Topic 1- DNA and protein synthesis

Question 1

DNA synthesis- stage 1

Answer 1

• double helix unwinds
• H bonds are broken
• bases on each strand exposed
• catalysed by DNA helicase

Question 2

DNA synthesis- stage 2

Question 3

DNA synthesis- stage 3

Answer 3

-DNA replicated in segments
- DNA ligase joins segments together
- two identical DNA mols. formed
- semi-conservative replication, each strand contains 1 copy of OG DNA

Question 4

Protein synthesis- transcription

Answer 4

• DNA helicase catalyses breaking of H bonds, leading to unwind
• anti-sense strand of DNA acts as template
• complementary base pairing
• H bonds form between bases while ph. bonds form
• RNA polymerase catalyses formation of ph. bonds between adjacent RNA nucleotides, forming mRNA
• mRNA leaves nucleus

Question 5

Protein synthesis- activation of amino acid

Answer 5

• mRNA codon attaches to anti-codon of tRNA
• tRNA transports mRNA to ribosome

Question 6

Protein synthesis- translation

Answer 6

• protein chain assembled in ribosome
• assembled on aa at a time
• ribosome reads mRNA ‘start’ codon
• codon and anti-codon held in place H bonds while aa join by peptide bonds
• process continues until ‘stop’