1. Gene Expression I pp

2. Overview The first step to making proteins is called transcription
DNA  RNA  Protein

3. Location
Prokaryote: Cytoplasm
Eukaryote: Nucleus

4. Transcription DNA  RNA  Protein DNA is “rewritten” into mRNA
Only genes needed for specific proteins are transcribed

5. Transcription
RNA Polymerase binds to DNA
DNA unzips

6. RNA Polymerase adds complementary RNA Nucleotides
RNA has Uracil (U) instead of Thymine (T)
Guanine and Cytosine are the same

7. Polymerase falls off & DNA rebinds
EXAMPLE:
Polymerase falls off & DNA rebinds
DNA Strand
A G T C G T C G A T C A
T C A G C A G C T A G T
mRNA Strand
A G U C G U C G A U C A

9. RNA Processing
The genomes of eukaryotes are larger and more complex than those of prokaryotes.
Eukaryotic genes are organized into noncoding sections (introns) and coding sections (exons).
In eukaryotes the transcription product is first called pre-mRNA
After transcription the introns are cut out from pre-mRNA to make mRNA.

10. Result of Transcription
Produces a single strand of mRNA
mRNA then carries “instructions” to ribosomes in the cytoplasm to make proteins