2.3.7 Transcription

Question 1

2 stages of proteinsynthesis

Answer 1

• Transcription
• Translation

Question 2

What is transcription?

Answer 2

• Occurs in nucleus
• DNA helicase breaks hydrogen bonds between complementary base pairs (DNA unwinds)
• Exposed genes can be transcribed
• Free RNA nucleotides align with template strand and form hydrogen bonds with their complementary bases
• RNA polymerase moves in 3’ to 5’ direction, catalysing formation of phosphodiester bonds forming the sugar phosphate backbone of RNA (mRNA grows in 5’ to 3’ direction)
• When gene has been transcribed (single strand of mRNA molecule is complete), hydrogen bonds break and the double stranded DNA molecule reforms (Coding strand and template strand come together, where hydrogen bonds between complementary base pairs reform)
• mRNA contains uracil instead of thymine
• mRNA strand leaves nucleus via pores in nuclear envelope