The picture above is a diagram of DNA. DNA consists of two twisted strands with corresponding base pairs. The chemicals in the base pairs are adenine, thymine, guanine, and cytosine. Adenine corresponds to thymine, and guanine to cytosine (Johnson, et. al). The defect of the gene HEXA is most commonly caused by a four-base-pair insertion, in which a pair of bases that doesn't belong in the protein's DNA sequence are added. This consequently interferes with the HEXA gene on the DNA strand, which contains instructions to make the HEXA protein. The defection of HEXA may also be caused by a base-pair deletion or a point mutation. Base-pair deletions occur when a base pair is missing from the DNA strands, and point mutations occur when a single base is inserted or deleted in either strand of DNA (Freedman 73).

By Andelyn