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Molecular Genetics PaCES Summer Program in Environmental Science Slide 2 What is Molecular Genetics? Slide 3 Molecular Genetics is is the field of biology that studies the structure and function of genes at a molecular level. Slide 4 Nucleotides pentose sugar phosphate nitrogenous base Slide 5 Pentose Sugars Slide 6 Nucleotides Bases Purines: two carbon rings Slide 7 Nucleotides Bases Pyrimidines: single carbon rings Slide 8 Polymerization of Nucleotides 5 carbon 3 carbon Slide 9 Polynucleotides (Nucleic Acids) 5 end 3 end Slide 10 The Double Helix Slide 11 Adenine (A) Thymine (T) Base Pairing in DNA Slide 12 Guanine (G) Cytosine (C) Base Pairing in DNA Slide 13 DNA Replication Slide 14 Strand Polarity in Complimentary Strands of Double-Stranded DNA Strand Polarity in DNA Slide 15 Adding Nucleotides Add to 3 end of new strand (begin at 5 of template) Slide 16 DNA Replication 3 end5 end 3 end 5 end parent DNA template RNA primer primase Slide 17 DNA Replication new complimentary DNA RNA primer 3 end5 end 3 end DNA polymerase III Slide 18 DNA Replication 3 end5 end 3 end newest DNA DNA polymerase I Slide 19 DNA Replication 3 end5 end 3 end parent DNA template new complimentary DNA Slide 20 Slide 21 PCR: Amplification of DNA Slide 22 Where's my DNA? Slide 23 DNA (genetic code) Polypeptide or Protein (linear sequence of amino acids) Gene Expression Slide 24 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 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 Slide 25 Proteins differ according to their order of amino acids TYR GLY SER ALA ILE MET LEU GLN GLY ASP ASN ILE GLN SER GLU HIS Protein 1 Protein 2 Slide 26 Steps of Gene Expression Transcription Translation Slide 27 Transcription Translation DNA mRNA protein Transcription and Translation Slide 28 Decoding DNA The first step of decoding the genetic message is to copy the nucleotide sequence from DNA to RNA Slide 29 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 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 Slide 30 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 Three types: Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA) Each plays a different role in the assembly of amino acids into protein Slide 31 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 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 Slide 32 rRNA Ribosomal RNA Remember, proteins are assembled ON ribosomes The rRNA is found attached to the ribosomes where the proteins are assembled Ribosomal RNA Remember, proteins are assembled ON ribosomes The rRNA is found attached to the ribosomes where the proteins are assembled Slide 33 Ribosome large subunit small subunit functional ribosome Slide 34 tRNA Transfer RNA A type of RNA that collects the necessary amino acids and escorts them to the assembly site on mRNA Transfer RNA A type of RNA that collects the necessary amino acids and escorts them to the assembly site on mRNA Slide 35 Structure of tRNA Slide 36 Gene Expression: Transcription Involves the copying of the genetic code into a molecule of messenger RNA (mRNA) Only copies the area of interest in DNA strand In the eukaryotic cell, transcription occurs in the nucleus. Prokaryotes dont have a nucleus. Base pairing rules apply except that uracil replaces thymine in RNA Involves the copying of the genetic code into a molecule of messenger RNA (mRNA) Only copies the area of interest in DNA strand In the eukaryotic cell, transcription occurs in the nucleus. Prokaryotes dont have a nucleus. Base pairing rules apply except that uracil replaces thymine in RNA Slide 37 RNA DNA RNA polymerase Location: In the Nucleus Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) All of Transcription (making mRNA) in eukaryotes takes places in the nucleus Slide 38 Only unwinds segment that codes for a certain protein RNA Polymerase add complementary bases Slide 39 Base Pairing in DNA Slide 40 Base Pairing in RNA Slide 41 The mRNA strand turns out the same as Sense Strand, except for Us instead of Ts Slide 42 Transcription Slide 43 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 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 Slide 44 Translation Slide 45 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) 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) Slide 46 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 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 Slide 47 Codon Chart Start Codon Slide 48 Codon Chart Slide 49 Amino Acid tRNA mRNA Ribosome Codon Anticodon Translation 53 Slide 50 Translation 53 Slide 51 Translation 53 Slide 52 Translation 53 Slide 53 Translation 53 Slide 54 Translation 53 Slide 55 Translation 53 Slide 56 Summary of Transcription and Translation Slide 57