Chapter 11 Flashcards
DNA replication: short ds region of DNA with a 3’ hydroxy end serves as the primer, DNA polymerase reads the template strand, and a new complimentary strand is formed
RNA transcription: RNA polymerase reads the template DNA strand, and makes a new mRNA strand that is complimentary to the template DNA and identical to the coding DNA
Semi conservative: helix has one strand comprised of old DNA and one new strand of DNA
Conservative: one helix formed contains old DNA, one helix formed contains all new DNA
E. Coli grown in a N15 rich environment, labeled with heavy, dense N15. After replication over one generation, all N14/N15 labeled Hybrid DNA, after 2 generations, all N14 and N14/N15 hybrid DNA. The presence of hybrid DNA after replications proved that DNA replication is semi conservative
Major grooves: more open parts of DNA, allows more substances in to bind
Minor grooves:less open parts of DNA
Helical and propellor twists
Syn conformation: base and sugar are positioned directly in line with each other, favored due to methylation of cytosine making the methyl group hydrophobic, and high salinity
Anti conformation: base and sugar positioned 180 degrees apart
B DNA: right handed helix, 10 base pairs per turn, most commonly depicted form of DNA favored in solution, heavily stabilized by water hydrogen bonding in major grooves
A DNA: right handed helix 11 base pairs per turn, shorter and broader DNA, favored in dehydrated environments due to DNA compressing to account for water loss.
Z DNA: left handed helix, phosphate backbone in a Zig Zag formation, long narrow DNA, 12 base pairs per turn, favored in environments with high salinity due to cations of salt interacting with the phosphate backbone making it neutral and closer together
Factors that Favor -H: hydrogen bonds although individually weak present in large number making H more negative, pi-pi stacking 16-51 kj/mol present in large number making H more negative.
Thermodynamics: negative G driven by negative H despite negative S
Intercalating agents are short, flat, planar aromatic rings that insert into the major grooves of DNA and disrupt pi-pi stacking. This causes DNA to become partially unwound disrupting the double helix structure
The desaturation of DNA at absorbance 260 nm
DNA can be denatured by: temperature (dependent on G:C content), pH(<2.3 bases are protonated, >10 bases are deprotonates), salinity (higher salinity = higher Tm), and H- bonding organics
Thermodynamics: as electrons get excited move from low energy to high energy orbital, disrupting pi-pi stacking causing DNA to be denatured
Melting curve shows absorbance (y axis) versus melting temperature (x axis)
The midpoint is dependent on the Tm, which is reliant of the G:C content
