DNA helicase acts on specific region of DNA molecule- breaks hydrogen bonds between bases forming 2 exposed DNA strands
RNA polymerase (activated by transcription factors) moves along template strand causing nucleotides on this strand to join with complementary nucleotides
Uracil replaces thymine
Nucleotides added one at a time to form pre- mRNA strand (complementary to DNA strand, condensation reactions)
DNA strands rejoin
when RNA polymerase reaches stop code it detaches and pre-mRNA strand produced.
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Splicing pre-mRNA
Forms mRNA
Introns (non coding regions) of mRNA removed (present as copied from DNA)
Exons are rejoined
mRNA can now pass out of the nucleus through a nuclear pore
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Translation
Ribosome attached to starting codon at one end of mRNA
tRNA molecule with complementary anticodon sequence moves to ribosome and pairs up with mRNA sequence
tRNA carries a specific amino acid
Complementary anticodon of tRNA pairs up with next codon on mRNA...
Ribosome moves along mRNA...
Amino acids are joined by peptide bonds through enzyme and ATP
Ribosome holds 2 tRNA molecules at a time
tRNA diffuses away
Process is repeated till stop codon of mRNA is reached
Polypeptide chain built up
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Post Translational Modifications
Polypeptide chain assembled into protein
Coiled or folded: Secondary
Further folded: Tertiary
Different ones linked: Quarternary
Proteins altered before becoming functional
Modifications carried out by enzymes: include chain cutting, adding methyl or phosphate groups to amino acids, adding sugars or lipids
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