Answers to Homework Tasks

DNA helix unwinds Hydrogen bonds between base pairs break (DNA strand unzips) Free RNA nucleotides line up against their complimentary base partners on the DNA strand Hydrogen bonds form between DNA nucleotides and free RNA nucleotides Sugar-phosphate bonds are formed between RNA nucleotides on the 3’ end (by RNA polymerase) Hydrogen bonds between the primary mRNA transcript and the DNA template break Primary transcript is spliced before it leaves the nucleus to go to the cytoplasm DNA strands wind back up to form the double helix again

Questions A gene has coding sections – what are these called? A gene also has non-coding sections – what are these called? Which of these is removed from the primary transcript of mRNA? By what process? During transcription, all of the genetic information in a gene is initially copied into an RNA molecule - What is this called? What enzyme is responsible for transcription? The initial RNA molecule is ‘spliced’. Explain what this means and why the cell does this. 7) What name is given to the final mRNA which moves out of the nucleus into the cytoplasm? 8) Draw a diagram of the mRNA strand that would be transcribed from section X of the DNA molecule below: exons introns Introns are removed by splicing Primary mRNA transcript RNA polymerase Introns are removed and exons are joined together… The cell does this because introns contain non-coding regions that would result in the wrong / non-functional protein being made Mature mRNA transcript Section X A T C G G G C C A A T U A G C C C G G U U A or A U C G G G C C A A U T A G C C C G G T T A