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12 dna organization


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12 dna organization

  1. 1. What’s the difference between prokaryotic & eukaryotic DNA?
  2. 2. Prokaryote vs. Eukaryote DNA Prokaryote Eukaryote circular linear not contained in contained in nucleus nucleus cellular function can uptake smaller circular DNA pieces compromised with extra DNA
  3. 3. Prokaryote DNA
  4. 4. DNA Organization chromatin – DNA strands populated with proteins; found in eukaryotes Prokaryotic DNA is commonly referred to as being “naked”, with no proteins bound. histones – proteins that bind to eukaryotic DNA DNA backbone has a negative charge histones bind to DNA due to a positive charge
  5. 5. DNA Organization Three levels of DNA organization: nucleosome 2. solenoid fibre 3. supercoiling 1.
  6. 6. 1. Nucleosome Approximately every ~200 bp of DNA is associated with a group of histones to create a nucleosome. single histone nucleosome DNA strand 8 histones 200 bp
  7. 7. 2. Solenoid Fibre The solenoid fibre is organized in a stacked spiral of nucleosomes. It is also known as the 30 nm fibre.
  8. 8. 3. DNA Supercoiling supercoiling – twisting and compacting to form mitotic chromosomes
  9. 9. Chromatin Packing Euchromatin Heterochromatin eu – true hetero – different loosely packed DNA tightly packed DNA regions which allows transcription to readily occur regions with little transcription
  10. 10. Chromatin Packing
  11. 11. Chromosomal Sections centromere region where sister chromatids are connected made up of repetitive sequences telomere ends of chromosomes made up of repetitive sequences
  12. 12. Chromosome Structure Centromeres split chromosomes into two arms: p arm – petit arm q arm – long arm
  13. 13. VNTRs (microsatellites) variable number tandem repeats (VNTRs) – repetitive DNA sequences in coding and regulatory regions repeating sequences can be of any length  sequence repeated a different number of times  repeats that exceed a normal range can cause disease  Huntington’s Disease  expansion of a CAG triplet repeat stretch Repeats Disease < 27 - 27 – 35 - 36 – 39 +/- > 39 +