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Salty sweat due to altered salt secretion in sweat ducts

Symptoms of cystic fibrosis. Salty sweat due to altered salt secretion in sweat ducts. Mucus-clogged Airways; Severe Respiratory infections. Lung. Pancreas. Infertility in males due to clogged sex ducts. Testis. Cell lining ducts of the body. Cystic Fibrosis

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Salty sweat due to altered salt secretion in sweat ducts

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  1. Symptoms of cystic fibrosis Salty sweat due to altered salt secretion in sweat ducts Mucus-clogged Airways; Severe Respiratory infections Lung Pancreas Infertility in males due to clogged sex ducts Testis Cell lining ducts of the body

  2. Cystic Fibrosis • A single faulty protein is connected to the symptoms • In 1989 the gene was mapped to chromosome #7

  3. Our Goals • To determine the connection between the symptoms associated with cystic fibrosis and DNA – How? • Learn how DNA replicates • Understand the genetic code and how the instructions in a gene are used to make a protein

  4. Central Dogma of Biology

  5. DNA and RNA: Polymers of Nucleotides • Nucleotide: base + sugar + phosphate

  6. Fig 10.2

  7. T A single strand of DNA A C Sugar- phosphate backbone G

  8. DNA vs. RNA Nucleotides • Four nucleotides are found in DNA • Differ in their nitrogenous bases • Adenine (A), Thymine (T), Cytosine (C), Guanine (G) • Sugar: • Four nucleotides are found in RNA • Uracil instead of Thymine • Adenine (A), Uracil (U), Cytosine (C), Guanine (G) • Sugar:

  9. DNA Structure • Consists of 2 strands joined together by weak hydrogen bonds • Rungs of the ladder are hydrogen bonded N-bases DNA is like a rope ladder twisted into a spiral Twist Fig 10.4

  10. Base pairing in DNA: Figure 10.5

  11. What is a gene? • The kind of proteins an organism makes helps to determine it’s phenotype

  12. The order of bases in a gene determines...... • The sequence of amino acids in the protein it codes for, which determines...... • the organism's phenotype—the physical and biochemical characteristics of an organism.

  13. DNA replication Questions to answer • When during the cell cycle does it occur? • What do we start with and end with? • Where does it occur in a cell? • What’s needed for it to occur? • What is the sequence of events? • Why is it said to be semi-conservative? • What does proofreading mean? • What does the proofreading?

  14. DNA Replication Fig 10.6

  15. 1 3 4 2 • Parent molecule has 2 complementary strands of DNA • Enzymes initiate the breaking of the H-bonds, separating the double helix • Free nucleotides base – pair to parent strands (A-T, G-C) using DNA polymerase enzyme • Each “daughter” strand consists of one parental strand and one new strand –

  16. DNA can be damaged – eg. by ultraviolet light • The enzymes (e.g. DNA polymerase) can repair the damage: • Is the damage always repaired? Consequences?

  17. The Flow of Genetic Information: DNA to RNA to Protein • Transcription: • Translation: ribosomes translate mRNA into protein—a chain of amino acids Fig 10.9

  18. CF phenotype Genes determine which proteins a cell can make Proteins control phenotype e.g. CFTR Gene codes for CFTR protein

  19. CFTR Protein: The cystic fibrosis transmembrane regulator protein Cytoplasm of cell lining duct or lungs CFTR Protein • Pumps chloride ions (salt) out of cells lining ducts of the lungs • What are the consequences when CFTR doesn’t work? Chloride ions CFTR Protein Cell membrane Inside of duct or Air sac in lungs

  20. The order of bases in a gene determines the order of amino acids in the protein it codes for Fig 10.10

  21. Why are proteins so important? • Enzymes: catalysts for nearly all chemical reactions in cells; Determine what cells can make and digest • Structural components: • Receptors on cell surface • Hormones: e.g. insulin, growth hormone, prolactin • Transport: e.g. hemoglobin, spindle fibers • Immune system: antibodies

  22. Transcription: copying DNA into RNA Questions to answer: 1. What do we start with and end with? 2. Where does transcription occur? When? 3. What is needed for transcription to occur? 4. What is the sequence of events?

  23. An RNA Nucleotide Phosphate Base (Uracil, U) Sugar: ribose This oxygen is absent in deoxyribose

  24. RNA • Base – pairing: • Single stranded • Sugar = ribose (one more oxygen than deoxyribose)

  25. Stages of Transcription Fig 10.13b

  26. Fig 10.13a

  27. Transcription • Initiation - RNA polymerase enzyme binds to the promotor (section of DNA indicating “start of a gene”) • Elongation – RNA polymerase catalyzes base pairing on the template strand (U-A, G-C) • Termination – RNA polymerase reaches the “stop” sequence and the new mRNA is released. • mRNA processing –non-coding regions of the mRNA are removed and the mRNA leaves the nucleus.

  28. Fig. 10.14 Step 4 mRNA processing

  29. Translation: Ribosomes reading mRNA to produce a polypeptide Questions to answer • What do we start with and end with? 2. Where does translation occur? 3. What is needed for translation to occur? • What is the sequence of events? • What are the roles of mRNA, ribosomes, start codon, tRNA, anticodons, stop codon?

  30. How do ribosomes read the code?

  31. The genetic code Fig 10.11 Codon = 3 letter section of mRNA that codes for one amino acid

  32. Transfer RNA: tRNA Fig 10.15 • tRNA • Matches amino acids with codons in mRNA using anticodons

  33. A portion of an mRNA molecule attached to a tRNA Codon on mRNA mRNA Each Codon specifies a specific tRNA—amino acid complex Amino acid

  34. Stages of translation 1. Initiation – mRNA start codon binds to tRNA anticodon; Ribosome binds to both

  35. 2. Elongation • tRNA brings specific AAs to the ribosome as mRNA passes through the ribosome (codon – anticodon recognition)

  36. 3. Termination – Ribosome reads an mRNA stop codon (no tRNA with anticodon). mRNA and protein detach from the ribosome

  37. Explaining the symptoms of CF • Mucus build-up in the lungs • Lung infections (e.g. pneumonia) • Male sterility (blocked vas deferens) • Salty sweat • Trouble digesting food (blocked pancreatic duct)

  38. Explaining the symptoms of CF • In CF, the faulty CFTR protein never makes it to cell membrane

  39. Understanding Cystic Fibrosis at the Cellular Level How does CFTR protein get from where it’s produced to its home in the cell membrane? • Where is the CFTR protein produced? • Where does it go for modification? • How does it get there? • How does the modified CFTR protein get to the plasma membrane? • The defective CFTR protein is recognized at the ER as defective • Where is the defective CFTR protein sent?

  40. CF symptoms may be mild or severe CFTR Gene Several hundred different mutations are associated with CF

  41. What’s a Mutation? • Any change in the nucleotide sequence of DNA • Types of Mutations • Mutations may Result from: • Random errors in DNA replication • Viruses • Chemicals/toxins (cigarette smoke) • Radiation (e.g. U.V. light, X-rays)

  42. DF508 deletion: the most common cause of cystic fibrosis

  43. Mutation responsible for Sickle Cell Anemia: nucleotide substitution Glu Val

  44. 3 Types of Mutations:Base Substitutions, Insertions or Deletions • Base substitutions • May result in changes in the amino acid sequence in a protein, or • May be silent (have no effect) – Why? Substitute C for U Met Lys Phe Gly Ala AACGGUUAUCCU Asn – Gly – Tyr – Pro Met Phe Ser Ala

  45. Changes the reading frame of the genetic message mRNA Types of Mutations: Base Insertions and deletions Protein Met Lys Phe Gly Ala (b) Nucleotide deletion Met Lys Leu Ala His

  46. They are the source of the rich diversity of genes in the living world • They contribute to the process of evolution by natural selection • Although mutations are often harmful

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