Bio 130 Block 3 Notes part 2
Bio 130 Block 3 Notes part 2 Bio 130, 15017
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Bio 130, 15017
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This 6 page Class Notes was uploaded by Bennett Notetaker on Thursday March 24, 2016. The Class Notes belongs to Bio 130, 15017 at University at Buffalo taught by James Lafountain in Spring 2016. Since its upload, it has received 50 views.
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Date Created: 03/24/16
Bio 130 Block 3: PowerPoint-10 (continued) 03/29/2016 ▯ Antioxidants: Aren’t destabilized and donate electrons to free radicals Provide some protection ▯ Ultraviolet Light Contains less energy than ionizing radiation Highest wavelengths Mutations from ultraviolet irradiation induced dimerization of thymine pairs o Outcome includes: dimer introduces “kinks” into backbone o Can cause errors in transcription and replication by blocking them ▯ Mutagens Chemical compounds that significantly increase the rate of mutation above spontaneous rate Typically they’re water or fat soluble Mutation based on N base deamination Nitrous acid is derived from nitrates Sodium nitrate gets into food naturally You can minimize nitrous acid production within the body by avoiding foods with high nitrate content ▯ Deamination of adenine to hypoxanthine Nitrous acid A is converted to H N pairs with C and the H is a template for the C then it goes back to bonding with G Base substitution only appears with the ‘weird’ base H A-T pair becomes a G-C pair DNA replication is the KEY factor for these base changes ▯ Common DNA repair mechanisms Mismatch repair Direct repair Base excision Nucleotide excision Homologous recombination Non-homologous end joining ▯ ~Take home of all of this is DNA can be fixed~ ▯ Detection Damaged section recognized ▯ Excision Excision enzymes cut phosphodiester backbone and remove nucleotides ▯ Polymerization DNA Polymerase fills in the gap by adding nucleotides New DNA and old DNA need to be reconnected ▯ Ligation New DNA ends fused with old ends repairs sugar-phosphate backbone Fills in gap of new and old DNA ▯ POWERPOINT 11: ▯ OMIM An acronym that sounds for Online Mendelian Inheritance in Man, it’s a catalog of human genetic traits We will look at 3 examples o Cystic fibrosis (base deletions and base substitution) o Marfan syndrome (stop codon) o Huntington disease (base addition) ▯ ~The larger a gene, the higher the probability that it will undergo a spontaneous mutation~ ▯ ‘Average Protein’ Is about 50000 daltons or 500 amino acids o Cystic fibrosis- CFTR protein: 168000d-1480aa o Marfan syndrome- FBN1 (fibrillin): 350000d-2871aa o Huntington disease- Htt: >350000d and 3144aa ▯ Cystic Fibrosis Disease of lungs, pancreas, and skin Defects in gene for CFTR protein Chromosome 7 189000 bases 1480 amino acids Transmembrane glycoprotein Alleles pertaining to cystic fibrosis: o The C is a wild-type with a gene product called transmembrane o The c is the mutant and it’s gene product varies, defective channel or existent channel due to degradation of misfolded protein o CC=normal o Cc=normal o cc=cystic fibrosis Cell biology of cystic fibrosis o CF is an autosomal recessive trait manifested in children and is often fatal by early adulthood o CF is the consequence of a defective CFTR gene, which normally is expressed as a chloride ion channel CFTR protein: an ion channel protein, located on the mucoid luminal surfaces of epithelia One side of the epithelium would contain capillary beds or connective tissues CFTR protein functions to transport chloride ions and this happens all the time in ‘normal’ people When CFTR protein function is normal the consistency of mucus is wet (think when you have a cold) ▯ Important principles regarding the human digestive system Digestive enzymes originate in the pancreas but function within the small intestine Acinar cells in the pancreas are what synthesize digestive enzymes in their cytoplasm and then secrete into pancreatic ducts that carry them to where they will function ▯ Exocrine function of pancreas Acinar cells secrete digestive enzymes and are transported to the small intestine Epithelial cells line the secretory ducts and maintain slippery mucoid layer that aids transport ▯ Cystic fibrosis is caused by over 1000 different mutations: There are 2 critical ones o Mutation deltaF508: deletion of 3 nucleotides and loss of phenylalanine (F) at position 508 of CFTR protein o Mutation G551D: glycine (G) at position 551 is replaced by aspartic acid (D) ▯ Mutation deltaF508 Autosomal recessive allele Deletion of 3 nucleotides and deletion of phenylalanine Missense mutation causes protein misfold Misfolded protein is targeted for degradation and therefore deltaF508 CFTR is absent from affected tissues Folding of resultant polypeptide is aberrant Mucus becomes abnormally thick which indicates cystic fibrosis Mutation G551D Autosomal recessive allele Rare occurrence Glycine (non-polar) at 551 is replaced by aspartic acid Fully synthesized protein misfolds as a non-functional transmembrane protein Mutant protein has a locked gate and that’s why it lacks chloride conductivity Epithelia of affected tissues has mutant CFTR protein Causes abnormally thick mucus o Kalydeco is a drug that opens up these gates to let chloride ion transport o The mucus is then converted to a more fluid state ▯ Marfan syndrome (OMIM 154700) Autosomal dominant Locus chromosome 15 100 different mutations have been described including large reading frame deletion of 366 bases and STOP codon to yield truncated polypeptide Weak ligament, tendons and artery walls FBN1 normally binds growth factors o Alleles pertaining to Marfan syndrome w (wild type FBN) M (mutant FBN) gives dominance, even when heterozygous with wild-type recessive allele ww=normal Mw= Marfan phenotype o Pathology of Marfan syndrome Defective FBN allele does not sequester growth factors, leading to hypertrophy in arms and legs Combination of weak heart and large stature makes the tearing of aorta very common 75% of the time this mutant is passed from one parent but the parent doesn’t know they carry the mutant allele There are drugs to lower blood pressure to help with this syndrome or aorta surgery ▯ Huntington disease It’s a cytoplasmic protein found in just about every type of human cell Increases decay rate of some neurons Causes macroscopic changes in brain anatomy The hypothesis is that mutant protein misfold, forming “inclusion bodies” Autosomal dominat Loss of motor control of limbs Poly CAG codons adds misfolding to polypeptide It’s a trinucletide repeat disorder o Caused by mutation known as trinucelotide repeat expansion o During DNA replication a looped structure forms in the daughter DNA o HTT o More than 36 results in mutant protein mHtt which correlates with disease o Poly-CAG repeats in coding strand of gene leads to poly- glutamine repeats in the gene product protein from that gene w (wild type HTT) M (mutant HTT) exhibits dominance ww=normal Mw=chorea (adult onset) ▯ ▯
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