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DNA & Translation. Gene : section of DNA that creates a specific protein Approx 25,000 human genes Proteins are used to build cells and tissue Protein synthesis involves two processes: 1) Transcription 2) Translation. DNA and Translation. Transcription Review.
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DNA & Translation
Gene: section of DNA that creates a specific protein Approx 25,000 human genes Proteins are used to build cells and tissue Protein synthesis involves two processes: 1) Transcription 2) Translation DNA and Translation
Transcription Review • Transcription takes place in the nucleus • 1) DNA double helix is broken apart • 2) mRNA nucleotides match up • 3) Finished mRNA detaches, and moves to a ribosome
Codon: Combination of 3 mRNA nucleotides Each mRNA codon matches with 1 of 20 amino acids Ribosome reads codons 1 at a time AUG codon: Activates the ribosome (start codon) UAA or UAG or UGA codon: deactivates the ribosome (stop codon) The Genetic Code
Translation Overview • Defined: Process of making proteins • Step 1: mRNA enters ribosome • Step 2: Ribosome reads one mRNA codon at a time • Step 3: tRNA delivers amino acids until a protein is created
Translation begins when the mRNA codon “AUG” is read by a ribosome Ribosome reads one codon at a time AUG = methionine GCU = alanine tRNA carries over the proper amino acid tRNA anticodon matches with the mRNA codon Prevents delivery of wrong amino acid One by one, amino acids are linked together Translation ends when a “stop” codon is reached What just happened?: A ribosome made a protein Translation Details
Now the codon and anticodon match. This ensures the proper amino acid (serine) is delivered. This is why the anticodon is important! Because the codon and anticodon don’t match, the wrong amino acid will not be delivered.
Questions to answer: • In order, list the amino acids that will be delivered to this ribosome. • What is the anticodon of each codon? • When finished, how many amino acids in size is this protein? tRNA UAC tRNA GGC tRNA UCA tRNA GGU tRNA CCU tRNA AGA Six Methionine (MET) Proline (PRO) Serine (SER) Proline (PRO) Glycine (GLY) Serine (SER) Ribosome tRNA UAC tRNA GGC tRNA UCA tRNA GGU tRNA CCU tRNA AGA ignore GAU AUG CCG AGU CCA GGA UCU UGA start stop
Always use mRNA to find the amino acid Practice Problem Threonine T G A A C U U G A
Practice Problem Always use mRNA to find the amino acid Lysine T T C A A G U U C
Always use mRNA to find the amino acid Practice Problem C C A G G U C C A glycine
Review • Define transcription? Translation? • What are genes and how are they different from chromosomes? • How many nucleotides make a codon? • The anticodon can be found on which object? • The anticodon must match the ______. • Place the following steps in order from start to finish: a. Proteins are assembled b. Ribosome reads a codon one at a time c. mRNA arrives at the ribosome d. tRNA delivers amino acids to the ribosome 7) Be able to solve practice problems similar to the three examples on slides #8-11.