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Chapter 4

BIL 250 Chapter Notes - Chapter 4: Tay–Sachs Disease, Mutation, Lysosome

Course Code
BIL 250
Kevin Mc Cracken

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CHAPTER 4: Gene Function
Beadle and Tatum isolated auxotrophic orange bread mold and determined their deficiencies.
This lead to the identification of the pathways to produce amino acids. They discovered that
genes act by regulating definite chemical events. This brought out the one-gene one-enzyme
hypothesis. CORRECTION: One-gene one- polypeptide hypothesis
Important notes about genes:
# of genes is not important, it is how genes are expressed
One gene can code for several polypeptides by the process of Alternative splicing
The above mentioned gives rise to similar proteins
Three important Genetic disorders with enzyme deficiencies:
1. PKA (Phenylketonuria)
1. Prevents phenylalanine from converting to amino tyrosine. Build up
2. Homo recessive (aa)
3. Result: damaged nervous system (retardation, early death)
4. Wide spread effects, Pleiotropic
5. Guthrie Test to screen
2. Type I Albinism
1. Prevents tyrosine from converting into DOPA (precursor for melanin)
2. No other known problems
2. Tay- Sach's Disease
1. Mutation of lysosomal enzyme
2. Chromosome 15 (Homo Reccessive)
3. Common in central european Jews
4. Mutation in Hex A gene
5. Leads to unprocessed gangliosides in the brain cells
6. Death by age 3-4
7. May be due to bottleneck (drastic reduction in population)
* Most enzymes are proteins but not all proteins are enzymes*
Genetic disorders coding for non-enzyme proteins:
1. ABO bloodt ype
1. MY MANZ- Karl Landsteiner
2. Alleles: IA IB and i
3. We all have H antigen and then A or B
4. Antigen signals for antibodies
5. Example of Codominance
2. Cystic Fibrosis
1. Abnormal amounts of mucous
2. Autosomal Recessive
3. Heterozygous has advantage to dehydrating diseases
2. Sickle- cell anemia
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