Question

Amitosis is
A. Division involving formation of chromosome bridges
B. Division involving spindle formation
C. Division in which chromosomes are unequally distributed
D. Cleavage of nucleus without recognizable chromosome distribution

Answer 1

Hint: Cell division occurs by three methods - amitosis, mitosis and meiosis. In each method, division of the nucleus called karyokinesis occurs before the division of the cytoplasm termed as cytokinesis. Amitosis was first discovered by Remak in 1841 in the red blood cells of chick embryos and later described by Flemming.

Complete answer: It has a very simple mechanism. It occurs without the formation of spindle and appearance of chromosomes. The nuclear envelope remains intact. Amitosis is often called direct division.
The nucleus of the cell elongates and develops a constriction round its middle. The constriction gradually deepens and cuts the nucleus into two daughter nuclei.
A similar constriction appears in the cytoplasm between the two daughter nuclei and divides the parent cell into two daughter cells each with a nucleus. The daughter cells receive approximately equal amounts of nuclear and cytoplasmic materials.
Mitosis is rare and probably because it is not an exact method of cell division. It takes place in certain specialized cells such as those in the mammalian cartilage, in the growing embryonic membranes of some vertebrates, in the degenerating cells of higher plants, in the diseased tissues and in the old tissues. The macronucleus of ciliates such as Paramoecium divides by amitosis. Some authors regard bacterial cell division as amitosis because no spindle is formed in it.
So, the correct answer is “Option D”.

Note: Cell division is a means of multiplication in the unicellular organisms. In multicellular organisms, it brings about embryonic development and growth and also plays a role in repair and maintenance of the body and also in reproduction, both sexual and asexual.