A single, long double-stranded DNA encoding cellular function. Double-stranded DNA bound by many proteins containing a linear array of genes. An RNA template for protein synthesis. All loci have one or two alleles. Some loci have many alleles.
Some loci have many alleles that are common in a population.
Dominant alleles can cause genetic disease. All recessive alleles cause genetic disease. Alleles that cause genetic disease are common in most populations. It is not possible diagnose genetic disease before it develops. Alleles arise by mutation.