Transcription

• Uracil


  Demethylated thymine
• To get an mRNA transcript, you take DNA, then hydroxylate the 2' carbon of the deoxyribose, and demethylate the thymines to get uracil
• RNA polymerase II

  Uses DNA to make a complementary strand of RNA, which becomes the mRNA transcript
• Processing

  Made up of protection and splicing, what happens to mRNA before it can leave the nucleus and make it to the ribosomes
• Protection


  Part of mRNA processing where the 5' end of a G nucleotide is attached to the 5' end, and a bunch of A nucleotides are attached to the 3' end to stop the mRNA from degrading when exposed to enzymes in the cytoplasm
• Poly A tail


  Bunch of adenine nucleotides attached to the 3' end of an mRNA strand so that it doesn't get degraded by enzymes in the cytoplasm
• Exonuclease


  Enzyme in the cytoplasm that attacks mRNA with exposed 5' ends that hasn't gone through processing
• Introns


  Sequences of RNA that don't contain any instructions for building proteins which are removed during splicing
• Splicing


  Part of processing involving removing the introns so that only primary mRNA coding for proteins leaves the nucleus
• Spliceosome


  Complex of enzymes that cuts out introns and fuses the remaining parts of the mRNA transcript back together
• Primary mRNA


  Intron-free mRNA transcript that the spliceosome produces
• Pre mRNA


  Original version of an mRNA transcript before its been spliced at the spliceosome
• Initiation


  Stage 1 of transcription
• Elongation


  Stage 2 of transcription
• Termination


  Stage 3 of transcription
• Initiation


  RNA polymerase belongs to the promoter on the DNA strand, found near the beginning of a gene. Once bound, it separates the strands, creating a replication bubble with two single strand templates necessary
• Elongation


  RNA polymerase reads the template strand one base at a time, adding a new nucleotide in the 5' - 3' direction. Transcript has same info as the coding strand, just U instead of T
• Coding strand


  DNA strand that isn't getting read by RNA polymerase, but ends up being the same as the RNA strand made from the template strand (complimentary to the template strand)
• Termination


  Terminator sequences signal that the RNA transcript is complete, and transcription ends.
• Transcription happens individually for each gene, which lets your cell express what it has to express given the conditions
• Alternative splicing


  When more than one protein can be synthesized from one gene, depending on how it's spliced