AIM: What causes genetic disorders. Do Now: What are genetic disorders AIM: What causes genetic disorders? Do Now: What are genetic disorders? Explain how a genetic disorder is “passed on” to an individual.

There are two causes of genetic disorders: Chromosome mutations Gene mutations

Chromosome Mutation: Nondisjunction- occurs when homologous Causes a change in chromosome number. Nondisjunction- occurs when homologous chromosomes or sister chromatids fail to separate during meiosis.

Trisomy Vs Monosomy: Trisomy 21 Monosomy X 3 Copies of a 1 copy of a Chromosome 1 copy of a homologous pair Down Syndrome Turner Syndrome

What causes nondisjunction to occur? No one really knows for sure, but the older the age of the mother the greater the likelihood of having a child with Down Syndrome. Trisomy 21

Gene Mutations Mutations (changes in the genetic code) that can lead to changes in the amino acid sequence and ultimately to the overall shape of the protein. Why?

Gene Mutations: Is due to a change in the nucleotide sequence of DNA. They can involve large regions of a chromosome or just a single nucleotide pair.

What causes mutations errors in DNA replication? Chemicals UV Radiation X-Ray radiation

Types of Mutation Substitution Deletion Insertion Inversion Original DNA Strand

Substitution and Deletion Mutations Substitution – One nitrogenous base is substituted for another. DNA CCC CAA GAT GCG mRNA GGG GUU CUA CGC Deletion – One nitrogenous base is deleted (removed). DNA CTC AAG ATG CG mRNA GAG UUC UAC GC

Insertion and Inversion Mutations Insertion – Extra nitrogenous bases are added to the genetic code. DNA CCT CTA AGA TGC G mRNA GGA GAU UCU ACG C Inversion – The genetic code is inverted or reversed. DNA CCT CAA TAG GCG mRNA GGA GUU AUC CGC

Point and Frame Shift Mutations Point mutation A change in ONE nitrogenous base, the overall number of bases stays the same (Substitution or Inversion) Frame shift mutation A change in the number of overall nitrogenous bases in the genetic code (Addition or Deletion)

Recessive v Dominant genetic disorders: REMEMBER: YOU HAVE TWO COPIES OF EACH CHROMOSOME One from mom One from dad

Recessive You need two mutated copies of the gene to show symptoms of the disorder Mom and Dad were both carriers- each of them passed down a mutated gene to you What is a carrier? You have one mutated copy of the gene You will not show symptoms but you could pass that mutated copy to your offspring

Dominant You only need one mutated copy of the gene to show symptoms of the disorder

1. Achondroplasia - most common genetic cause of dwarfism 2. Albinism - little or no production of melanin in hair, skin, and iris of the eyes 3. Bloom Syndrome - high frequency of breaks and rearrangements in the chromosomes 4. Cystic Fibrosis - autosomal recessive disorder secreting mucus and sweat 5. Down Syndrome - abnormal cell division of chromosome 21 6. Duchenne Muscular Dystrophy - rapidly gradual muscle weakness and damaged muscular tissue in the pelvis and legs 7. Fragile X Syndrome - inherited form of mental retardation 8. Galactosemia - body’s inability to break down galactose 9. Hemophilia - body’s inability to control bleeding (interior or exterior, or both) 10. Klinefelter Syndrome - abnormal testicular evolution and decreased fertility 11. Lesch-Nyhan Syndrome - deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT) Neurofibromatosis - development of tumors along the different nerves and evolution of non- nervous tissues, like skin and bones Noonan Syndrome - heart malformations, short stature, characteristic facial features, impaired blood clotting, and indentation of the chest Osteogenesis Imperfecta - weakened muscles, brittle bones, curved spine, and impaired hearing 15. Phenylketonuria - mental retardation, seizures, or brain damage 16. Porphyria - accumulation of porphyrin or its precursors in the body 17. Sickle Cell Anemia - blood disorder causing sickling of the red blood cells 18. Tay-Sachs Disease - damage of the nerve cells in brain and spinal cord 19. Turner Syndrome - lack of either one whole or a part of an X chromosome 20. Wilson’s Disease - body’s inability to get rid of excess copper in the body