Question

Barr body is associated with
(a)Y-chromosome
(b)X-chromosome
(c)Autosome
(d)Male sex only

Answer 1

Hint: This chromosome is present in both the parents but is different in numbers. It consists of around 900 to 1400 genes translated from around 155 million base pairs that carry 5 % of total DNA in their cell. Hemophilia or bleeder’s disease is associated with this chromosome.

Complete answer:
Barr bodies are the inactive form of X-chromosome present in the cell having one or more than one X-chromosomes. They are found mostly in the sex determination of XY-type which includes humans.

Additional Information:
-The X-chromosome is a sex-determining chromosome, also called as allosome.
-It is found in both male and female individuals.
-It is present along with its counterpart Y-chromosome on male individuals.
-In females, two X-chromosomes are present while in males only one X-chromosome is found.
-The pattern of X-chromosome inheritance is criss-cross, where the male parent will inherit X-chromosome to female offspring which is then inherited to the male offspring.
-The disease which occurs due to the mutation on X-chromosomes is known as X-linked disease.
-The X-chromosome is larger than the Y-chromosome and has more euchromatin regions.
-The increase or decrease in the normal number of X-chromosome in an individual will result in an abnormality.
-X-chromosomes are said to be associated with the development of intelligence.
-The Y-chromosome is responsible for maleness in an individual while X-chromosome is responsible for femaleness.
-Few examples of X-linked recessive disorders are hemophilia, color-blindness, muscular dystrophy, etc.

So, the correct answer is, “X-chromosome.”

Note: The Barr body was discovered in 1938 by a Canadian physician Murray Barr. This occurs due to the inactivation of the X-chromosome due to the process of Ionization (packed in an inactive structure called heterochromatin). Its most common example is of Klinefelter syndrome having 47+XXY chromosomal composition with a single Barr body and if the composition is 47+XXX then there will be two Barr bodies.