Simplified Process

• DNA → mRNA (messenger RNA):

  Inside the nucleus, DNA is transcribed into messenger RNA (mRNA), which carries the genetic code for making a specific protein.

• mRNA travels to ribosomes:

  The mRNA leaves the nucleus and goes to a ribosome in the cytoplasm or on the rough ER.

• Ribosomes read mRNA:

  Ribosomes “read” the sequence of the mRNA in groups of three bases called codons.

• tRNA brings amino acids:

  Transfer RNA (tRNA) brings the correct amino acids to the ribosome based on the codon.

• Ribosomes assemble proteins:

  The ribosome links the amino acids together in the right order to form a polypeptide chain, which folds into a functional protein.

D1.2.1— Transcription as the synthesis of RNA using a DNA template.

• Transcription can be defined as the process of RNA polymerase using a DNA sequence to synthesise a strand of RNA that have complementary nucleotides to the DNA
• Transcription is where the DNA in the nucleus into a message, so it takes place inside the nucleus. Here, a special kind of RNA known as RNA polymerase, connects complementary RNA Bases to DNA bases, to form mRNA, or Messenger RNA. → This however is not a straightforward process, and a significant amount of mRNA editing occurs.

Functions of RNA polymerase in Transcription:

• RNA polymerase breaks down hydrogen bonds between two strands of DNA in order to use one of the strands as a template to synthesise mRNA, though it’s more like pre-Mrna because it only becomes mRNA after something called introns, or simply a substance that allows a gene to code for multiple transcripts is removed
• RNA Polymerases recognise and bind to specific DNA sequences known as promoters, essentially helping KNOW which sequences to bind to after the two strands have been separated, creating the starting point for transcription (DNA strands goin pick me, choose me, love me)
• RNA Polymerase also helps in ELONGATION making sure that it moves along the template strand adding nucleotides in a 5’ to 3’ direction
• RNA is also like your friendly neighbourhood newspaper editor, it proofreads the RNA chain synthesised to make sure no mistakes have been made in the complementary base pairing
• Finally, RNA Polymerase RECOGNISES specific termination signals on the DNA template, so it recognises when to stop (unlike some ex boyfriends)

D1.2.2— Role of hydrogen bonding and complementary base pairing in transcription

The Complementary Base Pairings in Transcription:

• Since Transcription involves the synthesis of mRNA, a type of RNA, the complementary base pairings are as follows:
• AUGC - ADENINE WITH URACIL, GUANINE WITH THYMINE