Lecture Notes-22 Biology 1004

North Arkansas College

Topic: Autosomal

Most inherited characteristics are associated with various genes on chromosomes of body cells or somatic cells - autosomal. Pairs of alleles are carried (present) in some cells (2N). An allele is an alternate form of a gene. One allele may be dominant to the other. Common characteristics such as: freckles, tone deafness, widow's peak, cleft chin, etc. are examples. Some autosomal genes (alleles) are responsible for abnormalities.

1. There are > 1500 known. A few examples are:
2. Neurofibromatosis à causes large tan spots (small tumors that are benign) to occur on body, face, and head. Disorder occurs in 1:3,000 individuals. The gene is located on chromosome 17.
3. Achondroplasia - a form of dwarfism. The individual usually does not exceed 4'4".
4. Simple glaucoma - a major cause of blindness if untreated.
5. Polydactyl - more than the normal number of fingers and toes.
6. Familial Hypercholesterol Anemia - inherited propensity for abnormally high levels of cholesterol, and increased incidence of heart disease.
7. Sickle Cell Anemia - abnormal gene for hemoglobin production. Blood cells are concave or have a sickle shape. Causes lack of O₂ transfer.
8. Huntington's Disease - a neurological disorder that leads to continual degeneration of brain tissue. Caused by excess repeats of AGC. 60 or more repeats indicates the individual will develop Huntington's by age 20.

1. Cystic Fibrosis - gene located on chromosome 7 inhibits protein that transfers chloride ions across lung membrane. Disorder causes excess mucous buildup and dryness in lungs. ~ 1:20 are heterozygous carriers (chromosome 7). Gene therapy has been successful.
2. Galactosemia - individual lacks a functioning enzyme in milk (lactase) that degrades lactose. This is a recessive autosomal recessive trait.
3. Phenylketonuria (PKU) - lack of enzyme that breaks down the amino acid phenylalanine allowing toxic ketones to accumulate.
4. Thalassemia - blood disorder most often associated with individuals of Mediterranean descent. Bone marrow becomes filled with fatty tissue. Fibrous tumor formation in blood.
5. Tay-Sach's Disease - a lysosomal deficiency disease that occurs in individuals of Jewish descent. Those affected do not produce the enzyme need to break down a lipid. This causes CNS mental retardation and blindness.

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