AQA A level Bio 4.2 DNA and Protein Synthesis

Describe two differences between the structure of a tRNA molecule and the structure of an mRNA molecule. (2)

tRNA is 'clover leaf shape', mRNA is linear (1)

tRNA has an amino acid binding site, mRNA does not (1)

In a eukaryotic cell, the structure of the mRNA used in translation is different from the structure of the pre-mRNA produced by transcription.

Describe and explain a difference in the structure of these mRNA molecules. (2)

mRNA has no introns/has (only) exons (1)

(because of) splicing (1)

Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation. (3)

tRNA brings specific amino acid (to ribosome) (1)

Anticodon (on tRNA) binds to codon (on mRNA) (1)

Amino acids join by condensation reaction (using ATP) (1)

Describe how mRNA is produced from an exposed template strand of DNA.

Do not include DNA helicase or splicing in your answer (3)

(Free RNA) nucleotides form complementary base pairs (1)

Phosphodiester bonds form (1)

By (action of) RNA polymerase (1)

Describe how mRNA is formed by transcription in eukaryotes (5)

Hydrogen bonds (between DNA bases) break (1)

(only) one DNA strand acts as a template (1)

(Free) RNA nucleotides align by complementary base pairing (1)

(In RNA) Uracil is used in place of thymine (1)

RNA polymerase joins (adjacent RNA) nucleotides by phosphodiester bonds (1)

Describe how a polypeptide is formed by translation of mRNA (6)

(mRNA attaches) to ribosomes (1)

(tRNA) anticodons (bind to) complementary (mRNA) codons (1)

tRNA brings a specific amino acid (1)

Amino acids joined with the use of ATP (1)

tRNA released (after amino acid joined to polypeptide) (1)

The ribosome moves along the mRNA to form the polypeptide (1)

What is the proteome of a cell? (1)

The proteome is the full range of different proteins that a cell is able to produce (at a given time) (1)

Give the two types of molecule from which a ribosome is made.(1)

One of RNA and one of proteins (1)