There are 46 chromosomes or 23 pairs in every cell. One pair of chromosomes are the sex chromosomes. Males have an X and a Y chromosome and females have two X chromosomes. The other 22 pairs of chromosomes are called autosomes. The chromosomes contain discreet units on them called genes.
Genes are lined on the chromosome like beads on a string.
If the gene is on a sex chromosome, the condition is said to be inherited in an X-linked form. If the gene is on a autosome, the condition is said to be inherited in an autosomal manner. If one needs only one changed gene to express a condition, the condition is said to be inherited in a dominant manner. An individual with two similar genes for a given trait is refered to as a homozygote. An exception to this is X-linked recessive conditions.