What kind of letter is used for recessive traits

Lower case letters are used for recessive traits

In biology, a trait or character is a feature of an organism.  A trait refers to any genetically determined characteristic in the body. In technical terms, a genetic trait is amenable to segregation analysis rather than quantitative analysis.  Recessive traits are those that are expressed only when two copies of an allele are present in the gene.

answer; i believe that the correct answer is(d) nondisjunction during meiosis;

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.  

read more on -