BIO 101 1st EditionLecture 21Outline of Last LectureI. DNA as the genetic materiala. Transformation Experimentsb. Bacteriophage experimentsII. DNA StructureIII. DNA ReplicationOutline of Current LectureI. TranscriptionII. Translationa. Initiationb. Elongationc. TerminationIII. Genetic Codea. Messenger RNAb. Transfer RNAc. RibsosomeIV. Mutationsa. Base pair substitutionsb. Base pair deletions or insertionsV. Split Genes and RNA ProcessingVI. MicroRNAs and Gene ExpressionVII. Molecular Biology of CancerChapter 17- From Gene to Protein- Inherited DNA controls the cell’s activities- How? It has the code for how to make enzymes and other proteins- DNA does not make protein directly- First, the information in DNA is copied to an RNA molecule called messenger RNA (mRNA)- The mRNA programs the making of protein- This protein is called the “CENTRAL DOGMA OF MOLECULAR BIOLOGY”Transcription- synthesis of RNA from a DNA template- Information in DNA is copied into a RNA molecule- mRNA is made by an enzyme called RNA polymeraseBIO 101 1st Edition- RNA polymerase binds to DNA at the beginning of a GENE (gene has the code for how to make some particular protein) at a specific place called the promoter- RNA polymerase is guided the promoter by special proteins called TRANSCRIPTION FACTORS- Once at the promoter, RNA polymerase moves along the DNA and separates the two strands- One of the two strands acts as a template to make RNA (by the base pairing rules)- RNA nucleotides (C, G, A, U) line up properly on the DNA template strand (remember that RNA nucleotides include U in place of T) by hydrogen bonding- RNA polymerase links the lined up RNA nucleotides together to form the RNAmolecule- RNA is made ~60 nucleotides/second- As RNA is made, it peels off of the DNA- Then 2 DNA strands come back together- TRANSCRIPTION stops at a place on the DNA called a terminator- At the terminator, RNA polymerase releases the finished mRNA molecule and then falls off the DNATranslation- synthesis of protein using mRNA informationmRNA- polymer of 4 different nucleotides (G, C, U, A)proteins- polymers of 20 different amino acidsThe Genetic CodeHow does the code work to translate from the language of nucleotides to the language of amino acids?X 1 nucleotide 1 amino acid (could only code for 4 amino acids)X 2 nucleotides 1 amino acids, # of combinations of 4 things taken 2 at a time, 4^2= 16 (could only specify 16 different amino acids)BIO 101 1st Edition3 nucleotides 1 amino acid, 4^3= 64 possible combinations, more than enough!Each 3 nucleotide code word is called a CODON- codes for some particular amino acidFirst Codon was deciphered in 1961 by Nirenberg:- He made a synthetic mRNA (test tube)- poly U- Then translated it into vitro (in test tube)- The protein that was made was composed entirely of the amino acid phenylalanine - Therefore, the codon UUU code for the amino acid phenylalanine- Later all 64 possible combinations of nucleotides were decipheredo 61- code for amino acidso 3- don’t code for any amino acid. Instead they are signals to STOP translation, STOP CODONS- All living organism share the same genetic code- Indicates that the genetic code was established very early in evolution- this is an example of the unity in lifeHow does the cell translate nucleotide codon into proteins?Equipment needed for translation: - mRNA (messenger RNA)- tRNA (transfer RNA)- ribosomes1. Messenger RNA (mRNA)- RNA molecule that carries the coding information, a series of codons that must be decoded, one right after the otherTranslation starts at the first START CODON (AUG) from the 5’ end of the molecule- The region from the CAP (a stabilizing and regulating structure) to theSTART CODON is not translated into amino acids- it is called the 5’ untranslated region (5’UTR)- Translation ends at a STOP CODON, not at the very end of the mRNA- The region between the STOP CODON and the 3’ end is NOT TRANSLATED and is called the 3’ untranslated region (3’UTR)- The 3’ end of the mRNA has a string of As- called polyAtail- acts to stabilized mRNA and regulate translation2. Transfer RNA (tRNA)- function as a “decoder” pairs the right amino acid with its CODON (i.e. amino acids do not recognize their own codons.BIO 101 1st EditiontRNA is a small RNA (~80 nucleotides)- shaped like an L (upside down and backwards L)- One end has a sequence of 3 nucleotides called the ANTI-CODON- it recognizes a particular codon on the mRNA (by the base pairing rules)- The other end of the tRNA carries the correct amino acid- (the amino acid coded for by the codon that is recognized by the anti-codon of thetRNA)3. Ribosome- organelle that coordinates the pairing of tRNAs with their mRNA codons- Ribosomes are composed of 2 subunits LARGE SUBUNIT and SMALL SUBUNIT- The 2 ribosomal subunits are separate EXCEPT when translating mRNA into protein - Each ribosome has one binding site for mRNA and 3 binding sites for tRNAs (E site, P site and A site)Translation= synthesis of proteins using info in mRNA - Occurs in 3 stages: initiation, elongation, termination- First 2 stages require energy input from cell, all stages require enzymes1. Initiation- mRNA and special tRNA (initiator tRNA) bind to small subunit of ribosome- Requires a set of initiation factors- Initiator tRNA anticodon is base paired with the START CODON on mRNA- Large subunit of ribosome binds with initiator tRNA is the P site  functioning ribosome2. Elongation - A tRNA with correct anticodon for the next codon (after the START CODON) binds in the A site (with its anticodon base pairing with next codon)- A peptide bond forms between the 2 amino acids on the tRNAs in the P and A sites- The connected amino acids stayed attached to tRNA in A site, but are released from tRNA in P site.BIO 101 1st Edition- The ribosome moves over ONE CODON- so that tRNA in P site (now without an amino acid) is in E site (and is released), the tRNA that wasin A site is now in P site (still holding the growing amino acid chain) and the A-site is over next codon- Cycle is repeated until protein is complete (ribosome always moving ONE CODON at a time from 5’ 3’3. Termination- translation stops- Ribosome comes to a termination codon- it does not code for any amino acid, so no tRNA pairs with it- A release factor binds in A site- this releases the protein, ribosome separates into