6-notes - 580.221 BME Molecules and Cells L06 Dogma of...

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580.221 BME Molecules and Cells L06 Dogma of MolBiol 1 p 1 Lecture Six – Dogma of MolBiol I -- DNA replication & DNA sequencing Outline: Central Dogma of Molecular Biology Nucleic Acids Replication Central Dogma of Molecular Biology Replication : Using a DNA template to make DNA. Key enzyme : DNA polymerase Transcription : Using a DNA template to make RNA. Key enzyme : RNA polymerase Translation : Using an RNA template to make PROTEIN. Key complex : ribosome (rRNA + proteins) Reverse transcription : Using an RNA template to make DNA (Doesn’t normally happen in the human body but some viruses do this. Key enzyme : Reverse transcriptase Information can flow back indirectly as proteins affect transcription and translation; proteins don’t normally code for RNA and RNA doesn’t normally make DNA (Some viruses can do this, creating disease.) Nucleic Acids The nucleic acids (RNA and DNA) are polymers. Their monomers are nucleotides. Nucleotide = phosphate group(s) (1-3) + sugar + base Nucleoside = sugar + base The sugar is ribose for RNA monomers, deoxyribose for DNA monomers. The deoxy group refers to the 2’ carbon of the sugar molecule, which is not involved in the condensation reactions to build the backbone of the nucleic acids. The condensation reactions give a phosphodiester bond between the 3’ and 5’ carbons of two sugars. We write a nucleotide as NTP, or N ucleoside T riP hosphate (dNTP for the deoxyribose form) or as NDP/dNDP (diphosphate) or NMP/dNMP (monophosphate). The bases used in DNA are divided into two groups : Purines (2 ring structure) – Guanine (G) and Adenine (A) Pyrimidines (1 ring structure) - Cytosine (C) and Thymine (T) In RNA, Thymine is replaced by Uracil (U)
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580.221 BME Molecules and Cells L06 Dogma of MolBiol 1 p 2 Purines pair with Pyrimidines, linking one helix to the other (Watson-Crick base pairing): A forms two hydrogen bonds with T or U G forms three hydrogen bonds with C (hence more stable base-pairing than for A-T) Can separate strands (for example during transcription) but it takes more energy to break G-C than A-T due to extra H-bond in G-C Note that the names of the nucleosides are slightly different to the names of the bases. Thus,
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This note was uploaded on 04/15/2008 for the course BME 580.221 taught by Professor Dr.vidal during the Fall '08 term at Johns Hopkins.

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6-notes - 580.221 BME Molecules and Cells L06 Dogma of...

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