This lecture focused on the single gene disorders that are classified as autosomal dominant and recessive. A single gene disorder is one in which the disease is largely caused by mutations at single genetic locus. But our view of single gene disorders is changing.
Geneticists now argue that all diseases are partly genetic and all are partly environmental.
If a person has two different mutant alleles, they may be referred to as a compound heterozygote. When talking about a given genetic locus, we distinguish between genotype and phenotype. A person s genotype consists of the alleles present at that locus. The phenotype is the observable expression of those genes. Dominant disorders are those that are expressed in individuals who carry one normal and one defective allele.