Something to note is that I sometimes use my own Abbreviations because I'm lazy and in need of a coffee, anyone taking the exam: Unless its mRNA, tRNA, DNA, rRNA e.t.c. write it in full (i.e. Write Amino Acids, not AAs) otherwise, you might be marked down for not using proper terminology.
Feel Free to comment any questions you have :)
TRANSCRIPTION
- RNA Polymerase (an enzyme) Attaches to the DNA Double Helix at the Beginning of a Gene.
- The Hydrogen Bonds Break, separating the two strands, so the DNA Molecule Uncoils.
- One of the Strands is then used as a Template to make an mRNA Copy.
- The RNA Polymerase lines up free RNA Nucleotides next to the Template Strand.
- The Complimentary Base Pairs are found (A-T) (C-G) - Except for Adenine (A) which is paired with Uracil (U) instead of Thymine (T).
- The Complimentary Base Pairs are Joined together forming an mRNA Molecule.
- RNA Polymerase moves along the DNA Separating Strands and Assembling the mRNA Strand.
- Hydrogen Bonds Form once the RNA Polymerase has Moved on and the Strands Coil back into a Double Helix.
- When RNA Polymerase reaches a Stop Codon it Stops making mRNA and Detaches from the DNA.
- mRNA moves out of the nucleus through a Nuclear Pore and Attaches to a Ribosome in the Cytoplasm.
TRANSLATION
It occurs at the Ribosomes in the Cytoplasm. The AAs are Joined together to make a Polypeptide Chain Following the Sequence of Codons carried by the mRNA.
- The mRNA Attaches itself to a Ribosome and Transfer RNA molecules (tRNA) carry AAs to the Ribosome.
- A tRNA molecule with the Anticodon (A-U-G's Anticodon is U-A-C) and Attaches itself to the mRNA by Complimentary Base Pairing.
- A Second tRNA molecule Attaches itself to the Next Codon on the mRNA in the Same Way.
- rRNA in the Ribosome Catalyses the Formation of a Peptide Bond between the Two AAs attached to the tRNA molecules. This joins the AAs together. The First tRNA molecule Moves Away leaving the AA behind.
- A Third tRNA Binds to the Next Codon on the mRNA. Its AA Binds to the First Two and the Second tRNA Moves Away.
- This Process Repeats producing a Chain of Linked AAs (Polypeptide Chain) Until there is a Stop Codon on the mRNA molecule
- The Polypeptide Chain Moves Away from the Ribosome and the process is complete.
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