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RNA and Protein Synthesis

This article explores the process of protein synthesis, from the coding of the DNA message to protein formation, including transcription and translation. It covers topics such as genes, RNA types, codons, and the role of ribosomes in protein assembly.

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RNA and Protein Synthesis

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  1. RNA and Protein Synthesis

  2. DNA to RNA to Protein • Focus Questions: • How does the message coded in the base sequence of DNA eventually create a protein? • How does the code get out of the nucleus? • What happens at the ribosome that causes amino acids to eventually join to form a protein?

  3. One Gene One Protein • Genes: each gene is responsible for the production of a single protein (or part of a protein) • Human DNA contains over a 100,000 different genes • Proteins: determine the structure and function of an organism • Polypeptides of long chains of amino acids bonded together by peptide bonds • Ex: Enzymes, Structural proteins

  4. RNA RNA: • Sugar is ribose instead of deoxyribose • Has nitrogenous base URACIL instead of thymine (U instead of T) • Uracil also would pair with adenine (U-A) • Only single stranded

  5. 3 Types of RNA 1. Messenger RNA: (mRNA): • Copies genetic code from the DNA inside the nucleus (Transcription) • Leaves nucleus and goes to ribosome where is the message is read (Translation)

  6. 2. Ribosomal RNA: (rRNA) • Form the different parts of the ribosome 3. Transfer RNA: (tRNA) • Transfers different amino acids to the ribosomes where they are eventually assembled into protein chains • Each amino acid is coded for by a different triplet codon on mRNA • tRNA has an anticodon that will pair up with codon on mRNA

  7. Translation of Genetic Code at Ribosome 3 types of RNA work together

  8. How do Genes Code for Proteins? Transcription: (Information goes from DNA to mRNA) • Happens in nucleus • Enzymes unzip the portion of the DNA to be copied in the middle of the strand • A single stranded mRNA strand is created from the DNA template • Enzyme RNA polymerase helps this happen • mRNA leaves nucleus through pores and goes to ribosome • http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a2.html

  9. If the DNA template strand to be copied is • ATTGCATG • What would be the sequence of bases in the mRNA strand? • Remember it has U instead of T

  10. Triplet Codon: set of 3 nitrogenous bases on a mRNA strand • Each set of 3 can code for a different amino acid • There are 20 different amino acids

  11. There are 64 ways you can combine the four Nitrogenous bases in sets of 3 • AAA, GCC, ATA, ATC, GTA etc. • Sometimes more than one codon can code for the same amino acid • Ex: AAA and AAG both code for phenylalanine • 3 codons signal protein synthesis to stop • 1 codon signals protein synthesis to start (AUG)

  12. Translation: (from mRNA to protein) • Occurs at ribosomes • Process of converting information coded in mRNA into sequence of amino acids • Involves transfer RNA • Bring specific amino acids to ribosomes so they can be assembled into proteins • Has “anticodon” that matches up with each triplet codon on mRNA • Bottom of tRNA has anticodon triplet

  13. Translation Process: • 1st triplet codon of mRNa attaches to ribosome • tRNA carrying amino acid pairs with mRNA codon • Usually mRNA at start is AUG (“start codon”) • mRNA slides along ribosome to next codon • New tRNA with amino acid pairs to mRNA codon • Amino acids get joined by enzyme by a peptide bond • Process continues and chain of amino acids form until a stop codon on mRNA is reached • Protein detached from ribosome

  14. Transcription Video: (really good watch this!!) • http://www.hhmi.org/biointeractive/media/DNAi_transcription_vo1-lg.mov Translation Video: (really good watch this!!) • http://www.hhmi.org/biointeractive/media/DNAi_translation_vo1-lg.mov Transcription and Translation Activity: • Game where you make a Protein • http://learn.genetics.utah.edu/content/begin/dna/transcribe/

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