Transcription Turning DNA into RNA

Promoter Region Promoter sites: locations on DNA just before the gene Transcription factors (proteins) bind at promoter sites RNA polymerase (enzyme) binds to the transcription factors Together, these open the DNA (unzip)‏

Copying Copying DNA to form RNA is transcription RNA polymerase reads one side of the DNA molecule RNA nucleotides are assembled following rules for base pairing to make a molecule of RNA  A in DNA matches with U in RNA  T in DNA matches with A in RNA  C matches with G

Completion of Transcription When the transcription factor reaches a stop codon, it detaches Polymerase is released from DNA and transcription stops Different kinds of RNA are formed this way:  mRNA: messenger, which carries the message out of the nucleus  rRNA: ribosomal, which makes ribosomes  tRNA: transfer, which moves amino acids around

RNA Processing Prokaryotes: not necessary

RNA Processing Eukaryotes: mRNA breaks into pieces Pre-mRNA detaches from polymerase with a modified guanine attached (the cap)‏ Introns removed step by step  Most begin with GU and end with AG  Spliceosomes work to cut out introns and splice exons Exons reattached into one strand of mRNA Poly-A tail added to mRNA strand to complete the mRNA molecule

Completed mRNA Now the mRNA leaves the nucleus Source: rna_polymerases

Animation of Transcription class.unl.edu/biochem/gp2/m_biology/animation /gene/gene_a2.html class.unl.edu/biochem/gp2/m_biology/animation /gene/gene_a2.html