From Gene to Protein Central Dogma of Biology: DNA  RNA  Protein http://nobel.scas.bcit.ca/resource/dna/station2.htm# http://www.metacafe.com/watch/530045/the_process_of_protein_synthesis_with_mr_gibbons/

Scientists that worked on Protein Synthesis: Archibald Garrod: pioneered the field of inborn errors of metabolism. First proposed the relationship between genes and proteins. George Beadle and Edward Tatum: worked with bread mold Neurospora Crassa 1gene1protein hypothesis changed to 1gene1polypeptide some proteins are made from more than one gene

Protein Synthesis: overview Transcription: synthesis of RNA (mRNA) under the direction of DNA Translation: actual synthesis of a polypeptide under the direction of mRNA http://www.studiodaily.com/main/technique/tprojects/6850.html

Compare RNA to DNA: RNA: Ribose 5 C sugar Uracil instead of Thyamine single stranded More reactive 3 kinds m-RNA t-RNA r-RNA DNA: Deoxyribose 5 C sugar Thyamine double stranded helix More stable

Ribosomal (r- RNA): Is the ribosome Site of protein synthesis Transcribed in the nucleolus 2 sub-units: smaller 40s sub-unit larger 60s sub-unit

Messenger (m-RNA): Physical link between the gene and the protein DNA is too large to leave the nucleus This is what gets translated m-RNA structure: 5' leader- aids in ribosome binding Coding region- translates into polypeptide 3' trailer http://www.metacafe.com/watch/88468/750_pound_man/

Transfer (t-RNA): Responsible for deseifering the codons Brings the amino acids together according to sequence on m-RNA t-RNA structure: 90 nucleotides that pair up causing folding to give its shape anticodon loop- pairs with the codon of m-RNA

The Problem: How can 4 bases, or combinations there of, code for the 20 different amino acids? How does the info get from the DNA to the final protein product? DNA only has 4 variable parts, the 4 different bases. 1. If 1 base coded for 1 amino acid = 41 (4) 2. If 2 bases coded for 1 amino acid = 42 (16) 3. If 3 bases coded for 1 amino acid = 43 ( 64) 20 different amino acids used to make proteins

The Triplet Code Each coding part of DNA (codon) consists of 3 adjacent nucleotides that specify for one of 20 amino acids. GUU (valine), CUA (leucine), CGU (argenine) ‘U’ (uracil) replaces ‘T’ in RNA Synonymous codons- are different codons that specify for the same amino acid Start signal- AUG (methionine) Stop signal- UAA, UAG, UGA

Transcription, I RNA polymerase: Promoter region on DNA: compliments RNA nucleotides from the DNA code Promoter region on DNA: where RNA polymerase attaches site of initiation Terminator region: signals the end of transcription Transcription unit: stretch of DNA transcribed into RNA http://hybridmedicalanimation.com/anim_ppar_qtVideo.html

Transcription, II Initiation~ Elongation~ Termination~ transcription factors mediate the binding of RNA polymerase to an initiation sequence Elongation~ RNA polymerase continues adding nucleotides Termination~ RNA polymerase detaches http://bcs.whfreeman.com/thelifewire/content/chp12/1202001.html

mRNA modification Capping- methylated cap added to 5' end, aids in binding to ribosome Poly A-tail- 50-150 adenines added to 3' tail, helps transport m-RNA out of the nucleus Introns- regions that don’t code for protein Removed by Splicesome to form mature m-RNA (splicing) Exons- region that expresses protein Prokaryotic m-RNA have no methylated cap, poly a-tail, or introns ready to go as soon as m-RNA is made http://www.dnatube.com/view_video.php?viewkey=140704575d499c997b6c&tags=cell&sort=title

Translation, I mRNA from nucleus is ‘read’ along its codons by tRNA’s anticodons at the ribosome tRNA has a specific anticodon and amino acid attached http://bcs.whfreeman.com/thelifewire/content/chp12/1202003.html

Translation, II rRNA site of mRNA codon & tRNA anticodon coupling P site holds the tRNA carrying the growing polypeptide chain A site holds the tRNA carrying the next amino acid to be added to the chain E site discharged tRNA’s http://www.johnkyrk.com/DNAtranslation.html

Translation, III Initiation~ union of mRNA, tRNA, small ribosomal subunit, followed by large subunit Elongation~ •codon recognition •peptide bond formation •translocation Termination~ ‘stop’ codon reaches ‘A’ site Polyribosomes: translation of mRNA by many ribosomes http://hybridmedicalanimation.com/demoReel.html http://learn.genetics.utah.edu/units/basics/transcribe/

Mutations: genetic material changes in a cell Point mutations Changes in 1 or a few base pairs in a single gene Mutagens: physical and chemical agents that change DNA Types of mutations: Substitutions Insertions or deletions Inversion

Base-pair substitutions: Replacement of one nucleotide with another silent mutations no effect on protein missense to a different amino acid (different protein) nonsense to a stop codon and a nonfunctional protein

Base-pair insertions or deletions: Additions or losses of nucleotide pairs Frameshift mutation - alters the ‘reading frame’ of triplets

Inversion: An entire section of DNA is reversed. Example: May involve only a few bases or large regions of a chromosome containing several genes. Example: Original: The fat cat ate the wee rat. Inversion: The fat tar eew eht eta tac.