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Rna

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Rna

  1. 1. RNA
  2. 2. <ul><li>Differences between RNA and DNA ? </li></ul>
  3. 3. RNA vs DNA <ul><li>Strand. </li></ul><ul><li>Pentose sugar. </li></ul><ul><li>Base pair. </li></ul><ul><li>Fx. </li></ul>
  4. 4. RNA properties: <ul><ul><li>RNA = nucleotide bases + 5 carbon sugar (ribose instead of deoxyribose) + phosphate </li></ul></ul><ul><ul><li>RNA has 4 types of nucleotide bases: A, C, G, U (U replaces T) </li></ul></ul><ul><ul><li>RNA is usually a single strand, not a helix </li></ul></ul>
  5. 5. RNA <ul><ul><li>nucleotide bases + 5 carbon sugar (ribose instead of deoxyribose) + phosphate </li></ul></ul><ul><ul><li>RNA has 4 types of nucleotide bases: A, C, G, U (U replaces T) </li></ul></ul><ul><ul><li>RNA is usually a single strand, not a helix </li></ul></ul>
  6. 6. Types of RNA <ul><li>  Messenger RNA ( m-RNA ) = An RNA copy of a gene  </li></ul><ul><li>Transfer RNA ( t-RNA ) Transfer amino acids to ribosome; have anticodons which match the m-RNA codons. </li></ul><ul><li>Ribosomal RNA ( r-RNA ) Ribosomal structure; also includes the enzyme peptidyl transferase (makes peptide bonds) </li></ul>
  7. 7. <ul><ul><li>The transcribed code is carried from the nucleus to the ribosomes by messenger RNA (m-RNA) </li></ul></ul><ul><ul><li>The ribosomes contain ribosomal RNA (r-RNA). This type is structural and also acts as an enzyme when the protein is lengthened </li></ul></ul><ul><ul><li>Transfer RNA (t-RNA) carries amino acids to the ribosomes: there must be at least 20 types of t-RNA </li></ul></ul>
  8. 8. Types and Fx of RNA <ul><li>mRNA </li></ul><ul><li>Formed in the nucleus. </li></ul><ul><li>Made from DNA template. </li></ul><ul><li>Fx: Carries gen code from DNA -cytoplasm – ribosomes on the ER. </li></ul>
  9. 9. Structure of mRNA <ul><li>the longest of the RNA molecules </li></ul><ul><li>Before entering the cytoplasm on its way to the ribosomes, an mRNA molecule is modified. </li></ul><ul><li>A 7-methylguanosine &quot;head&quot; is added which serves to help attach the mRNA to a ribosome during protein synthesis. </li></ul><ul><li>A poly-A &quot;tail&quot; ( 200 adenosine residues) is attached to the end of the mRNA molecule to prevent it getting destroyed by enzymes in the cytoplasm. </li></ul>
  10. 10. tRNA <ul><li>molecule which transfers the amino acid to the ribosome. </li></ul><ul><li>There are at least 20 kinds of t-RNA because there are 20 different amino acids </li></ul><ul><li>Fx: Bonds to a2, transports them to ribosomes for assembly into polypeptides. I t is used in the synthesis of proteins </li></ul>
  11. 11. Structure of tRNA <ul><li>On one end of the tRNA molecule is an area to which a specific amino acid attaches </li></ul><ul><li>On the other end is a sequence of three base pairs called the anticodon, the complement of the codon on the mRNA which codes for a certain protein. </li></ul><ul><li>mRNA binds to a ribosome where the codons are left exposed. </li></ul><ul><li>These codons needs to be recognised by anticodons on tRNA . </li></ul><ul><li>Amino acids attach to the new protein only if the t-RNA anticodon matches (is complementary to) the m-RNA codon </li></ul>
  12. 12. tRNA
  13. 13. rRNA <ul><li>Component of ribosomes </li></ul><ul><li>Place where polypeptide chains are built up. </li></ul><ul><li>Enzyme peptidyl transferase makes peptide bonds. </li></ul>
  14. 14. <ul><li>Ribosome finds start codon (AUG), then decodes the message, 3 bases at a time </li></ul><ul><li>When the ribosome reaches the stop codon the protein is released and the decoding can start over to make another protein </li></ul>
  15. 15. Summary Transfer amino acids to ribosome have anticodons which match the m-RNA codons. At least 20 types required- one for each amino acid.   t-RNA   Transfer RNA   Ribosomal structure; enzyme peptidyl transferase (makes peptide bonds)   r-RNA   Ribosomal RNA   An RNA copy of a gene   m-RNA   Messenger RNA

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