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2012.02.27 - Bio 1202 Lecture Review Notes.docx

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Department
Biology
Course
Biology 1202B
Professor
Gardiner/ Murphy
Semester
Winter

Description
Biology Lecture Review Notes Lecture 3 DNA Replication - Mutations  There are typically around 120 mutations in a 46 chromosome cell o 120/6billion nucleotides have a mutation, thus it is not usually serious  Only 1.5% of the whole human genome codes for mRNA and proteins, so we don’t worry about these mutations very much  We have billions of cells, so it is not common for many cells to have the same mutations Transcription (DNA  RNA)  DNA – double stranded, has thymine (T), sugar has no oxygen at C2’  RNA – single stranded, has uracil (U), sugar has oxygen at C2’  Prokaryotes have no nucleus, so transcription and translation can occur simultaneously  Eukaryotes have a nucleus, so RNA must be moved to the cytoplasm for translation to occur  Codon = 3 RNA nucleotides that are read as a triplet o AUG = methionine – start codon (start transcription) o UAA/UAG/UGA – stop codon (stop transcription)  Transcription – turning DNA into RNA o Transcription occurs in the nucleus of an eukaryotic cell o Initiation – RNA polymerase wraps around (doesn’t bind) a double stranded piece of DNA (dsDNA) at the beginning of the gene to be transcribed, unwinds it and initiates transcription at the start point o Elongation – RNA polymerase moves along the DNA, unwinding it and adding new nucleotides to the transcript in the 5’ to 3’ direction  Adds uracil instead of thymine  Behind the enzyme, the DNA reforms into a double helix  Once an RNA polymerase has started transcription and moved away from the promoter, another RNA polymerase can bind to the promoter and start transcription  This creates a hybrid of RNA and DNA – a duplex o Termination – once the end of the gene is reached, the complete RNA strand is released from the template DNA strand, RNA polymerase leaves the DNA and the DNA reforms into the double helix o You are left with a single stranded piece of pre-mRNA  DNA polymerase needed an RNA primer o RNA polymerase does not need a primer to start  mRNA is a small portion of the RNA located in t
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