What is X chromosome inactivation?
The process by which the expression of X-linked genes is balanced between males and females
The process by which a gene's expression is regulated by the number of copies of the gene in the genome
The process by which the X chromosome is replicated during the cell cycle
The process by which a gene is mutated and loses its normal function
The process by which one of the two X chromosomes in female cells is randomly inactivated early in embryonic development is known as X chromosome inactivation. The inactivated X chromosome condenses and forms a unique structure in the nucleus known as a Barr body, whereas the active X chromosome remains uncondensed and is responsible for X-linked gene expression in that cell. Because males only have one X chromosome and females have two, this process ensures that the dosage of X-linked genes is equalised between sexes. To ensure that the next generation has an equal chance of inactivating either X chromosome, the inactivated X chromosome is reactivated in cells that give rise to eggs or sperm.
Option 1 is the correct answer.