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 AUG codon: Activates the ribosome (start codon) UAA or UAG or UGA codon: deactivates the ribosome (stop codon)

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 Details 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

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.

Six GAU AUG CCG AGU CCA GGA UCU UGA UAC GGC UCA GGU CCU AGA Ribosome 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

Threonine T G A A C U U G A DNA mRNA codon tRNA anticodon 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

Lysine T T C A A G U U C DNA mRNA codon tRNA anticodon 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

C A G U C A glycine DNA mRNA codon tRNA anticodon 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? 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.

mRNA codes

mRNA codes