Nucleus: at a glance

Nucleus 

Parts of nucleus

•      Nuclear membrane

•      Nucleolus

•      Chromatin &  nucleoplasm

Nuclear membrane

•      It is a double layer membrane. The outer layer of membrane attached with ribosomes and continuous with rER.

•      Pores present 

Nucleolus:  

1. It is a structure found in the nucleus of cells.

2. It is formed by proteins and nucleic acids. 

3. It is occupies about 25% of the volume of the cell nucleus.

Function:

 It transcribes ribosomal RNA (rRNA)

The synthesis of RNA is regulated by five different chromosomes (13, 14, 15, 21, and 22). 

 Malfunction of nucleoli : 

mutation causes malfunction  of nucleus and it is related to following disease like Weine syndrome, Treacher Collins Syndrome and dyskeratosis.

      Chromatin / Chromatin granule- 

        The readily stainable substance of a non dividing cell nucleus consisting of DNA and RNA and various     

            proteins; during mitotic division it condenses into chromosomes

•      They are two types: 

Heterochromatic

Densely packed portion of chromatin which is genetically inactive.

Bluish in colour. 

Euchromatic
 uncoiled portion of chromatin which is genetically active.
 Lightly stain 

What is chromosome?

•      it is  a  threadlike structures, which visible during cell division and is composed by

•      DNA,

•      Small RNA,

•       histone and non-histone protein. (consisting of genes that are responsible for the transmission of hereditary characteristics)

Types of chromosome:

 Autosomes chromosome:

•      The genes which regulate body character.

•      They are 22 pairs

 Sex chromosome: 

•      The genes which regulate sex character.

•      They are 1 pair

•      In male one X and one Y .

                  XY

•      In female two X.  

                        XX

Chromosomes number in human body

•      46

•      /23 pairs

•       22 pairs autosomes + 1pair sex chromosome

Diploid: A cell or an organism consisting of two sets of chromosomes:

Usually, one set from the mother and another set from the father.

In a diploid state, the haploid number is doubled, thus,

This condition is also known as 2n.

Haploid: The number of chromosomes in a gamete of an organism, symbolized by n. 

Parts of a chromosome

Each chromosome has a constriction point called the centromere, which divides the chromosome into two sections, or “arms.”

 The short arm of the chromosome is labeled the “p arm.”

The long arm of the chromosome is labeled the “q arm.

Chromatid - one of two identical strands into which a chromosome splits during mitosis