M2 Protein Synthesis

Question 1

Outline the processes of transcription and where it occurs.

Answer 1

mRNA copy of the gene is made in the nucleus.

1. RNA Polymerase attaches to the DNA. Hydrogen bonds break separating strands and DNA uncoils.
2. RNA Polymerase lines up free RNA nucleotides along the template strand and complementary base pairing result in the mRNA being complementary to the DNA template strand.
3. RNA Polymerase moves along DNA assembling mRNA strand. Hydrogen bonds between uncoiled strands reform and strands coil back to a double helix.
4. When RNA Polymerase reaches a stop codon, it stops making mRNA and detaches from DNA. Leaves via nuclear pores and attached to a ribosome.

Question 2

Outline the processes of translation and where it occurs.

Answer 2

Takes place in the ribosome. Amino acids are joined together by a ribosome to make a polypeptide chain.

1. mRNA attaches to a ribosome and tRNA molecules carry amino acids to the ribosome.
2. tRNA molecule with an anti-codon that is complementary to the start codon on the mRNA, attaches to the mRNA (complementary base pairing).
3. A second tRNA molecule attaches to the next codon on the mRNA.
4. rRNA, specifically peptidyl transferase catalyses the formation of peptide bonds between those 2 amino acids attached to the tRNA molecules.
   First tRNA molecule moves away leaving its amino acids behind.
5. A 3rd tRNA molecule binds to the next codon.
   Process repeats.
6. Process continues until a sop codon on the mRNA.
   Protein/polypeptide chain moves away from the ribosome.