DNA & Translation

DNA and 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

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

The Genetic Code Codon: Combination of 3 mRNA nucleotides Each mRNA codon matches with 1 of 20 amino acids Ribosome reads codons 1 at a time Codon AUG = Methionine (Start) Codon GUU = Valine Codons UAA or UAG or UGA = Stop

Translation Overview Defined: Process of making proteins Step 1: mRNA enters ribosome Step 2: Ribosome reads one mRNA codon at a time (starting with the mRNA codon AUG) Step 3: tRNA delivers amino acids until a stop codon (one of 3) is reached = a completed protein.

Translation Details Translation begins when the mRNA codon “AUG” is read by the ribosome Each mRNA codon matches with a specific amino acid AUG = methionine GCU = alanine tRNA carries over the proper amino acid tRNA anticodon matches with the mRNA codon Ensures proper match One by one, amino acids are linked together Translation ends when a “stop” codon is read by the ribosome End result: Protein

Now the codon and anticodon match 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.

GAU AUG CCG AGU CCA GGA UCU UGA Questions to answer: List the amino acids that will be delivered to this ribosome. 2) What is the anticodon of each codon? 3) When finished, how many amino acids in size is this protein? Methionine Pro-line Serine Pro-line Gly-cine Serine STOP CODON Ribosome tRNA UAC tRNA GGC tRNA UCA tRNA GGU tRNA CCU tRNA AGA tRNA ACU GAU AUG CCG AGU CCA GGA UCU UGA

Always use mRNA to find the amino acid Practice Problem Always use mRNA to find the amino acid DNA mRNA codon tRNA anticodon Amino Acid Threonine T G A A C U U G A

Always use mRNA to find the amino acid Practice Problem Always use mRNA to find the amino acid DNA mRNA codon tRNA anticodon Amino Acid Lysine T T C A A G U U C

Always use mRNA to find the amino acid Practice Problem Always use mRNA to find the amino acid DNA mRNA codon tRNA anticodon Amino Acid C A G U C A glycine

REview Define transcription? Translation? Where does transcription take place? 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 # 9 -11