Question

What is meant by incipient nucleus?

Answer 1

The bacterial cells have a freely floating genetic material in an irregular shape. This genetic material is present in the undefined irregular region called the nucleoid. All the prokaryotes carry such a nucleus which is termed as the incipient nucleus. This kind of nucleus cannot undergo meiosis.

Complete answer: Prokaryotic organisms are considered ancient and primitive organisms having the simplest cellular organization. Prokaryotic cells are those that do not contain a defined membrane-bound organelle called the nucleus. The nucleus generally is the membrane-bound organelle found in eukaryotes, which encloses the cell’s genetic material. Prokaryotes lack a nucleus. They have a specialized irregular undefined region in their cytoplasm in which the genetic material floats. This region is called the incipient nucleus. It is also called nucleoid or naked nucleus as it contains no membrane and no definite shape.

Histone proteins that bind to chromosomes to form the chromatin fibre are absent in bacterial chromosomes. Due to this, chromosomes lie freely as thread-like structures floating in the cytoplasm. The incipient nucleus is also called the initial state of the nucleus as it is the primitive form of the nucleus which developed into a proper nucleus in later eukaryotic cells with the higher cellular organization. Nucleoid is formed by functional arrangement and condensation along with supercoiling of the bacterial DNA. The chromosomes are circular in prokaryotes and have very large dimensions as compared to the cell. Thus, the chromosome needs to be highly coiled in order to fit inside the cell.

Note: Exposures to DNA damaging situations can cause changes in the structure of the nucleoid or incipient nucleus. It is observed in E.coli that its nucleoid becomes more compact when subjected to UV radiations. Compaction of nucleoid has been thought to be a DNA damage response that helps in locating damaged regions and start their repair.