ANT203H5 Lecture Notes - Lecture 5: Neurofibromatosis Type I, Familial Hypercholesterolemia, Brca2
Document Summary
Thousands of simple mendelian diseases (caused by mutations in one gene) have been described in humans. Individually, these diseases are not frequent, normally affecting less than 1/1,000 births. The role of genetic counselors is to give advice to individuals suffering from these diseases and to their families. Transmission of diseases in families is usually depicted using pedigrees. Carrier only makes sense when you are referring to a recessive allele. Dominant traits are which a heterozygous (with both defective and normal allele), the individual will show the disease. If this person with a disease mates with a normal female, he can still pass the defective allele 50% of the time. 50% will be homozygote for the normal allele. Usually one affected parent: by definition these diseases are rare and infrequent. Affects either sex: because this is autosomal, you can pass to either female or to male offspring. Recessive disease if you are heterozygote, you will be a carrier and phenotypically normal.
