The Genetic Code and Its Translation

1
Chapter 15

• The Genetic Code and Its Translation

2
Beadle-Tatum Experiment

• Worked with Neurospora
• Can make or its self all the amino acids needed
• Xrayed the spores to increase the mutation rate
• Found that different mutations relulted in the
  loss of ability to synthisize different amino
  acids.

3
(No Transcript)
4
(No Transcript)
5
One gene- one protein One gene- one polypeptide
6
Structure of HemoglobinLinus Pauling

• He used electrophoresis to separate and measure
  hemoglobin.
• Found that people with sickle-cell have a
  different protein (hemoglobin).

7
From DNA to Protein

• How is the specific language of DNA converted
  into the specific language of Protein?
• RNA
• Evidence
• RNA is found mostly in cytoplasm
• Cells making large amounts of protein have
  numerous ribosomes (ribosomes are 2/3 RNA)
• When a cell is infected by a virus before viral
  protein is made viral RNA is sythesized

8
Central Dogma
9
The Genetic Code

• George Gamow (big bang guy)
• Figured that is you have 20 amino acids and only
  4 nucleotides than each amino acid must be coded
  for by 3 nucleotides
• 41 4
• 42 16
• 43 64

10
Breaking the CodeNirenberg Matthaei

• Put random RNA in E. coli and observed that they
  made protein
• Then put synthetic poly-U in and observed that
  the E. coli made phenylalanines
• Put synthetic RNA in for the 64 possible triplets
  and discovered that
• 61 code for amino acids (genetic code is
  degenerate)
• 3 are termination codons
• UGA, UAG, UAA

11
(No Transcript)
12
(No Transcript)
13
RNA as Messenger

• Copying DNA to RNA
• Transcription
• Occur is the 5-3 direction
• Catlyzed by RNA polymerase
• Occurs on the sense strand
• Promotors
• Terminator
• Long 500?10,000 nucleotides

14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
Translation
19
RNA

• 3 types
• mRNA
• rRNA (most abundant)
• tRNA

20
rRNA

• Makes up 2/3 of the ribosomes
• Ribosomes are made of two subunits
• 30S has binding site for mRNA
• 50S has two binding sites for tRNA
• Total sedimentary value is 70S (in prokaryotes)

21
(No Transcript)
22
tRNA
Binds tRNA to surface of the ribosome.
23
Linking amino acids to tRNA

• ATP molecule is cleaved
• Two phosphates released, energy is supplied
• Amino acid-AMP-enzyme complex is formed
• Amino acid-AMP-enzyme complex meets with tRNA
  molecule
• AMP molecule is released from enzyme
• Bond is formed between amino acid and 3 end of
  tRNA molecule
• Amino acid-tRNA complex is released
• tRNA molecule hydrogen bonds to mRNA
  (anticodon-codon)
• Peptide bonds form between amino acids
• H-bonds break and tRNA is recycled to pick up
  more AA

24
(No Transcript)
25
(No Transcript)
26
Transcription
27
(No Transcript)
28
(No Transcript)
29
(No Transcript)
30
Formation of the Initiation Complex during
Translation
31
Joining of the 50S Ribosomal Subunit to the
Initiation Complex during Translation
32
Protein Elongation during Translation
33
Termination of Translation
34
Summary of Tranlation
35
Mutations
36
Definition

• Change in the sequence or number of nucleotides
  in the nucleic acid of a cell
• Point mutation
• Frame-shift mutation

37
Universality of Genetic code

• It is
• Exception mitochondria