Barr Body Explained: X-Chromosome Inactivation Made Simple

Barr Body Explained: X-Chromosome Inactivation Made Simple

Question 1. Barr body.
Answer:

• The inactivation of an X-chromosome forms sex – chromatin also called barr body.
• It can be seen in the nuclei of somatic cells in the female only.

Barr body Appearance:

• Chromatin mass lying against the inner surface of the nuclear membrane
• Or as a small drumstick’ of chromatin projecting from then nuclei of the polymorphonuclear leucocytes.

Question 2. Karyotyping.
Answer:

• Individual chromosomes differ from one another in the following aspects.
  1. Total length of chromosome.
  2. Relative length of the two arms.
  3. Various other characteristics.
• These differences enables us to identity the individual chromosome.
• Classification of chromosome in this way is called karyotyping.

Question 3. Sex chromosome
Answer:

• Sex chromosome may be of two kinds
• X and Y
• In males there are 44 autosomes and one X and one Y chromosome
• Similarly females has 44 autosomes and two X chromosomes
• Thus in any individual, 22 pair of autosomes and one pair of sex chromosome is present
• One chromosome of each pair is derived from mother and other from father