Question

How many alleles do each person carry for every trait?

Answer 1

Hint: Allele is a variant form of a gene. Some genes possess a variety of different forms that are located at the same position or gene locus, on a chromosome. Humans are one of the diploid organisms as they have two alleles at each genetic locus, with one allele inherited from each parent. Each pair of alleles represents the genotype of a specific gene.

Complete answer
Genotypes are homozygous if there are two identical alleles at a locus. They are heterozygotes if the two alleles are different from one another.
Alleles contribute to the phenotype of the organism, which is the outward appearance. Alleles can be dominant or recessive. When an organism is heterozygous at a locus, carrying one dominant and one recessive allele, the organism expresses the dominant phenotype. Minor DNA sequence variations between alleles do not necessarily influence the gene’s phenotype.
Each person carries two alleles for every trait. Humans are diploid entities as they possess two alleles at each of the genetic loci. Each of the alleles is inherited from one parent. All pairs of alleles reveal the genotype of a particular gene, thus expressing the corresponding trait. Although a gene may have multiple alleles, a person can carry only two of these alleles. This happens because chromosomes exist in pairs. Example of a human trait controlled by a gene with multiple alleles is blood type.

Note:
Even though individual humans and diploid organisms carry two alleles for a given gene, multiple alleles can exist in a population level and different individuals in the population may have different pairs of these alleles. Multiple alleles make dominance relationships possible. Examples are different phenotypes of rabbits (albino, Himalayan, black, chinchilla) due to differences in alleles showing different genotypes.