiosis ii

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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this is math not biology xd

a scenario where a cell may be needed to perform a form of endocytosis is when transporting large molecules. a scenario where a cell may be needed to perform a form of exocytosis is when releasing the large molecule from the cell.