What is dominace? Why are same alleles dominant and some recessive ?

Whether an allele is dominant or recessive depends on:

Dominant & recessive trait

An allele is dominant if it is expressed in:

An organism has a gene ' X '. Its dominant allele expresses character c - 1 while it's recessive allele expresses character c - 2 This dominant allele is completely dominant over the recessive allele . It has another gene ' y ' which in its dominant form doesn't allow any expression of gene ' x ' which of these genotypes of that organism Will produce character c - 1 ?

Differentiate between dominant and recessive characters.

In………. Both dominant and recessive alleles lack their dominant and recessive relationships

In the pedigree given below, indicate whether the shaded symbols indicate dominant or recessive allele. Also give genotype of the whole pedigree.