1. Chapter 13: RNA and Protein Synthesis
Section 13-1: RNA

2. The Role of RNA
The sequence of bases in DNA carries a code – but what does it mean?
DNA contains instructions telling the cell how to make proteins
First step to is copy part of the DNA sequence into RNA (ribonucleic acid), which then directs the production of proteins

3. Comparing RNA and DNA
RNA is also a chain of nucleotides, each containing a 5 carbon sugar, phosphate group, and nitrogenous base
But there are 3 differences, which allow cellular enzymes to tell them apart:
Sugar in RNA is ribose
RNA is single-stranded
RNA contains uracil in place of thymine

4. Comparing RNA and DNA
DNA is like the “master plan” and RNA is the “blueprints”
DNA stays in the nucleus, while RNA go to the protein-builders in the cytoplasm - ribosomes

5. Functions of RNA
RNA is a disposable copy of a segment of DNA, the working copy of a single gene
It has many functions, but most RNA molecules are involved only in protein synthesis
Controls the assembly of amino acids into proteins
There are three types of RNA specializing in each aspect of this job

6. Messenger RNA Carry copies of genes (instructions for proteins)
Carry information from DNA in the nucleus to other parts of the cell
Abbreviated mRNA

7. Ribosomal RNA
Proteins are assembled at ribosomes, which are made of two subunits
The subunits are made of several molecules of ribosomal RNA (rRNA) and up to 80 different proteins

8. Transfer RNA
Transfers amino acids to the ribosome according the code specified by mRNA
Abbreviated tRNA

9. Transcription The process of making mRNA from a DNA template
The mRNA is complementary to a template segment of DNA
In prokaryotes, RNA synthesis and protein synthesis both take place in the cytoplasm
In eukaryotes, RNA is synthesized in the nucleus then moves into the cytoplasm

10. Transcription - Eukaryotes
Requires enzyme RNA polymerase, which binds to DNA during transcription and separates the strands
It then uses one of the DNA strands as a template to assemble a complementary RNA strand

12. Promoters
RNA polymerase only binds to promoters, which are regions of DNA with specific base sequences
They are signals within the DNA molecule that tell RNA polymerase where to start making RNA
There are similar signals in DNA that tell RNA polymerase when to stop transcription

13. RNA Editing
Before RNA molecules become active, sometimes bits and pieces have to be cut out
The pieces that are cut out and discarded are called introns
In eukaryotes, introns are removed from pre-mRNA before it leaves the nucleus
The remaining pieces – called exons – are spliced back together to form the final mRNA

15. RNA Editing
Biologists don’t fully understand why cells make a large RNA molecule and then throw parts of that molecule away
Some pre-mRNA molecules can be cut and spliced in different ways in different tissues
Introns and exons may also play a role in evolution – small changes in DNA sequences can cause dramatic effects

16. Animations!