All cytokines have a similar tertiary structure consisting of four long conserved α helices folded together.

TLS Online TPP Program

#Id: 2998

#Unit 3. Fundamental Processes

On the leading strand (sometimes called the forward strand) DNA synthesis can proceed continuously in the 5 ' to 3’ direction as the parental duplex is unwound.

TLS Online TPP Program

#Id: 3005

#Unit 3. Fundamental Processes

On the lagging strand a stretch of single-stranded parental DNA must beexposed, and then a segment is synthesized in the reverse direction (relative to fork movement).

TLS Online TPP Program

#Id: 3006

#Unit 3. Fundamental Processes

These Okazaki fragments are found in replicating DNA in both prokaryotes and eukaryotes.

TLS Online TPP Program

#Id: 3007

#Unit 3. Fundamental Processes

The lagging strand is synthesized discontinuously and the leading strand is synthesized continuously. This is called semidiscontinuous replication.

TLS Online TPP Program

#Id: 3008

#Unit 3. Fundamental Processes

That not all of the fragment population represents bona fide Okazaki fragments; some are pseudo fragments that have been generated by breakage in a DNA strand that actually was synthesized as a continuous chain. The source of this breakage is the incorporation of some uracil into DNA in place of thymine. When the uracil is removed by a repair system, the leading strand has breaks until a thymine is inserted. 

TLS Online TPP Program

#Id: 3009

#Unit 3. Fundamental Processes

Replication requires a helicase to separate the strands of DNA using energy provided by hydrolysis of ATP.