Protein Synthesis

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Chapter 12

• Protein Synthesis
• (the making of protein)
• Starring DNA MAN

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• LOOK! Up in the nucleus! Its a double helix!
  Its a spiral staircase!
• No.. Its
• DNA MAN!!!

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• (Part II of our continuing saga about the Life
  and Times of DNA Man)
• Sadly, when we last left our Superhero, he was in
  the nucleus, all twisted up with no place to go.

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• Unzip, copy, rezip. Unzip, copy, rezip. Day in
  and day out. Thats all I seem to do around
  here. sighs DNA MAN. Is replication
• all there is to
• life?

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• Just at that moment, a collective call arises
  from somewhere out in the distant cytoplasm We
  need protein! We want protein! Wheres our
  protein?

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• AHA! exclaims our
• superhero, Theres trouble
• in paradise. They need my
• secret plans for
• making protein.
• This is a job for
• .da da ta da...
• DNA MAN!

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• Quick as a flash, DNA MAN
• races toward the nuclear
• membrane. But, alas, he
• finds himself too large to
• squeeze through the
• small nuclear pores.
• Whats a superhero
• to do?

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• Of course! shouts DNA MAN, I know what Ill
  do. Ive got the perfect solution!

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• Can DNA MAN solve this problem? Will he be able
  to smuggle the secret plans for making proteins
  from his impenetrable fortress to the needed
  destination? Can he? Will he? What will DNA
  MAN do????????

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STEP 1(X-rated)

• DNA unzips its genes and exposes its bases.

DNA strand
unzipping
DNA strand
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Sdjkfljsadfjkasdjfkasdkfla
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Step 2

• Free-floating nucleotides, in the nucleus, join
  to one side (the coding side) of DNAs exposed
  bases,

Fjaklsdfjkasdj f
Jaksdlfjkasdjfkasdjfasdjfkasdjfkasdjfklasdj
fkasdjfka
Asdkfjlasdjfkasdjfkasdjfk
Jakdfjlasdfj
Jfksldjfasdfasdfasdfasdfasdfsdfa
DNA
Sdkalfjkasdfjasdfjkasdffjadjf
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The DNA zips closed and remains in the nucleus.
jasdfffffasdfasdf
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• This RNA molecule is called messenger RNA (now
  carrying the genetic message).
• (mRNA messenger RNA).

sdjfklaasj
mRNA
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Characteristics of mRNA

• Is composed of ribose sugar
• Is only 1/2 of a ladder in size
• Has nitrogen bases A, G, C, and U (uracil)

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• Example
• If the DNA code was
• ATGCGAAAGTTC
• Then the transcribed RNA code would be
• UACGCUUUCAAG

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• The process of DNA making RNA is called

TRANSCRIPTION
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• The code that DNA gives to mRNA is arranged in
  groups of 3 nitrogen bases called a codon.
• EXAMPLE
• DNA Code ATG - GAC - TAG
• mRNA Code UAC - CUG - AUC

U A C
C U G
A U C
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Step 3

• mRNA leaves the nucleus, carrying the code, and
  travels to the ribosomes.

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Step 4

• Once at the ribosomes, mRNA makes a complimentary
  copy of itself, called transfer RNA,
• and thereby passes the code onto tRNA.
• (tRNA transfer RNA)

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• The code on tRNA consists of a group of three
  nitrogen bases called an anticodon.
• EXAMPLE
• mRNA UAC - CGG - AUA - CGA
• tRNA AUG - GCC - UAU - GCU

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Step 5

• tRNA leaves the ribosomes and travels out into
  the cytoplasm. There, tRNA collects amino acids
  that match the anticodons. tRNA takes the amino
  acids back to the ribosomes.

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• The ribosomes read the code on mRNA and arrange
  the arriving amino acids into their proper
  sequence.

Dfjdjklsafjfjdk
a
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Aklsadfkasdlf
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• The ribosomes continue to read the mRNA code, and
  place arriving amino acids in order, until a
  stopcodon is read. The result of hooking
  together long chains of amino acids is

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VOILA!

• PROTEIN!

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• The process of RNA making protein is called

TRANSLATION
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Question?

• How many codons (groups of three nucleotides) are
  possible from the 4 letter nucleotide
  alphabet?
• (U, A, C, G)

64
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Question?

• How many amino acids are coded for by these 64
  codons/anticodons?

20
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Question?

• How can 64 codons/anticodons only code for 20
  amino acids?

Two or more codons can code for the same amino
acid.
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For more help, tutorials, animations and practice
problems.
Animation tutorial
Interactive tutorial
Animated tutorial
Tutorial
Game
Animated tutorial
Animated tutorial
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Sources

• http//gslc.genetics.utah.edu/units/basics/transcr
  ibe/
• http//omega.dawsoncollege.qe.ca/ray/protein/panin
  .htm
• http//www.biostudio.com/demo_freeman_protein_synt
  hesis.htm
• http//www.brookscole.com/chemistry_d/templates/st
  udent_resources/shared_resources/animations/protei
  n_synthesis/protein_synthesis.html
• http//www.gravytrainproductions.com/transcription

33
continued

• http//www.lewport.wnyric.org/jwanamaker/animation
  s/Protein20Synthesis20-20long.html
• http//www.nature.ca/genome/03/c/10/03c_13a_e.cfm
• http//www.pbs.org/wgbh/aso/tryit/dna/
• http//www.thinkquest.org/library/site_sum.html?tn
  ameC004535urlC004535/dna_transcription.html
• http//www.wisc-online.com/objects/index.asp?objID
  AP1302