Transcription and Translation

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Is the formation of the proteins using information coded on DNA and carried out by RNA
STEP 1 RNA Transcription
STEP 2 RNA Translation
DNA RNA Proteins

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Each protein molecule is made up of one or more polypeptides.
Each polypeptide is made up of a sequence of amino acids.
There are 20 different types of Amino
Acids.
Amino Acids Polypeptides
Proteins

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System that contains information needed for proper cell functioning.
This information is built into the arrangement of nitrogen bases.

 A specific group of three sequential bases on mRNA.
 Each codon codes for a specific amino acid.
There are 64 possible codons. Coding for amino acids is universal for all animals.
 See Codon chart on Page 207
 What does the following mRNA code for?
AUG UUU CCU CAA GGU GAG GCG ACA UAA

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First step in protein synthesis
Occurs in the nucleus
End result is RNA molecule with a
complementary base sequence to DNA.
Flow of Genetic Information
DNA RNA

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Enzyme called RNA Polymerase binds to DNA molecule at the promoter
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Promoter is a sequence of nucleotides on a DNA molecule where transcription will begin
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Once RNA polymerase binds to the DNA molecule it will unwind and separate the two complementary DNA strands.

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RNA polymerase adds free RNA nucleotides that are complementary to the nucleotides on one of the DNA strands.
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They will attach by hydrogen bonds and form a strand on messenger RNA.
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RNA polymerase will also establish the sugar to phosphate bonds between the nucleotides in the new mRNA strand.
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As the RNA Polymerase passes the separated DNA strands rewind.

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The enzyme will reach a pattern of bases on the
DNA strand that signals termination.
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The enzyme will stop and release the new RNA strand.
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The new RNA strand now moves to the cytoplasm

Transcription just created a RNA molecule with a complementary base sequence to
DNA.
Each type of RNA molecule (tRNA, mRNA, rRNA) is made this way and will start their job in protein synthesis.

Transcribe a mRNA molecule from the following DNA Strands.
DNA: TAC ATA TAA CGC CCG AGC TGC GGC

Transcribe a mRNA molecule from the following DNA Strands.
AGG TTA GGC CCG ATA AGC GCG GGC
Today:
Homework:

The process of assembling protein molecules from information encoded in mRNA.
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Second Step in Protein Synthesis
This process uses all three types of RNA
Process occurs in the cytoplasm

Transfer RNA (tRNA) bears a sequence of three bases called the Anticodon.
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The anticodon base sequence is complimentary to the codon on the mRNA tRNA carries an amino acid to the ribosome's mRNA and tRNA will pair together during translation.

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Process starts when mRNA migrates out of nucleus by nuclear pores, and migrates to the ribosome's.
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Amino acids floating freely in the cytoplasm are transported to the ribosome's by the tRNA

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The assembly of polypeptides start when the ribosome's attaches to the AUG(start) codon of the mRNA
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The AUG codon pairs with the anticodon
UAC on a specific tRNA
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Methionine is usually the first amino acid
(not always the first in the amino acid chain because it may be removed)

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The Polypeptide chain is put together.
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Ribosome's moves along the chain and decodes the mRNA and attaches the amino acids together by peptide bonds.
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The tRNA will bring in the next amino acid, pair up with the codon on the mRNA and attach the next amino acid together

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Eventually the ribosome reaches a stop codon and the process comes to the end
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The new polypeptide is complete and released.
Ribosome's may be working at different parts of the mRNA simultaneously.

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The components of translation separate.
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The last tRNA leaves.
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The Ribosome leaves the mRNA
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The translation machinery are now ready to translate another mRNA

DNA: TAC ATA TAA CGC CCG AGC TGC GGC mRNA:
Amino Acid Chain: