TLS Online TPP Program

#Id: 2342


The consensus sequence reflects preferred –10 and –35 regions, separated by the optimum spacing (17 bp).


#Unit 3. Fundamental Processes #Elongation #Part B Pointers
More Pointers
TLS Online TPP Program

#Id: 3986

#Unit 2. Cellular Organization

Addition of a topoisomerase greatly facilitates nucleosome association with cccDNA.
When a topoisomerase is present during nucleosome assembly, it cannot act on the DNA bound to the nucleosome. Instead, the topoisomerase relaxes the DNA not included in nucleosomes, reducing the positive superhelical density in these regions by decreasing the linking number.

TLS Online TPP Program

#Id: 3988

#Unit 2. Cellular Organization

By maintaining the unbound DNA in a relaxed state, topoisomerases facilitate the binding of histones to the DNA and the formation of additional nucleosomes.
Importantly, the overall effect on the plasmid is that the linking number is decreased as more nucleosomes are assembled

TLS Online TPP Program

#Id: 3990

#Unit 2. Cellular Organization


TLS Online TPP Program

#Id: 3992

#Unit 2. Cellular Organization

Because nucleosomal DNA wraps around the histone protein 1.65 times, the formation of a single nucleosome using ccc plasmid would create a writhe of –1.65 and thus change the linking number by an equivalent amount. As described above, when the change in linking number associated with each nucleosome was measured, the number was lower than this, approximately –1.2 for each nucleosome added.
This discrepancy is referred to as the “nucleosome linking  number paradox,”

TLS Online TPP Program

#Id: 3993

#Unit 2. Cellular Organization

TLS Online TPP Program

#Id: 3995

#Unit 2. Cellular Organization

When an ethidium ion intercalates between two base pairs, it causes the DNA to unwind by 260, reducing the normal rotation per base pair from 360 to 100. In other words, ethidium decreases the twist of DNA.