September 5, 2022
In this chapter of AS/A-level Biology, we will study Protein Synthesis & Genetic Code.
Protein Synthesis
Describe how messenger RNA is made during transcription [5]
- RNA polymerase unwinds the DNA double helix
- RNA polymerase breaks the hydrogen bonds
- In AS/A-level Biology, One strand is used as an anti- sense strand which contains the start codons to the stop codon
- RNA nucleotides line up along the strand and complementary base pairing occurs
- The nucleotides join by condensation reactions
Describe how proteins are made in translation [5]
- tRNA carries amino acids and the anti codon to the mRNA in the ribosomes
- the anti codon is complementary to the start codon on the mRNA
- Complementary base pairing occurs
- A second tRNA molecule attaches itself to the next codon the same way
- tRNA provides specific amino acids
- Two amino acids join by peptide bonds by condensation reactions
- Once a stop codon is reached a polypeptide chain forms and moves away from the ribosomes
Describe the structure of tRNA [4]
- Clover shaped
- Contains anti codons
- Has an amino acid binding site
- Has hydrogen bonds
Describe the structure of mRNA [3]
- When it comes to AS/A-level Biology, It is straight
- The length depends on the size of the gene
- It contains codons
What is meant by a template for the synthesis of mRNA ?
- RNA nucleotides attach to it
Genetic Code
Explain the nature of the genetic code [4]
- Triplet codons
- That code for an amino acid
- In AS/A-level Biology curriculum, Non overlapping, meaning triplet codons do not share their bases
- Degenerate, meaning amino acids are coded by more than one triplet
That's it! You got it!!