Protein Synthesis

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  • Created by: zoolouise
  • Created on: 24-05-16 16:02
What is transcription?
One strand of the DNA acts as a template for the production of mRNA, a complementary section of part of the DNA sequence. This occurs in the nucleus.
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What is translation?
The mRNA acts as a template to which complementary tRNA molecules attach, and the amino acids they carry are linked to form a polypeptide. This occurs on the ribosomes in the cytoplasm.
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What's the first stage of transcription?
Enzyme DNA helicase breaks hydrogen bonds between bases in a specific region of the DNA molecule, the two strands separate and unwind, exposing the nucleotide bases.
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What's the second and third stage of transcription?
Enzyme RNA polymerase binds to template strand of DNA at beginning of sequence to be copied. Free RNA nucleotides align opposite the template strand, based on complementary relationship between bases in DNA and free nucleotides.
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That's the fourth stage of transcription?
RNA polymerase moves along the DNA forming bonds that add RNA nucleotides, one at a time, to the growing RNA strand. This results in the synthesis of a molecule of mRNA alongside the unwound portion of DNA.
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What's the fifth and sixth stage of transcription?
The RNA polymerase separates from the template strand when it reaches a stop signal. The production of the transcript is complete, the newly formed RNA detaches from the DNA.
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What do the two subunits in ribosomes do?
Larger subunit has two sites for the attachment of tRNA molecules, two tRNA molecules are associated with a ribosome. The smaller subunit binds to the mRNA.
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What's the first stage of translation?
Initiation: a ribosome attaches to a start codon at one end of the mRNA molecule.
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What happens in initiation?
First tRNA with an anticodon complementary to the first codon on the mRNA attaches to the ribosome. 3 bases of codon on mRNA bond to 3 complementary bases of the anticodon on tRNA, with hydrogen bonds.
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(continued)
A second tRNA with an anticodon complementary to the second codon on the mRNA attaches to the other attachment site and the codon and anti-codon bond with hydrogen bonds.
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What's the second stage of translation?
Elongation: the two amino acids are sufficiently close for a ribosomal enzyme to catalyse the formation of a peptide between them
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What happens in elongation?
First tRNA leaves ribosome, leaving attachment site vacant, it returns to cytoplasm to bind to another copy of its specific amino acid. Ribosome moves one codon along mRNA strand, next tRNA binds.
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What's the final stage of translation?
Termination: the sequence repeats until a 'stop' codon is reached.
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What happened in translation?
The ribosome - mRNA - polypeptide complex seperates
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Card 2

Front

What is translation?

Back

The mRNA acts as a template to which complementary tRNA molecules attach, and the amino acids they carry are linked to form a polypeptide. This occurs on the ribosomes in the cytoplasm.

Card 3

Front

What's the first stage of transcription?

Back

Preview of the front of card 3

Card 4

Front

What's the second and third stage of transcription?

Back

Preview of the front of card 4

Card 5

Front

That's the fourth stage of transcription?

Back

Preview of the front of card 5
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