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REPLICATION. DNA. DNA. TRANSCRIPTION. mRNA. TRANSLATION. amino acids. protein !. Transmission of Information. SUMMARY. http://www.youtube.com/watch?v=NJxobgkPEAo http://www.youtube.com/watch?v=D5vH4Q_tAkY http://www.youtube.com/watch?v=d1UPf7lXeO8

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Presentation Transcript
Transmission of information

REPLICATION

DNA

DNA

TRANSCRIPTION

mRNA

TRANSLATION

amino acids

protein !

Transmission of Information

  • SUMMARY


Transmission of information

  • http://www.youtube.com/watch?v=NJxobgkPEAo

  • http://www.youtube.com/watch?v=D5vH4Q_tAkY

  • http://www.youtube.com/watch?v=d1UPf7lXeO8

  • http://www.youtube.com/watch?v=B6O6uRb1D38

  • http://www.youtube.com/watch?v=yJdAxuIA6QM

  • http://www.youtube.com/watch?v=u9dhO0iCLww


Transcription
Transcription

  • Copies the DNA code to mRNA

    • DNA unwinds

    • Only 1 strand is transcribed

    • Complimentary base pairing of nucleotides

      C-G G-C T-A A-U

    • This pairing forms the mRNA

    • RNA polymerase helps form the new mRNA

      • initiation signal - “start here”

      • termination sequence - “stop synthesis”


Transcription1
Transcription

Termination

sequence

mRNA 3’

mRNA 5’


Translation
Translation

  • Translation occurs on the ribosomes

    • Ribosome spheres dissociate into 2 parts

    • Each “half” of ribosome is made of...

      • rRNA

      • polypetides (enzymes)

    • 60S unit (larger piece of ribosome)

    • 40S unit (smaller piece of ribosome)


Translation1
Translation

  • Translation occurs on the ribosomes

    • mRNA is “stretched out” on ribosome

    • Nucleotides on the mRNA are grouped into 3s to form: “CODONS”

      • each CODON carries a 3 letter code to translate into an amino acid

      • “Anticodons” on tRNA will match-up with the codons


Ribosome

60 S

mRNA

codons

UUG

AUG

GCU

AUG

3’

5’

Ribosome

rRNA

rRNA

40 S

AUG – School Starts in August


Genetic code
Genetic Code

  • The Genetic Code

    • Broken in 1961 by Marshall Nirenberg and coworkers

    • Made poly-U mRNA and “fed” it to ribosomes

    • The only peptide made was phenylalanine

    • Therefore, UUU codes for Phe

    • Each AA is coded for by a sequence of 3 nucleotides on mRNA = CODON


Translation2
Translation

  • 4 STAGES in Protein Synthesis:

    • Activation

    • Initiation

    • Elongation

    • Termination


Activation

activated AA

fMET

anticodon

C

A

G

Activation

  • Each AA is activated by reacting with an ATP

  • The activated AA is then attached to particular tRNA... (with the correct anticodon)


Elongation
Elongation

  • The new peptide is added on and the whole ribosome “translocates” or moves down one codon.

  • A new “A site” is available for another AA to add.


Termination
Termination

  • After the last translocation (the last codon is a STOP), no more AA are added.

  • “Releasing factors” cleave the last AA from the tRNA

  • The polypeptide is complete