Mutations Affecting Humans Genetic Diseases

Genetic Disorders Thousands of genetic disorders are inherited as simple recessive traits from benign conditions to deadly diseases albinism cystic fibrosis Tay sachs sickle cell anemia PKU

Albino People

Albinism Occurs in Animals

Chromosomal Mutations Deletion in Chromosome 5

Cystic Fibrosis A defective gene on chromosome 7 (resulting from the deletion of only 3 bases) is inherited as a recessive trait. The main effect seems to be the body’s excessive production of an abnormally thick and sticky mucus. This kind of mucus can block the trachea which can lead to severe breathing issues and can cause bacterial infections in the lungs. The long-term buildup of the mucus and lung infections can lead to permanent lung damage such as; the formation of scar tissue, and the growth of cysts.

Sickle Cell Anemia Substitution of one amino acid in polypeptide chain hydrophilic amino acid hydrophobic amino acid 8

Sickle Cell Anemia Autosomal recessive Found most often among people of African ancestry Blood cells sickle (change shape) when oxygen-deprived (exertion, increase in altitude) and block tiny capillaries Causes sickle cell event – pain and immobility and death of tissue ( dangerous if in organ) Treatment – hospitalization and oxygen Carriers are resistant to malaria

Tay Sachs Disease Single defective enzyme Heterozygote carriers (Hh) do not have disorder, but are resistant to Tuberculosis Fatty substance builds up in neurons Gradual paralysis and loss of nervous function by age 4-5 Especially common in Jewish population (central and eastern European descent), up to 11% are carriers

Huntington Disease Autosomal dominant Symptoms do not appear until age 30-40. Death takes about 5-10 years No treatment, no cure – but there is a test to see if you have it before symptoms begin Results in mental impairment and uncontrollable spastic movements

PKU (Phenylketonuria) Can’t break down amino acid phenylalanine (missing critical enzyme) Phenylalanine builds up and interferes with nervous system leading to mental retardation and even death Early screening (urine test)  phenylalanine restricted diet for children with disorder

Down’s Syndrome Karyotype

Down’s Syndrome Trisomy 21

Klinefelter’s Syndrome XXY

Turner’s Syndrome Karyotype

Turner’s Syndrome

These disorders result from NONDISJUNCTION Failure of chromosomes to separate normally during meiosis – Eggs or sperm get one too many chromosomes or one too few. Ex – Down syndrome has one extra #21 Klinefelter has one extra X chromosome Turner has one too few – only one X

Polydactyly

The Wolf Boy (Danny Gomez) Hypertrichosis

Genetic Testing Amniocentesis and Chorionic Villus Sampling Sample of amniotic fluid or placenta Karyotyping Taking a picture of the chromosomes in a cell