1 PROTEIN SYNTHESIS

From Gene to Protein From DNA to RNA and from RNA to Proteins Our bodies use our genetic code to make proteins.

DNA DNA contains genes, sequences of nucleotide bases These Genes code for polypeptides (proteins)

4 Genes & Proteins  Proteins are used to build cells and do much of the work inside cells A protein is one or more polypeptide. Polypeptides are chains of amino acids linked together by peptide bonds

A polypeptide chain can be made of up to 20 amino acids The shape of the polypeptide is determined by which amino acids are present and in what order 20 different amino acids exist An amino acid is determined by the codon. 5

If you were going to build a machine to read the genetic code, how would it read? Would one letter = one word? Our genetic code is read in codons Each codon represents one amino acid Some codons tell the ribosome to start or stop translation 6

7 A codon is three nucleotide bases that represent a ‘word’ 1 codon = 1 amino acid (1 st block) Amino acid chain Polypeptide (1+) Protein

Gene to RNA to Protein The first step in decoding these instructions is to copy part of DNA into RNA RNA uses this copy to make proteins 8

Transcription (second block) DNA -> RNA, Happens in the nucleus STEPS: 1. RNA polymerase opens (unwinds) a section of DNA 2. RNA polymerase uses DNA as a template 3. RNA molecules are produced that are complementary to the DNA base pairs. 9

Differences (3 rd block) DNA Sugar is Deoxyribose Double stranded AT / CG (nucleotide bases) The masterplan RNA Sugar is Ribose Single stranded (usually) AU / CG (nucleotide bases) A BLUEPRINT of the masterplan 10

Functions of RNA disposable copy of DNA working copy of a single gene has many jobs, mostly makes protein controls how amino acids are made into proteins 11

types Three main types of RNA (4 th block) Messenger RNA (mRNA)- carry copies of information to ribosomes Ribosomal RNA (rRNA)- located on ribosomes Transfer RNA (tRNA)- carries amino acids to ribosomes 12

Recap of Transcription When making a protein, the cell transcribes DNA into _______? This takes place in the _______? Now What? Time to move to the cytoplasm and synthesize a protein! 13

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Amino Acid tRNA Anti-Codon 15 Each tRNA molecule carries just one kind of amino acid and the anticodon— three base pairs which are complementary to one mRNA codon 1 st box: draw one tRNA and label

Translation 1. ribosome attaches to an mRNA molecule in the cytoplasm. 2. As the ribosome reads each codon and guides the matching anti- codon into place 16 2 nd box

Translation 3. a second anti- codon molecule binds 4. A peptide bond forms between the amino acids. (At the same time, the bond holding the first tRNA molecule to its amino acid is broken.) tRNA is released rd box

Translation The ribosome continues to move along the mRNA, forming the peptide bonds until it reaches the ‘stop’ codon The ribosome then releases the mRNA and the polypeptide 18 4 th box

Sum up Translation 19

Who cares about this? How are we going to use this information? –This is how every part of your body is formed, this is happening hundreds of times per day in your body! We will use this to transcribe and translate pieces of DNA… 20

Complimentary DNA What would the complimentary DNA strand be? CTACAT 21 GATGTA

Transcribe What would the mRNA codons be? GATGTA 22 CUACAU

Translation What would the tRNA anti-codon be? CUACAU 23 GAUGUA

24 What amino acid would these code for? GAU

25 GUA

Protein synthesis 1. mRNA transcribed from DNA 2. mRNA exits through nuclear pore to cytoplasm/ribosome 3. Loaded tRNA bonds mRNA at ribosome 4. Polypeptide chain grows in response to mRNA codons 5. Completed protein either used by cell or packaged and exported Candy Factory 1. Boss gives recipe to messenger 2. Messenger leaves office, goes to factory workstations 3. Workers pick up ingredients at workstation 4. Ingredients are combined according to recipe 5. Candy assembly finished; workers eat some, rest is wrapped for shipment 26