Genetics - Some definitions before we get into the nitty gritty

Gene: a segment of DNA that codes for one characteristic

Locus:  the physical position on a strand of DNA where a gene is found

Allele: an alternative form of a gene (one member of a pair) that is located at a specific location on a specific  chromosome

Wildtype allele:  the most commonly occurring allele in a population

Phenotype:  the appearance, structural and functional characteristics of an organism

Genotype:  the genes of an organism that produce the phenotypic characteristic

Dominant allele:  an allele that produces the same phenotypic characteristic, whether its paired allele is the same or different.

Recessive allele: an allele that only produces its characteristic phenotype when its paired allele is identical.

Haploid: an organism (or cell) with only one copy of its genetic material (DNA)

Diploid: an organism (or cell) with two copies of its genetic material (DNA)

Homozygote: a diploid cell in which the alleles for a given gene are identical.

Heterozygote: a diploid cell in which the alleles for a given gene are different.