A3. RNA and Protein Synthesis

Question 1

What is protein synthesis?
Protein synthesis is the production of proteins (polypeptides) from the information contained within a cell’s DNA. It’s also known as polypeptide synthesis.
It involves two main stages: (2 things with brief description)

Answer 1

Transcription - where the DNA code is copied into a molecule called mRNA

Translation - where the mRNA joins with an organelle called a ribosome and the code it carries is used to synthesise a protein

Question 2

RNA - Messenger RNA (mRNA)

Where is it made?
What does it do briefly?
What is its structure?
What are groups of 3 called here?

Figure 1: The structure of mRNA.

Answer 2

• mRNA is made during transcription
• It carries the genetic code from the DNA to the ribosomes, where it’s used to make a protein during translation.
• mRNA is a single polynucleotide strand.
• In mRNA, groups of three adjacent bases are usually called codons (they’re sometimes called triplets or base triplets).

Question 3

Transfer RNA (tRNA)

Where is it used?
What does it do briefly?
What is its structure?
What are groups of 3 called here?

Figure 2: The structure of tRNA.

Answer 3

• tRNA is involved in translation.
• It carries the amino acids that are used to make proteins to the ribosomes.
• tRNA is a single polynucleotide strand that’s folded into a clover shape. Hydrogen bonds between specific base pairs hold the molecule in this shape.
• Every tRNA molecule has a specific sequence of three bases at one end called an anticodon. It also has an amino acid binding site at the other end.