Summary on Transcription

Vocab:  Coding strand = Sense
            Template = Antisense
            Upstream = Promoter Region = TATA box
            Downstream = Terminator Region = AAUAA ... box?
            pre-mRNA = RNA Transcript

1)  Find the TATA box sequence on the DNA.  The It should read from 3' to 5' (on the DNA) because all RNA and DNA code from 5' to 3'.  The TATA box is also known as the 'promoter region' or 'upstream'.

2)  TFs (transcription factor) find the TATA boxes and act as a 'beacon' for Polymerase II to bind to.  TFs are made of proteins.

3)  Polymerase II attaches to the TFs.

4)  TATA box, TF, and Polymerase II put together is known as the Initiation Process.

5)  Polymerase II elongates the pre-mRNA from 5' to 3'.  The RNA transcript is similar to the Coding Strand.

6)  When AAUAA is reached on RNA, coding of the RNA is finished.

7)  G-capping of the 5' end and poly (A) tail caps the 3' end to protect the RNA Transcript.  Poly (A) tail adds 50-250 adenine nucleotides.

8)  DNA Splicing occurs to fix any mutations and get rid of any unnecessary coding.  Spliceosomes are made of snRNPs and snRNAs.  snRNAs recognize the beginning and end of intron and help the spliceosome to attach to the RNA Transcript.  The snRNP part of the spliceosome brings the intron into a loop (to increase stability and decrease mutations) and severs the intron away from the exon.  The severed intron is not useless; sometimes becomes TFs.  The intron is the unwanted code.  the exon is the needed code.

9) Transcription is complete; the pre-mRNA / Transcript RNA is now a mRNA.

Steps 1-4 is known as Initiation, step 5 is known as Elongation, and steps 6-8 is known as Terimnator.

Note:  pre-mRNA is always found in nucleus.  Is only released into the cell's cytoplasm when it has undergone safeguarding by DNA splicing and capping.