Genetic Disorders Diseases Genetic Disordersdiseases l l l

Genetic Disorders & Diseases

Genetic Disorders/diseases l l l Genetic disorders/diseases are caused by mutations. A mutation is any type of change in genetic material. Mutations are caused by: – Radiation l – X-rays, sun exposure Chemicals l May contain toxic substances

Mutations l You can pass on mutations to your offspring only if the mutation is in your sex cells!!

Mutations l Mutations in your body cells can be passed on to other cells of your body only!! – Cancer (not inherited)

Types of Mutations 1. Whole chromosomes are missing OR there are extra chromosomes. l l This is caused by disjunction which happens during meiosis when chromosomes did not segregate or separate and distribute to the gametes properly. Examples: Trisomy 13 l Trisomy 21 l Turner’s Syndrome l Kleinfelter’s Syndrome l

Trisomy 21 – Down’s Syndrome l Extra copy of chromosome 21 The incidence of Down syndrome is estimated at 1 per 800 to 1, 000 births, although these statistics are heavily influenced by the age of the mother.

Trisomy 13 l Chromosomal condition that is associated with severe mental retardation and certain physical abnormalities. small eyes that may exhibit a split in the iris – an opening in the roof of the mouth (a cleft palate) and/or a cleft lip, – weak muscle tone – skeletal abnormalities, Affected individuals rarely live past infancy because of the lifethreatening medical problems associated with this condition – Trisomy 13 affects approximately 1 in 10, 000 newborns. The risk of having a child with trisomy 13 increases as a woman gets older.

Turner’s Syndrome l l One sex chromosome Underdeveloped sex characteristics One in 2500 births

Kleinfelter’s Syndrome l l 2 XX’s 1 Y Underdeveloped sex organs

Types of Mutations 2. Sections of Chromosomes are missing or misplaced. Inversion mutation Duplication Deletion

Sections of Chromosomes are missing or misplaced con’t… Translocation

Genetic Disorders l Genetic Disorders can also be caused by recessive defective alleles: – Each parent carries 1 recessive allele. Offspring may inherit the defective allele from both parents and get the disease. l l l Sickle cell Phenylketonuria Tay-Sachs Cystic Fibrosis Huntington’s Disease

Sickle Cell l Your Genes, Your Health l http: //www. ygyh. org/index. htm

Phenylketonuria - PKU l l Most children are screened at birth for PKU Can lead to mental retardation Smaller than normal head Epilepsy Deficiency in the enzyme phenylalanine hydroxylase (PAH). This enzyme is necessary to metabolize the amino acid phenylalanine to the amino acid tyrosine

Tay-Sachs Disease l Your Genes, Your Health

Cystic Fibrosis & Huntington’s Disease l Huntington's Disease – dominant disease, you need to inherit only 1 copy of the disease to have it. Abnormal protein is produced and you start to kill brain tissue occurs around middle age, mood swings, paralysis, loss of memory, uncontrolled movements and eventually death – l 1 in 20, 000 in western hemisphere, 1 in 1 million in Asia Cystic Fibrosis – recessive disorder, a genetic mutation stops the production on a protein of cells in the lung, pancreas or other organ – Affects about 1 on 2500 births in the US