The terms anomaly, abnormality, disorder, defect, disease, and syndrome are not used consistently and do not have precise definitions. Each chromosome is comprised of 2 extremely long DNA molecules in combination with chromosomal proteins . Genes are defined by intervals along one of the DNA molecules. The location of the gene is called the locus. Most genes carry information which is necessary to synthesize a protein .
Alleles are different variants of a particular gene.
This protein may be a structural constituent of a given tissue. It may be an enzyme which catalyzes a chemical reaction, or it may be a hormone. There are also many other potential functions for proteins. If a gene is abnormal, it may code for an abnormal protein or for an insufficient amount of a normal protein. Since the autosomal chromosomes are paired, there are 2 copies of each gene.