TRANSLATION/PROTEIN SYNTHESIS Unit 4 – Part 1

Central Dogma DNA mRNA Proteins Traits

DNA vs. RNA Review  DNA  Double stranded  Made up of repeating units called nucleotides  Contains the 5 C (pentose) sugar Deoxyribose  Found in the nucleus  4 nitrogen bases  Adenine, Guanine, Cytosine, Thymine  RNA  Single Stranded  Made up of repeating units called nucleotides  Contains the 5 C sugar ribose.  Found in the nucleus & cytoplasm  4 nitrogen bases  Adenine, Guanine, Cytosine, uracil  3 forms  mRNA, rRNA, tRNA Deoxyribonucleic acidRibonucleic acid

Transcription Review DNA  mRNA  DNA makes proteins, which control all of our traits, but DNA cannot leave the nucleus.  Therefore it has to find a way to get it’s message from the nucleus to the cytoplasm where the protein factories are (ribosomes).

Transcription Review cntd.  The enzyme RNA polymerase attaches to a strand of DNA and begins to unwind and unzip the strand. It also adds the RNA nucleotides to the undone DNA strand one at a time making a mRNA strand.

Transcription Review cntd.  Eventually RNA polymerase will reach a spot on the DNA that signals it to stop making the mRNA strand.  After it reaches this point it can let go and leave the nucleus.  From the nucleus it goes into the cytoplasm and attaches to a ribosome.

Translation/Protein Synthesis  Step where the mRNA code is translated into an amino acid sequence: MRNA to protein  A series of amino acids  Also called protein synthesis because this is the step where proteins are made.

Translation/Protein Synthesis

 RNA is read 3 nitrogen bases at a time  Each triplet of bases is called a codon  Each 3 letter codon is a code for an amino acid  A series of 50-5,000 amino acids make up a protein.

Translation/Protein Synthesis Steps 1. Once the mRNA sequence leave the nucleus it attaches to the ribosome 2. The ribosome (which is partly made up of an rRNA molecule) travels down the mRNA sequence until it finds a start spot called a start codon  AUG: the ONLY start codon 3. The start codon is the spot where the amino acids start to make proteins.

Translation/Protein Synthesis Steps 4. After the ribosome finds the start codon a transfer RNA molecule (tRNA) attaches to the codon by an anti-codon and carries an amino acid.  Each tRNA anticodon carries only ONE amino acid. 5. Amino acids are deposited until it reaches one of 3 stop codons.  UAA, UAG, UGA 6. After a stop codon is reached, the amino acid chain is let go and a protein is formed.

Translation/Protein Synthesis Steps

Translation/Protein Synthesis  How does the tRNA molecule know what amino acid to drop off?  Each codon(mRNA) matches a specific anticodon (tRNA). Each anticodon matches a specific amino acid.  Codon Chart:  To determine what amino acid matches which codon refer to the codon chart.