How Are Diseases Inherited?
DNA is a double-stranded molecule that is twisted in a spiral shape, known as a double helix. DNA is made of chemicals called nucleotides that occur in pairs: adenine (A) with thymine (T), and guanine (G) with cytosine (C). Inherited genetic disorders that are carried on the sex chromosomes are referred to as sex-linked. Disorders carried on the other chromosomes are referred to as autosomal (aw-to-SOME-al). In general, autosomal disorders are likely to affect males and females equally, but sex-linked disorders usually affect males more often than females. This gender difference has to do with the fact that males have only one X chromosome. The X chromosome Three common inheritance patterns. carries genes for which there is no second copy on the Y. Therefore, a male has only one copy of these genes. If his copy is damaged or defective, he has no normal copy to override or mask the defective one. Depending on the problem with the gene, the result can be an X-linked disorder.
