AP BIOLOGY

Detailed explanation-1: -In 1903, Nikolai K. Koltsov proposed that the shape of cells was determined by a network of tubules that he termed the cytoskeleton.

Detailed explanation-2: -Their major discovery was x-ray crystallography, which showed that MreB had the actin fold and was assembled in the crystals into actin-like filaments. Later work has discovered multiple prokaryotic actins with a variety of cytoskeletal functions, although the functions of most are unknown.

Detailed explanation-3: -The eukaryotic cytoskeleton evolved from prokaryotic cytomotive filaments. Prokaryotic filament systems show bewildering structural and dynamic complexity and, in many aspects, prefigure the self-organizing properties of the eukaryotic cytoskeleton.

Detailed explanation-4: -In 1963, improved fixation methods led to the definitive identification of microtubules (see “Microtubules get a name” JCB. 168:852). Just one year later, Gary Borisy embarked on a daring project to isolate the main component of those microtubules. The effort was initiated by Edwin Taylor at the University of Chicago.