Question

Chemically, what makes a gene dominate or recessive?

Answer 1

if a gene producing enzyme which carry out a reaction while other allele is not able to carryout such reaction then its dominant.
in another case if allele A produce enzyme responsible for white colour and allele B produce enzyme resposible for red colour then B will be dominant.

Answer 2

can you rephrase that please

Answer 3

As adeshshendge suggests, recessiveness or dominance of an allele depends on biologic context as well as on chemical properties.

Basically, different alleles arise when random mutations occur in one copy of a gene. These mutations can be functionally neutral - that is, they have no effect on function of the protein coded by the gene; they can be loss of function mutations in which case the mutant protein is less functional than the unmutated wild type protein; or they can be gain of function in which the mutant protein is more efficient or acquires some new function relative to the unmutated wildtype protein.

Gain of function mutations tend to be dominant, in that having one mutant copy of the gene is enough to influence the phenotype; by contrast, loss of function mutations tend to be recessive in the case that one wild type gene encodes sufficient normal protein to cover for the loss of the other copy. There are exceptions to both these 'rules', but both hold in general. And there are other possible patterns (i.e., incomplete dominance) where heterozygotes have an intermediate phenotype between the two homozygous states.