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RNA and Protein Synthesis

RNA and Protein Synthesis. 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?.

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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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