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Molecular Genetics

Molecular Genetics. BWET Summer Program in Environmental Science. nitrogenous base. phosphate. pentose sugar. Nucleotides. Pentose Sugars. Nucleotides Bases. Purines: two carbon rings. Nucleotides Bases. Pyrimidines: single carbon rings. 3’ carbon. 5’ carbon.

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Molecular Genetics

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  1. Molecular Genetics BWET Summer Program in Environmental Science

  2. nitrogenous base phosphate pentose sugar Nucleotides

  3. Pentose Sugars

  4. Nucleotides Bases Purines: two carbon rings

  5. Nucleotides Bases Pyrimidines: single carbon rings

  6. 3’ carbon 5’ carbon Polymerization of Nucleotides

  7. 5’ end 3’ end Polynucleotides (Nucleic Acids)

  8. TheDouble Helix

  9. Thymine(T) Adenine (A) Base Pairing in DNA

  10. Guanine(G) Cytosine(C) Base Pairing in DNA

  11. DNA Replication

  12. DNA Replication

  13. DNA Replication Two new strands, each made of one template strand and one new strand.

  14. Strand Polarity in Complimentary Strands of Double-Stranded DNA

  15. Adding Nucleotides Add to 3’ end of new strand (begin at 5’ of template strand)

  16. RNA primer parent DNA template primase DNA Replication 5´ end 3´ end 3´ end 5´ end

  17. DNA polymerase III RNA primer 5´ end 3´ end 3´ end 5´ end new complimentary DNA DNA Replication

  18. newest DNA 5´ end 3´ end 3´ end 5´ end DNA polymerase I DNA Replication

  19. new complimentary DNA 5´ end 3´ end 3´ end 5´ end parent DNA template DNA Replication

  20. PCR: Amplification of DNA

  21. DNA (genetic code) Polypeptide or Protein (linear sequence of amino acids) Gene Expression

  22. Polypeptides and Proteins • Molecules composed of linear arrangements of amino acids • It is the sequence of these amino acids that determines the properties of a particular polypeptide or protein

  23. GLY SER ALA TYR ILE MET LEU GLN ASP ASN ILE GLN GLY SER GLU HIS Proteins differ according to their order of amino acids Protein 1 Protein 2

  24. Steps of Gene Expression Transcription Translation

  25. Transcription and Translation DNA Transcription mRNA protein Translation

  26. Decoding DNA • The first step of decoding the genetic message is to copy the nucleotide sequencefromDNAtoRNA

  27. RNA • Acts like a disposable copy of DNA for making protein • Controls the assembly of amino acids into protein • Same nucleotides as DNA • A single-strand of nucleotides • Contains URACIL instead of THYMINE

  28. Types of RNA • Three types: • Messenger RNA (mRNA) • Ribosomal RNA (rRNA) • Transfer RNA (tRNA) • Each plays a different role in the assembly of amino acids into protein

  29. mRNA • Messenger RNA • A direct copy of the DNA but using Uracil • Acts as a messenger from the DNA to the rest of the cell • base sequence reflects that of a gene that specifies the amino acid sequence of a protein

  30. rRNA • Ribosomal RNA • Remember, proteins are assembled ONribosomes • The rRNA is found attached to the ribosomes where the proteins are assembled

  31. Ribosome large subunit functional ribosome small subunit

  32. tRNA • Transfer RNA • A type of RNA that collects the necessary amino acids and escorts them to the assembly site on mRNA

  33. Structure of tRNA

  34. Gene Expression:Transcription - Involves the copying of the genetic code into a molecule of messenger RNA (mRNA) • Only copies the area of interest in the DNA strand • In the eukaryotic cell, transcription occurs in the nucleus. Prokaryotes don’t have a nucleus. • Base pairing rules apply except that uracil replaces thymine in RNA

  35. Location: In the Nucleus Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA All of Transcription (making mRNA) in eukaryotes takes places in the nucleus

  36. Only unwinds segment that codes for a certain protein RNA Polymerase add complementary bases

  37. Base Pairing in DNA

  38. Base Pairing in RNA

  39. The mRNA strand turns out the same as Sense Strand, except for U’s instead of T’s

  40. Transcription

  41. Gene Expression: Translation • Involves reading the triplet codons of the mRNA to determine the sequence of amino acids in a protein • Three stages: initiation, elongation, and termination • Occurs in the cytoplasm of all cells

  42. Translation

  43. The Nature of the Genetic Code • A sequence of three consecutive nucleotide bases codes for an amino acid in a protein • There are 64 possible combinations of a triplet code that draws from four different letters (bases)

  44. Codon • There are 20 different possible amino acids to make from different codons • 3 possible stop codon • 1 start codon • TAC on DNA • AUG on RNA

  45. Codon Chart Start Codon

  46. Codon Chart

  47. Amino Acid tRNA Ribosome Anticodon mRNA 5’ 3’ Codon Translation

  48. 5’ 3’ Translation

  49. 5’ 3’ Translation

  50. 5’ 3’ Translation

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