Gene Expression I pp. 204-206
Overview The first step to making proteins is called transcription DNA RNA Protein
Location Prokaryote: Cytoplasm Eukaryote: Nucleus
Transcription DNA RNA Protein DNA is “rewritten” into mRNA Only genes needed for specific proteins are transcribed
Transcription RNA Polymerase binds to DNA DNA unzips
RNA Polymerase adds complementary RNA Nucleotides RNA has Uracil (U) instead of Thymine (T) Guanine and Cytosine are the same
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
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.
Result of Transcription Produces a single strand of mRNA mRNA then carries “instructions” to ribosomes in the cytoplasm to make proteins