DNA & Protein Synthesis

Question 1

Describe structure of messenger RNA

Answer 1

Long, single strand. Base sequence is complementary to DN it was transcribed from

Question 2

Suggest advantage of using mRNA rather than DNA for translation

Answer 2

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

Question 3

Describe structure of transfer RNA (tRNA)

Answer 3

Single strand of around 80 nucleotides that is folded over into clover leaf shape. On 1 end is anti-codon, on opposite end is amino acid binding site

Question 4

Outline process of transcription

Answer 4

• DNA uncoils into 2 strands with exposed bases. One is used as template
• Free nucleotides line up next to their complementary bases, & are joined together by RNA polymerase

Question 5

What happens to mRNA after transcription?

Answer 5

In eukaryotic cells, pre-mRNA must be spliced to remove introns, leaving only coding regions. Then moves out of nucleus & attaches to a ribosome

Question 6

Outline process of translation

Answer 6

• Anti-codon of tRNA attaches to complementary bases on mRNA
• Amino acids bonded to tRNA form peptide bonds, continuing to form polypeptide
• Process requires ATP