Nucleus

Question 1 Who discovered nucleus?

Question 2 What is the location of nucleus?

Question 3 Explain the structure of nucleus?

Question 4 Differentiate between  Prokaryotic Cell and Eukaryotic cell?

Question 5 What are chromosomes made of?

Question 6 Give the characteristics of different types of chromosome?

Question 7 What is a diploid cell?

Question 8 What is a haploid cell?

Nucleus

We can use iodine,Safranin or methylene blue to stain the cell.Different regions of cells gets coloured differently due to different chemical composition.

Nucleus is centrally located spherical cellular component.It has a double layer covering called cellular nuclear membrane.

Nuclear membrane has space between them which are connected to a system of membranes called ER.It separates nucleus from cytoplasm.It contains many pores called nucleus pores and encloses a liquid substance(nucleoplasm).The pores allow the transfer of material from inside the nucleus to its outside.

Nucleus contain

1)Nucleons:It may be one or two in number,not bounded by any membrane,rich in proteins and RNA,site of ribosome formation.

2)Chromatin Material:It is thin,thread like intertwined mass of chromosome material and composed of genetic substance like DNA and protein.

DNA contains information for construction and organising cells.

Functional segment of DNA are called genes.

Whenever the cell is about to divide,the chromatin material gets organised into chromosome.

Chromosomes are thread like structure usually present in the nucleus and become visible only during cell division.They contain heredity information of cell in the form of genes.

Metacentric Chromosome

1)They are V shape.
2)Arms are almost equal.
3)Centromere is near the middle.

Submetacentric chromosomes

1)One arm is slightly short than other.
2)They are J shape.
3)Centromere is slightly away from middle point.

Acrocentric chromosomes

1)One arm is very short and other is very long.

2)They are rod shaped.

3)Centromere is near the end.

Telocentric chromosomes
1)Centromere is at the tip.
2)Arms are on one side only.
3)They are rod shaped.

Human being have 46 chromosomes(44 autosomes+2 Sex chromosomes).The paired condition of chromosome is called as diploid.
A cell which has full number chromosome is called Diploid cell.
A Cell comprising of unpaired chromosome of each kind is haploid.

Functions of Nucleus
1)It plays a central role in cellular reproduction.
2)It regulates cell cycle.

Prokaryotic Cell	Eukaryotic Cell
1) Size of cell is small	Size of cell is large
2) Nucleus is absent	Nucleus is present
3) It contains single chromosomes	It contains more than one chromosomes.
4) Nucleolus is absent	Nucleolus is present.
5) Mitochondria,Plastids,ER,Golgi apparatus,Lysosomes etc are absent.	Mitochondria,Plastids,ER,Golgi apparatus,Lysosomes etc are Present.
6)Cell division take place by fission.	Mitotic or meiotic cell division occurs.