1. Bellwork: What are the main differences between RNA and DNA

2. RNA
Section 3.1

3. What is RNA? Another type of nucleic acid A working copy of DNA
Does not matter if it is damaged or destroyed
Used to direct the production of proteins that determines an organisms characteristics

4. What are the differences between RNA and DNA?
There are 3 key differences
1) sugar is Ribose rather than De- oxy ribose
2) RNA is generally single stranded
3) RNA contains Uracil rather than Thymine
Chemical differences make it easier for a cell to distinguish between RNA and DNA

5. Functions of RNA Main function – protein synthesis 3 types of RNA
Controls assembly of amino acids into proteins
3 types of RNA
Messenger RNA
Carry information from the DNA to other parts of the cell
Ribosomal RNA
Ribosomes are made of ribosomal RNA and proteins
Transfer RNA
Transfers amino acids to the ribosome as/when they are needed

6. RNA synthesis Transcription Prokaryotes Eukaryotes
Segments of DNA serve as template to produce complementary RNA molecules
Prokaryotes
RNA synthesis and Protein synthesis occurs in the cytoplasm
Eukaryotes
RNA produced in the nucleus
Transcription occurs in the cytoplasm
The enzyme RNA polymerase controls transcription
One gene can produce hundreds or thousands of RNA molecules

7. Promoters
RNA polymerase will only bind to areas of DNA where a promoter is present
Promoter = region of RNA that has specific base sequences
Similar signals cause transcription to stop

8. RNA editing
RNA needs a bit of tweaking before it can be put into action
Chunks are cut out of them and discarded – introns
In eukaryotes, introns are taken out of pre-mRNA molecules whilst they are in the nucleus
What is left – exons, are spliced back together to form the final mRNA

9. Why does RNA polymerase make more than it needs?
Scientists still aren’t sure
Some pre-mRNA molecules may be cut/spliced in different ways in different tissues – so a single gene can produce several forms of RNA
Intron and Exons may play a role in evolution
Small changes in DNA sequences can have a large effect on how genes affect cellular function

10. Summary RNA is a working copy of the DNA
Made from small sections of DNA (transcription)
RNA polymerase
Promoters indicate which part of DNA to use
Three key types of RNA
Messenger
Ribosomal
Transfer
More is made than needed
Introns discarded
Exons kept