can be autosomal dominant (rarely cause disease) or recessive. while recessive diseases are also rare, the number of carriers are high.
a trait normally found on the sex chromosomes. most sex linked traits are located on the x chromosome. (x linked)
an individual that has a diseased gene but is phenotypically normal. most genes for recessive disease occur in heterozygotes who carry one copy of the gene but do not express the disease. by "hiding" in carriers most recessive genes for diseases survive to be passed on to the next generation.