Genetic Code & Cell Function
- Created by: beth-marie2511
- Created on: 18-06-16 21:20
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- Genetic Code & Cell Function
- Protein Synthesis
- Transcription
- 1. DNA helicase acts on a specific region of the DNA molecule
- It breaks the hydrogen bonds between DNA bases
- Strands unzip and unwind to expose the nucleotide bases
- 2. RNA polymerase links to the DNA template strand (about to be transcribed)
- RNA polymerase catalyses the free RNA nucleotides to the template strand
- Complimentary base pairing
- RNA polymerase catalyses the free RNA nucleotides to the template strand
- 3. RNA polymerase moves along DNA to form bonds between the RNA nucleotides
- Free RNA nucleotides attach to the chain to produce mRNA (alongside the unzipped piece of DNA)
- Behind RNA polymerase the DNA strands rewinds and returns to a double helix
- 4. RNA polymerase separates when it reaches a 'stop' codon
- mRNA production is now complete
- 5. mRNA carries DNA code out of the nucleus, through the nucear pores and into the cytoplasm
- This is where the mRNA attaches itself to a ribosome
- 1. DNA helicase acts on a specific region of the DNA molecule
- Translation
- Translating codons on mRNA into a sequence of amino acids to a polypetide
- 1. Ribosome becomes attached to the 'start' codon at one end of the mRNA molecule
- 2. 1st tRNA with anticodon complimentary to the first codon on the mRNA attaches itself to the ribosome
- A second tRNA with the second anticodon complimentary to the second codon of the mRNA molecule attaches itself to the ribosome etc.
- 3. The two amino acids on the tRNA molecules are close enough to form a peptide bond
- 1st tRNA leaves the ribosome which leaves an attachment site vacant
- Ribosome now moves one codon along the mRNA strand
- 4. Polypeptide 'grows' a an attachment becomes vacant it is occupied by another tRNA with a complimentary anticodon to the codon of the mRNA.
- As the ribosome moves along the mRNA a polypeptide forms
- 5. There may be several ribosomes on a single mRNA
- Each one reading from the coded information at the same time
- Polysome system
- Many polypeptides form
- Polysome system
- Each one reading from the coded information at the same time
- Transcription
- Protein Synthesis
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