DNA Transcription

Initiation: 

Initiation complex:
-Transcription factors recognize and locate the TATA box
-TATA box is the promoter region

• RNA polymerase II unwinds and opens a section of the double helix
• RNA polymerase II binds to the promoter region 
• RNA transcription begins in the coding strand of DNA with RNA polymerase II

Elongation:

• RNA pol II synthesizes a strand of mRNA (complimentary to template strand)
• "T"is replaced with "U" in the mRNA strand
• RNA pol II works in the direction of 5' to 3'
• mRNA is anti parallel with the DNA Template strand (Antisense), and is similar to the DNA Coding strand (Sense)
• transcription goes from upstream (promoter) to downstream (terminator)

Termination:

• Transcription stops and RNA pol II detaches from the DNA strand when it reaches the "AAA UAA" signal
• pre-mRNA becomes RNA by the addition of a G-cap to the 5' end and the addition of a 3'poly-A tail to the 3' end
• Intron sections of the mRNA are cut out by the spliceosome and the Exons are joined together 
• Spliceosome are assembled from snRNP which are proteins that contain snRNA who recognize the Intron segements

Quote of the Day #1

"Science and everyday life cannot and should not be separated." -Rosalind Franklin

The 3 Acts of DNA Replication

Initiation:

• Helicase unwinds and separates DNA (at the point of origin)
• Binding proteins bind to keep the DNA strands apart and unwound
• Gyrase enzyme cuts the DNA to release the tension
• Primase makes an RNA primer which the DNA polymerase III uses to begin replicating the new strands

Elongation:

• Polymerase III adds nucleotides to the 3' of the new strand
• DNA's anti parallel structure results in the new strands growing in opposite directions
• Leading vs Lagging strands:
•  the leading strand replicates continuously
•  the lagging strand replicates discontinuously
•  RNA primase synthesis RNA primer
•  Polymerase III extends the strand by adding new nucleotides to the 3' end
•  a new DNA fragment is generated from the end of each primer
•  the DNA fragments are called Okazaki fragments
•  Polymerase I removes RNA primer and fills the gap by extending the neighbouring DNA
•  Okazaki fragments are joined by DNA Ligase

Termination:

• Newly formed strands rewind
• Replication machine dismantles as the new DNA molecules separate from each other and the DNA replication is complete