Transcript Translation/Protein Synthesis

TRANSLATION/PROTEIN
SYNTHESIS
Unit 4 – Part 1
Central Dogma
DNA
mRNA
Proteins
Traits
DNA vs. RNA Review
Deoxyribonucleic acid
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DNA
Double stranded
Made up of repeating units
called nucleotides
Contains the 5 C (pentose) sugar
Deoxyribose
Found in the nucleus
4 nitrogen bases
 Adenine, Guanine, Cytosine,
Thymine
Ribonucleic acid
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RNA
Single Stranded
Made up of repeating units
called nucleotides
Contains the 5 C sugar ribose.
Found in the nucleus & cytoplasm
4 nitrogen bases
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Adenine, Guanine, Cytosine, uracil
3 forms
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mRNA, rRNA, tRNA
Transcription Review
DNA  mRNA
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DNA makes proteins, which control all of our traits,
but DNA cannot leave the nucleus.
Therefore it has to find a way to get it’s message
from the nucleus to the cytoplasm where the protein
factories are (ribosomes).
Transcription Review cntd.
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The enzyme RNA polymerase attaches to a strand
of DNA and begins to unwind and unzip the strand.
It also adds the RNA nucleotides to the undone DNA
strand one at a time making a mRNA strand.
Transcription Review cntd.
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Eventually RNA polymerase will reach a spot on the
DNA that signals it to stop making the mRNA strand.
After it reaches this point it can let go and leave the
nucleus.
From the nucleus it goes into the cytoplasm and
attaches to a ribosome.
Translation/Protein Synthesis
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Step where the mRNA code is translated into an
amino acid sequence: MRNA to protein
 A series of amino acids
Also called protein synthesis because this is the step
where proteins are made.
Translation/Protein Synthesis
Translation/Protein Synthesis
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RNA is read 3 nitrogen bases at a time
 Each triplet of bases is called a codon
Each 3 letter codon is a code for an amino acid
A series of 50-5,000 amino acids make up a protein.
Translation/Protein Synthesis Steps
1. Once the mRNA sequence leave the nucleus it
attaches to the ribosome
2. The ribosome (which is partly made up of an rRNA
molecule) travels down the mRNA sequence until it
finds a start spot called a start codon
 AUG: the ONLY start codon
3. The start codon is the spot where the amino acids
start to make proteins.
Translation/Protein Synthesis Steps
4. After the ribosome finds the start codon a transfer
RNA molecule (tRNA) attaches to the codon by an
anti-codon and carries an amino acid.
 Each tRNA anticodon carries only ONE amino
acid.
5. Amino acids are deposited until it reaches one of 3
stop codons.
 UAA, UAG, UGA
6. After a stop codon is reached, the amino acid chain
is let go and a protein is formed.
Translation/Protein Synthesis Steps
Translation/Protein Synthesis Steps
Translation/Protein Synthesis
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How does the tRNA molecule know what amino acid
to drop off?
Each codon(mRNA) matches a specific anticodon
(tRNA). Each anticodon matches a specific amino
acid.
Codon Chart:
To determine what amino acid matches which codon
refer to the codon chart.