1. 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.

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

3. 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.

4. 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

5. 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

6. 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?

7. 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.

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

9. Types of Mutation Substitution Deletion Insertion Inversion
Original DNA Strand

10. 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

11. 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

12. 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)

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

14. 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

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

18. 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