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DNA

DNA. Deoxyribonucleic acid. DNA structure. 1953 – James Watson and Francis Crick, at Cambridge University, England Double Helix – (twisted ladder) phosphate and sugar alternate on the sides Bases are held together by hydrogen bonds Complimentary bases: Adenine - thymine

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DNA

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  1. DNA Deoxyribonucleic acid

  2. DNA structure 1953 – James Watson and Francis Crick, at Cambridge University, England Double Helix – (twisted ladder) phosphate and sugar alternate on the sides Bases are held together by hydrogen bonds Complimentary bases: Adenine - thymine Cytosine – Guanine 1949 – Chargaff determined: % A = % T, % C = % G

  3. DNA Replication • Helicase (an enzyme) separates the DNA by breaking the hydrogen bonds (DNA unzips) • DNA polymerase brings in nucleotides to bond with their complimentary bases • DNA polymerase drops off, 2 DNA molecules are formed

  4. Human chromosomes are very long. • Replication occurs a 50 nucleotides per second. • It would take 53 days to replicate 1 chromosome therefore: replication forks occur at many sites simultaneously to allow for rapid replication

  5. RNA – ribonucleic acid • contains Uracil, not thymine • contains Ribose, not deoxyribose 3 types: • Messenger RNA (mRNA) - brings messages from the nucleus into the cytoplasm - ribbon shape - contains codons

  6. 2. Ribosomal RNA (rRNA) - makes up the ribosome 3. Transfer RNA (tRNA) - brings amino acids to the ribosome - found in the cytoplasm - t-shaped - has anticodon

  7. Transcription – making mRNA • RNA polymerase (an enzyme) separates the DNA by breaking the hydrogen bonds (DNA unzips) • RNA polymerase brings in RNA nucleotides to bond with their complimentary bases along one side of the DNA molecule • RNA polymerase drops off, mRNA moves away, DNA molecule closes

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