Q- Presence of nucleus is essential for maintenance and working of the cells, so nucleus is commonly called “Director of the cell”. Answer the following questions?
(i) Give the term for the cells having incipient nucleus.
(ii) Name two cell types having no nucleus.
(iii) Name various part of a nucleus and state one function of each of them.
Answer- (i) Prokaryotic cells is the the term for the cells having incipient nucleus.
(ii) Tracheids and vessels of xylem of plants and Mammalian RBCs are the two cell types having no nucleus.
(iii) The nucleus is mainly composed of four main parts. These parts name with their functions are as follows:
1. Nuclear membrane: It is the outer most layer or membrane of the nucleus.
Function of nuclear membrane:
Regular exchange of materials between nucleoplasm and cytoplasm.
2. Nucleoplasm: It is the fluid present inside the nucleus.
Function of Nucleoplasm:
It act as skeleton of the nucleus and is involved in formation of spindle proteins.
Function of Nucleolus:
Nucleolus helps in formation of r-RNAs. It is also responsible for the storage of these r-RNAs.
4. Nuclear chromatin (Chromosomes):
Chromosomes are the genetic material in the nucleus.
Function of Nuclear chromatin (Chromosomes):
Nuclear chromatin (Chromosomes) contain genetic material (DNA) which helps in heredity and variations. The main function of DNA in chromosomes is to inherit the basic characters from parents to their offspring.