For every trait, there are two types of characters - dominant and recessive which are determined by the combination of the alleles for a given gene.
Each gene has 2 types of alleles- one is the dominant allele which always expresses itself that is in both homozygous and heterozygous conditions whereas the other one is the recessive allele which can only express itself in the homozygous conditions.
In Mendel's experiments when he crossed plants with different traits he observed that in the F1 generation there was always a single trait that was getting expressed and it was the trait that was being coded by the dominant allele.
The pH of an amino acid is determined by the nature of the side chains of that amino acid. If the side chain of an amino acid contains amine functional group the amino acid will be basic. The acidic amino acids are acidic because they have carboxylic acid functional groups at their side chain.
