Haploid

  A haploid cell contains only one set of chromosomes and therefore has only one allele of each gene, this makes organisms made up of haploid cells good for genetic experiment because any mutations in the genome will have to be expressed as there are no other alleles to hide behind as there would be in a diploid cell.

In humans gametes are the haploid cells generated by meiosis, this way when fertilization occurs the cell will have a full diploid set of chromosomes.