4.2 - DNA & Protein Synthesis

Question 1

Describe the structure of messenger RNA (mRNA)

Answer 1

A long, single strand.
Its base sequence is complementary to the DNA it was transcribed from.

Question 2

What does mRNA stand for?

Answer 2

Messenger RNA

Question 3

Suggest advantages of using mRNA rather than DNA for translation.

Answer 3

• shorter & contains uracil = breaks down quickly, so no excess polypeptide forms
• single stranded & linear = ribosome moves along strand & tRNA binds to exposed bases
• contains introns

Question 4

What does tRNA stand for?

Answer 4

Transfer RNA

Question 5

Describe the structure of tRNA

Answer 5

• single strand
• of approximately 80 nucleotides
• folded over into a clover leaf shape
  -one end = anti-codon
• opposite end = amino acid binding site

Question 6

What is produced by transcription?

Answer 6

mRNA

Question 7

Where does transcription take place?

Answer 7

The nucleus

Question 8

Outline the process of transcription.

Answer 8

• DNA uncoils into 2 strands with exposed bases.
• 1 strand is used as a template
• free floating nucleotides line up next to their complementary bases on template strand
• joined together by enzyme RNA polymerase

Question 9

What happens to mRNA after transcription?

Answer 9

In eukaryotic cells,
Pre-mRNA must be spliced - to remove introns,
Leaving only coding regions (exons)
Then it moves out of nucleus
And attaches to ribosome

Question 10

What is produced by translation?

Answer 10

Proteins

Question 11

Where does translation take place?

Answer 11

In the cytoplasm, on ribosomes

Question 12

Outline the process of translation.

Answer 12

• anticodon of tRNA attaches to complementary bases on the mRNA
• amino acids bonded to tRNA form peptide bonds, continuing to form a polypeptide chain until a stop codon is reached
• this process requires ATP