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Translation. PROTEIN SYNTHESIS. Transcription = Nucleic acid sequence (a gene)  an identical copy of the Nucleic acid sequence (mRNA) Translation = Nucleic acid sequence (mRNA)  a sequence of Amino acids (a protein).

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Translation

Translation

PROTEIN SYNTHESIS


  • Transcription = Nucleic acid sequence (a gene)  an identical copy of the Nucleic acid sequence (mRNA)

  • Translation = Nucleic acid sequence (mRNA)  a sequence of Amino acids (a protein).

  • How do we decode the sequence of nucleotides on mRNA and turn it into a sequence of amino acids (a protein)?


How many different amino acids are there?

So can one base code for one amino acid ex. Can adenosine (the base) code for tryprophan (an amino acid)?

Can two bases?

What about three?


Meet tRNA … “the decoder”

  • There are 64 species of tRNA, each species recognizes the code for an amino acid or a start or stop signal

  • Why 64?


Codons and Anticodons

  • A codon is a group of three nucleotides on an mRNA molecule

  • An Anticodon is the complimentary group of three nucleotides on a tRNA

  • When the codon is recognized by the complimentary anticodon on the tRNA the correct amino acid corresponding to that codon is made available.


4 components used in translation
4 Components used in Translation

  • mRNA- the message to be translated into protein.

  • Amino acids- the building blocks that are linked together to form the protein.

  • Ribosomes- the “machines” that carry out translation.


  • tRNA(transfer RNA)- brings an amino acid to the mRNA and ribosome.

    • One end of a tRNA molecule has an anticodon that complements with an mRNA codon.

    • The other end has a specific amino acid.

    • A tRNA molecule with a particular anticodon always carries the same type of amino acid.


How does translation occur
How does translation occur?

  • The ribosome binds to the mRNA molecule.

  • The tRNA with the anticodon that complements the first codon on the mRNA binds to the first site on the ribosome.

  • Another tRNA with the anticodon that complements the second codon on the mRNA binds to the second site on the ribosome.


  • A peptide bond forms between the first two amino acids.

  • The first tRNA leaves, and the ribosome moves along the mRNA to the next codon.

  • The next tRNA brings in the next amino acid, and a peptide bond is formed between this amino acid and the growing amino acid chain.

  • The process continues with the ribosome moving along the mRNA molecule and the amino acids linking together until a STOP codon is reached.



CODONS

mRNA nucleotides are translated in groups of 3 called codons.

AUGCACUGCAGUCGAUGA


Each codon codes for a specific amino acid. 20 different amino acids can be used in different combinations to form a protein.

For example:

mRNA codonamino acid

AAU asparagine

CGC arginine

GGG glycine


Amino acid sequence determines the 3 d protein shape
Amino Acid sequence determines the 3-D protein shape amino acids can be used in different combinations to form a protein.

  • Interactions between amino acids cause folding and bending of the chain

    Examples:

    • positive (+) and negative (-) parts of amino acids are attracted to each other.

    • hydrophobic regions are attracted to each other

  • Folding

    http://www.stolaf.edu/people/giannini/flashanimat/proteins/hydrophobic%20force.swf

  • Structure levels

    http://www.stolaf.edu/people/giannini/flashanimat/proteins/protein structure.swf


How is the amino acid sequence determined
How is the amino acid sequence determined? amino acids can be used in different combinations to form a protein.

  • The mRNA

  • Each codon is a code for one amino acid

    DNA sequence: T A C C G A G A T T C A

    mRNA sequence: A U GG C UC U AA G U

    amino acid sequence: Met -- Ala -- Leu -- Ser


Your turn
Your turn amino acids can be used in different combinations to form a protein.

  • Decoder construction-DNA Bingo

  • Translation exercise (Find the secret message)

  • Genes to proteins-practice worksheet.

    • or

  • Complete the “Translation Practice” worksheet


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