Question

A well defined nucleus is absent in
A. Prokaryotic cell
B. Eukaryotic cell
C. Animal cell
D. Plant cell

Answer 1

Hint: A well-defined nucleus is referred to the nucleus that consists of the nuclear material enclosed within a nuclear membrane. It is generally a characteristic of cells belonging to non-primitive organisms. However, primitive organisms (such as bacteria) often lack a well-defined nucleus within their cell.

Complete answer:
A primitive cell that lacks a well-defined nucleus is primarily referred to as a prokaryotic cell. Hence, the genetic material (or nuclear material) is suspended freely in the cytoplasm of the prokaryotic cells. In addition to this, the prokaryotic cells do not have other membrane-bound cell organelles. Bacteria, mycoplasma, and blue green algae are a few examples of prokaryotes lacking a well-defined nucleus within their cells.
A cell containing well-defined nucleus and other membrane bound cell organelles are commonly called eukaryotic cells. These are the non-primitive or advanced cells having complex structure as well as their functioning. The plant cell and animal cell are examples of the eukaryotic cells as both cells contain well-defined nucleus and membrane bound cell organelles. Animal cells generally lack a cell wall, however a plant cell has a cell wall made up of cellular.

The correct answer is option A, prokaryotic cell.

Note:
 In eukaryotic cells of plants and animals, the nuclear material (DNA) is wrapped within a nucleus and is surrounded by a membrane called nuclear membrane. There are numerous pores present on this nuclear membrane. Various cell organelles such as mitochondria, endoplasmic reticulum, Golgi bodies, and others are present within the cell cytoplasm.