Lesson 6

• Archibald Garrod is and English physician who related gene and enzyme
• Garrod studied Alkaptonuria
• Alkaptonuria is when urine turns black when exposed to air
• George Beadle and Edward Tatum discovered one gene one enzyme hypothesis
• An enzyme catalyzes a step in a metabolic reaction
• One gene one protein:

  Not all proteins are enzymes. They are gene products
• Gene contains info for making one RNA
• Promoter is a DNA sequence which transcription enzyme binds
• RNA polymerase is the MAIN enzyme for transcription
• One gene one polypeptide

  • Hemoglobin has 2 alpha and beta chains
• Enzymes catalyze metabolic reactions
• Gene contains information for 1 RNA and polypeptide
• Promoter is a DNA sequence which transcription enzyme binds
• RNA polymerase is the main enzyme for transription
• Prokaryotic transcription has 10 seq of TATAAT and 35 seq of TTGACA
• Products of transcription: RNA Types

  Messenger RNA (mRNA) carries the message
• Products of transcription: RNA Types

  transfer RNA (tRNA) brins amino acids to synthesis site
• Products of transcription: RNA Types

  ribosomal RNA (rRNA) is major component of ribosomes
• In prokaryotic ribosome: 70S

  30S (Svedberg value) with 16 S rRNA and 21 ribosomal proteins
• In prokaryotic ribosome: 70S

  50 S with 23 S rRNA , 5 S rRNA, 31 ribosomal proteins
• In eukaryotic ribosome: 80 S

  mammalian has 40S with 18S rRNA + 30-35 proteins
• In eukaryotic ribosome: 80 S

  60S with 5.8S rRNA + 28S + 5S rRNA + 40-45r proteins
• In eukaryotic transcription, promoters have 25-30 TATA box or Goldberg-Hogness Box and 75-80 CAAT box
• Codon is a 3 base sequence in mRNA
• Anticodon is a 3 base sequence in a tRNA
• Genetic code is a set of 64 codons
• Polypeptide is a single protein chain
• Formula for Translation:

  mRNA + Ribosomes + tRNAs with aa
• George Gamow proposed genetic coding system
• Marianne Grunberg-Manago and Severo Ochoa made synthetic RNAs using polynucleotide phosphorylase
• Marshall Nirenberg and Johann Heinrich Matthaei produced artificial mRNA and cell free system
• poly U (UUU) = polyphenylalanine
• Poly C (CCC) = proline
• Har Gobind Khorana constructed different repeating nucleotide combinations (UCU, CUC)
• Characteristic of genetic code:

  • triplet code
  • continuous
  • non overlapping
  • universal
  • degenerate
  • start and stop signals
  • wobble in anticodon
  • unambigous
• Yanofsky = linear correspondence in DNA seq and amino acids
• Genomics refers to molecular analysis of entire genome of species
• Genomics is possible due to rapid development of genetic technology
• 2 types of genomics

  • structural
  • functional
• structural genomics is the direct analysis of DNA itself