First 263 words of the document:
Name and describe the structures where the polypeptide chain of this enzyme would be
synthesised. (2 marks)
On the ribosomes which may be on the rough endoplasmic reticulum.
Ribosomes are protein components which are made of two sub units 1 large and 1
smaller sub unit.
Explain what is meant by the term gene mutation? (2 marks)
There is a change in the DNA
Due to a insertion, deletion or substitution of bases (nucleotides)
Describe how free nucleotides are bonded together in the correct sequence in pre-mRNA, at
stage A (transcription) (3 marks)
The sequence of bases (nucleotides) on DNA determines the sequence on mRNA
It is done by complementary base pairing : e.g. AU / CG / GC / TA (DNA: mRNA)
There is formation by condensation reactions
Phosphodiester bonds are created
RNA polymerase catalyses the reaction.
Explain the function of the codons at each end of a strand of mRNA, during the process of
translation. (2 marks)
There are stop and start codons
Start codons are needed to begin polypeptide synthesis and stop codons end
Suggest why a variety of different protein structures could be formed from the polypeptides
synthesised using the mRNA molecules from a single gene. (3 marks)
There are different variations of extrons.
Creating different primary structures
The secondary/tertiary structures of proteins depend on the primary structure.
Therefore different 3D shapes are produced.
There are changes in the different bonds e.g. hydrogen, ionic and disulphide bonds.