Transcription

Question 1

Stage 1 Transcription

Answer 1

The enzyme helicase breaks the hydrogen bonds between the bases in a specific region of double-stranded DNA in the nucleus causing the two strands to seperate

Question 2

Stage 2 Transcription

Answer 2

RNA polymerase binds to a base sequence called the promoter region. This determines which way the RNA polymerase faces, and hence which region is used as a template

Question 3

Stage 3 Transcription

Answer 3

RNA polymerase moves along the DNA strand in the 5’ to 3’ direction. As it passes over the DNA bases, it forms a complementary mRNA strand from free RNA nucleotides in the nucleus

Question 4

Stage 4 Transcription

Answer 4

As the mRNA strand is produced the two strand of DNA start to recoil behind it

Question 5

Stage 5 Transcription

Answer 5

When a terminator region is reached the DNA is no longer copied. The mRNA is now ready for the next stage of protein synthesis - translation

Question 6

Before Transcription

Answer 6

A gene needs to be stimulated by a regulatory protein, called a transcription factor

Question 7

Transcriptional Factor

Answer 7

Contains sites that bind to a specific region of the DNA, cannot initiate transcription alone but form a pre-initiation complex with RNA polymerase

Question 8

Processing of RNA

Answer 8

DNA contains some regions that do not code for proteins known as introns. To produce functional proteins, these introns need to be spliced out of the mRNA, leaving only the regions that code for proteins, called exons. A molecule called a spliceosome removes the introns, producing mature mRNA that contains only exons. Before splicing, mRNA is known as pre-mRNA