When the DNA is replicating bidirectionally, that means the DNA is replicating in two directions from the starting point at the same time resulting in the formation of two strands i-e leading and lagging.
Leading strands undergoes rapid replication while the lagging strand undergoes slow replication and forms okazaki fragments.
As DNA is replicating in two directions from the starting point, two replication forks (area where DNA replication occurs actively) are formed both moving in opposite direction.
Hence option D) Replication froks is the right answer.
As DNA helicase unwinds the DNA using ATP, the relief of supercoil needs topo-isomerase. Helicases move on both directions, separating the strand in advance of the replication. This forms a replication bubble with two replication forks.
Each replication fork contains DNA helicase which unwinds a short region of DNA helix.
The replication fork looks like a fork in the road that is composed of a leading strand and a lagging strand of DNA.
The process of muscle contraction requires several steps.
The most famous theory on how the contraction and relaxation of muscles take place is the sliding filament theory.
However, this theory has been refined and one important addition to it is the mechanism by which myosin can pull actin and cause shortening of the sarcomere.
For the movement of myosin, it binds and releases actin and forms cross bridges.
Myosin is subdivided into two regions - S1 and S2. The contraction of the S1 region is what constitutes the power stroke.
An important requirement of the power stroke is the hydrolysis of ATP to release an inorganic phosphate which provides energy for the process.
