1. KEY CONCEPT Transcription is the process of converting the DNA’s code for one gene into an RNA strand.

2. DNA has the code but RNA carries DNA’s instructions to the ribosomes
DNA must remain “safe” in the nucleus while RNA can leave to carry the gene’s code to the ribosome

3. RNA: Ribonucleic Acid
RNA differs from DNA in three major ways.
(1) RNA is a single-stranded molecule.
(2) RNA has a ribose sugar as its 5-carbon sugar
(3) RNA has uracil instead of thymine.

4. Transcription copies DNA’s code to make a strand of RNA
Why?
Make an expendable copy to send out of the nucleus
DNA can stay safe in nucleus
When?
At the start of Protein Synthesis
Where?
In the nucleus

5. How?
(1) An enzyme recognizes the start of a gene and “unzips” the weak hydrogen bonds in DNA.
start site
nucleotides
transcription complex

6. RNA polymerase moves along the DNA
(2) Free-floating RNA nucleotides attach to the left strand of the DNA, forming hydrogen bonds. (nucleotide=sugar+phosphate+base)
DNA
RNA polymerase moves along the DNA

7. Covalent bonds are created.
RNA pulls away from the DNA and the DNA strands “zip” back up.
RNA