Protein Synthesis

Question 1

Name the two general processes involved in protein synthesis.

Answer 1

Transcription, translation

Question 2

State the name of the major enzyme involved in transcription.

Answer 2

RNA polymerase

Question 3

State the function of a gene.

Answer 3

A unique sequence of DNA bases that codes for the production of a specific polypeptide (or RNA molecule).

Question 4

What is a codon and anti-codon?

Answer 4

Codon: 3 base code on a molecule of mRNA, encoding a specific amino acid.
Anticodon: 3 base code on tRNA, which is complementary to the 3-base codon on mRNA.

Question 5

State the role of mRNA in protein synthesis.

Answer 5

Carries a temporary copy of the gene in DNA to the ribosome where translation occurs.

Question 6

State the role of tRNA in protein synthesis.

Answer 6

Shuttles a specific amino acid to the ribosome where it binds (via anticodon) to codon on mRNA

Question 7

Describe the process of transcription.

Answer 7

• DNA unwinds and unzips (to expose the bases) at the start of the gene to be transcribed
• RNA polymerase adds free-floating nucleotides complementary to the template strand on DNA, to produce a single-stranded mRNA molecule.

Question 8

Describe the process of translation.

Answer 8

• mRNA binds to the ribosome
• tRNA carrying specific amino acids bind to the 3-base mRNA codons via their complementary 3-base anticodons.
• Amino acids are joined together by peptide bonds forming the polypeptide (which coils and folds into a functional protein).

Question 9

Explain why a triplet code is required to code for specific amino acids rather than just pairs.

Answer 9

There are 20 amino acids. A two base code does not give enough combinations 42= 16 to cover the 20 amino acids. 43= 64 combinations, allows for redundancy.