1. SBI 4U November 14 th, 2012

2. 1. What is the central dogma? 2. Where does translation occur in the cell? 3. Where does transcription occur in the cell? 4. In simple words, what is translation?

3. 1. Initiation 2. Elongation 3. Termination

4.  Locates the correct spot on the original DNA template where transcription is to begin  Promoter sequence: a particular nucleotide sequence on the DNA molecule  provides a binding site for RNA polymerase

5.  Strings of A’s and T’s  RNA polymerase can only transcribe in one direction  RNA polymerase opens up a section of the DNA to be transcribed

6.  Copies the correct number of nucleotides from the DNA template onto a particular type of RNA molecule called messenger RNA (mRNA)

7.  RNA polymerase works from 5’ to 3’  As RNA polymerase passes, DNA helix re- forms and the mRNA strand separates from its template DNA strand  Template strand: strand used for transcription  Coding strand: strand that is not used for transcription  identical to the template strand, except for ___________

8.  Signals the right place to stop the copying process to make sure the mRNA molecule contains the complete set of instructions from the gene

9.  Once transcription has been successfully initiated, the RNA polymerase continues along the DNA molecule until it encounters terminator sequences  After termination  mRNA separates from the RNA polymerase  Prokaryotes vs. Eukaryotes

10. Capping and Tailing:  5’ cap added to the 5’ end of the pre-mRNA  modified G nucleotide  Poly-A tail added to the 3’ end  long series of A nucleotides

11.  5’ cap and poly-A tail  help protect mRNA from enzymes in the cytoplasm that may break it down. Also serve as signals. Poly-A tail also helps with transport of the mRNA

12. mRNA Splicing:  Exons: form part of the instructions for protein synthesis  Introns: intervening, non-coding nucleotide sequences

13. mRNA Splicing:  Spliceosomes: Cut out the introns and join the exons together  mRNA molecule is formed and is now ready to leave the nucleus

14. Page: 249  Questions 1, 2, 3, 5, 9