University:
Amherst College
Course:
BIOL 330 | Biochemical Principles of Life at the Molecular Level
Academic year:

2010
Views:

99

Pages:

14
Author:

pigamdomo81d

Chemical Biology 03 Oct 15, 2010 Central Dogma –III in Eukaryotes 1o transcript (“pre-mRNA”) Modifications of mRNA • add a 5’ cap • add a 3’end tail • remove introns mature mRNA ready for translation The Genetic Code: (codons in 5’->3’) The GENETIC CODE to Translate from RNA to PROTEIN: triplet code: set of 3 nucleotides (“codon”) encodes 1 amino acid What type of molecule does this? tRNA (transfer RNA) ~80 nte single stranded RNA molecule humans have ~500 genes that encode tRNA molecules an(codon 3’ -UCGGUAACUUGUACACC-! codon 5’ mRNA tRNA Molecules make the correlation between codon and amino acid: tRNA N-‐ -‐C N-‐ -‐C N-‐ -‐C ”reads” codon (triplet of nucleotides in mRNA) etc. mRNA: A-U-G - C-U-G -G-U-G-G-A-U-C-C-U-G-G-A-U-U-C Ribosome = Protein Factory amino acids are assembled according to order specified by mRNA and peptide bonds are formed last year’s Nobel Prize (Chem): studies that unveiled the structure &function of the ribosome: Venkatraman Ramakrishnan (UK), Tom Steitz (U.S.), Ada Yonath (Israel) Ribosome is enormous (complex of >80 proteins & 4 RNA molecules) Typical cell has millions of ribosomes! visible in electron micrograph: RIBOSOME enormous complex (~106 daltons) of protein + rRNA protein rRNA 25 nm 2/3 of ribosome is rRNA 23S rRNA from large ribosomal subunit: (schema(zed 2-‐D representa(on) 2900 nte Importance of Reading Frame gene(c code is NOT punctuated Note 3 possible reading frames for any given stretch of RNA only one gives desired protein How is reading frame chosen? How is reading frame maintained? thecatatethebug the cat ate the bug t hec ata tet heb ug th eca tat eth ebu g Reading Frame is established by first AUG codon ( = START) 5’-A-C-G-U-A-U-G-C-A-U-U-U-G-A-C-G-U-A-A-3’ Always end with a STOP codon that specifies NO amino acid RNA: 1) mRNA (messenger RNA) serves merely to carry informa(on 2) RNA with its own func(on: structural or cataly(c (ex. tRNAs, rRNAs) DNA DNA RNA pol I or RNA pol III RNA pol II mRNA (messenger) protein RNA (stuctural or cataly:c role) ex. snRNA rRNA tRNA

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