Proteins are made in the ribosomes outside the nucleus.

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• Proteins are made in the ribosomes outside the
  nucleus.
• DNA is copied (replicated) in the nucleus but
  cannot leave the nucleus.
• THEREFORE.

• A message must be sent to the ribosomes in the
  cytoplasm telling them what proteins to make.
• This message is carried by a nucleic acid called
  messenger (mRNA ).

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RNA Structure
RNA differs from DNA in 4 ways

1. RNA is a ______________________
2. RNA has the sugar ____________________
3. Adenine bonds with __________ (NOT thymine).
4. _______________ leave the nucleus

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KEY CONCEPT __________________ converts a gene
into a single-stranded RNA molecule.
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RNA carries DNAs instructions.

• The central dogma states that information flows
  in one direction from DNA to RNA to proteins.

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• The central dogma includes three processes.
• ______________
• ______________
• ______________
• RNA is a link between DNA and proteins.

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Transcription copies DNA to make a strand of RNA.
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• Transcription occurs in two major steps.
• DNA unzips unwinds at the start of a gene.

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• Transcription occurs in two major steps.
• Nucleotides pair with their complementary bases
  on one strand of the DNA.
• RNA polymerase bonds the nucleotides together.
• The DNA helix winds again as the gene is
  transcribed.

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The RNA strand detaches from the DNA once the
gene is transcribed. Then it leaves the nucleus
and heads to a _______.
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• Transcription makes three types of RNA.
• ________________(mRNA) - carries the message that
  will be translated to form a protein.
• ________________(rRNA) - forms part of ribosomes
  where proteins are made.
• ________________(tRNA) - brings amino acids from
  the cytoplasm to a ribosome.

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KEY CONCEPT ___________________ converts an mRNA
message into a polypeptide, or protein.
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Amino acids are coded by mRNA base sequences.

• Translation converts mRNA messages into
  polypeptides.
• A ___________ is a sequence of three nucleotides
  that codes for an amino acid.

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The language of amino acids is based on codons
1 codon 3 mRNA nucleotides
1 codon 1 amino acid
A U A U A U G C C C G C
How many codons are in this sequence of
mRNA? How many Amino Acids does this gene code
for?
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• The genetic code matches each codon to its amino
  acid or function.

• three stop codons
• one start codon, codes for methionine

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How to read a codon table

• Use in protein synthesis for translating the mRNA
  code into amino acid sequence

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You need a sequence of mRNA

• Where does this come from?

From the transcription of DNA --gt mRNA
Example
DNA sequence TAC GGA CAT AAC ACC TGC
ATC mRNA sequence
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Transcription

• mRNA sequence leaves the nucleus and travels to
  the cytoplasm to a free floating ribosome or to
  the rough ER.
• It will attach to the ribosome and begin the
  second step of protein synthesis, translation.

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Translation

• mRNA is read as a series of codons (three
  letters) within the ribosome.
• tRNA molecules have an ____________ sequence of
  letters that are complements to the mRNA
• ex mRNA CGA UCC (codon)
• tRNA GCU AGG (anticodon)

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So now we get to the codon table!

• Locate the first letter of your codon using the
  left side of the table.
• Ex. AUG
• look for the A

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• Now move to the second letter of your codon which
  is U
• Look at the top of the table where you see the
  title 2nd letter
• Find the letter U and follow it down until it
  intersects with the letter A from the left
  side.
• You should see four amino acids (isoleucine,
  isoleucine, isoleucine, and (start) methionine.

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• Down to the last letter of the codon!
• Look to the right hand side for the third letter.
  Find the letter G which will intersect with
  the box that had our four choices.
• Move your finger from the G on the left over to
  the left and you should land on .. Methionine
  (start)
• Yes you did it!!!
• Now try another codon

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Using this chart, you can determine which amino
acid the codon codes for!
Which amino acid is encoded in the codon CAC?
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Notice there is one start codon AUG.
Transcription begins at that codon!
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Notice there are three stop codons.
Transcription stops when these codons are
encountered.
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What do these codons have to do with proteins?

• Each codon represents an amino acid that will
  eventually form a protein that is used within a
  cell.
• Proteins are made up of hundreds of amino acids
  in a specific sequence.
• When they get out of order a mutation occurs.

Long string of amino acids will form
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• A change in the order in which codons are read
  changes the resulting protein.

• Regardless of the organism, codons code for the
  same amino acid.

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Amino acids are linked to become a protein.

• An anticodon is a set of three nucleotides that
  is complementary to an mRNA codon.
• An anticodon is carried by a tRNA.

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• Ribosomes consist of two subunits.
• The large subunit has three binding sites for
  tRNA.
• The small subunit binds to mRNA.

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• For translation to begin, tRNA binds to a start
  codon and signals the ribosome to assemble.
• A complementary tRNA molecule binds to the
  exposed codon, bringing its amino acid close to
  the first amino acid.

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• The ribosome helps form a peptide bond between
  the amino acids.

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• The now empty tRNA molecule exits the ribosome.

• Once the stop codon is reached, the ribosome
  releases the protein and disassembles.

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From gene to protein
_______________
_______________
protein
mRNA
DNA
trait
nucleus
cytoplasm
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cytoplasm
transcription
transcription
transcription
nucleus
transcription
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From gene to protein
protein
transcription
translation