- When DNA Mutates

MUTATION A heritable change in the nucleotide sequence of an organism’s DNA

CANCER  Two genetic causes: 1. Oncogenes – controls what type of cell a cell will be and how often it will divide. If it mutates, it becomes permanently activated and the cell will grow out of control 2. Tumor suppressor genes are normal genes that slow down cell division, repair DNA mistakes and tells cells when to die. If it mutates and doesn’t work properly, cells grow out of control.

SINGLE GENE DISORDERS  Cystic Fibrosis  Huntington’s Disease  Sickle Cell Disease

Cystic Fibrosis  A recessive disorder (usually caused by a three-base deletion causing the absence of a single amino acid out of 1480)  Affects the respiratory and digestive system and the sweat glands.  CFTR protein is defective so it doesn’t move chloride ions outside of the cell which allows thick mucus to build up and there is excess salt in the sweat  Treated with physical therapy, inhaled antibiotics, pancreatic enzyme replacement therapy and gene therapy

Huntington’s Disease  It is a dominant trait  Clumps of proteins accumulate in brain cells in the area that controls movement, emotion and thinking.  Symptoms show up between 30 and 50 years of age and get progressively worse until the person dies  Treatment help make patients more comfortable, but do not slow progression of the disease

Sickle Cell Anemia  A recessive disorder  A mutation causes the hemoglobin to form improperly so the RBC’s are rigid and have a concave shape instead of being round and flexible so they can get stuck in blood vessels and be very painful  Treatment includes antibiotics to prevent infections, folic acid to help build new cells (10-20 days versus 120 days), blood transfusions and bone marrow transplant.

CHROMOSOME ABNORMALITIES  Turner Syndrome  Williams Syndrome  Klinefelter Syndrome  Down Syndrome

Turner Syndrome  Females with a missing, incomplete or defective X chromosome  Girls are shorter than normal, ovaries fail to develop normally, stocky, arms turn out slightly, receding lower jaw, short webbed neck, heart/kidney defects  Treatment – hormone replacement therapy

Williams Syndrome  A very small amount of chromosome number 7 (less than 5 million bases) are missing  Circulatory and heart defects because gene for elastin is missing, mental retardation, unusual facial features (upturned nose, wide mouth, full lips, small chin, kidney abnormalities, low muscle tone  Treatment – symptoms are treated throughout life

Down Syndrome  Trisomy 21 – there is an extra copy of chromosome 21 therefore each gene may be producing more protein than normal  Symptoms include a flat face, small broad nose, abnormally shaped ears, large tongue, upward slanting eyes, moderate to severe mental retardation, higher risk of leukemia, hearing loss, heart defects  Treatment includes physical and speech therapy and an enriched environment to increase their capacity to learn and lead a meaningful life

Klinefelter Syndrome  Affects only males – XXY  Usually tall, less muscular body, little to no facial or body hair, most are sterile, learning disabilities are common  Treatment – hormone replacement therapy

MULTIFACTORIAL DISORDERS  Colon Cancer – if genetic, caused by mutation of a tumor suppressor gene on chromosome 5 or of a gene that fixes damaged DNA and both are inherited as a dominant trait  Breast/Ovarian Cancer – if genetic, caused by a mutation of a tumor suppressor gene on chromosome 13 or 17 and inherited as a dominant trait  Alzheimer’s Disease – people with the apoE4 gene (there are 2 other version) are at an increased risk and people with mutations of genes on chromosomes 1, 14 and 21 are linked to a rarer form of the disease