Lyonisation is a process in which one of the two copies of X chromosomes in female body becomes inactivated. This prevents from making two copies of the product of X chromosomal genes as those of the males which has only single copy of X chromosome called dosage compensation. The X chromosome is silenced and made transcriptionally inactive called heterochromatic body. This process is proposed by Mary Lyon and Liane Russell.

What is called pedigree analysis?

A pedigree is a genetic representation of a family tree that shows the occurrence and appearance of phenotypes of a particular gene or organism and its ancestors from one generation to the next. It shows the relationships between family members and indicates which individual expresses or silently carries the trait in question. In a simpler way, pedigree analysis shows the inheritance of genes in humans. Relationships in a pedigree chart are shown as a series of lines. A horizontal line connects parents, and a vertical line connects their offspring. Squares represent males, and circles represent females. A person with unknown gender is represented by a diamond shape. A person with the phenotype in question is represented by a darker (filled-in) symbol. Heterozygotes are indicated by a shaded dot inside a symbol or a half-filled symbol.