Features of male-specific portion of Y chromosome A pachytene chromosome-based cytogenetic mapping of male-specific portion of Y chromosome

Features of male-specific portion of Y chromosome
A pachytene chromosome-based cytogenetic mapping of male-specific portion of Y chromosome (MSY) was done to study the features of MSY portion. The MSY portion spans 13% portion of the Y chromosome. Centromere is present within MSY portion. A high amount of methylation was also detected in MSY portion. Both centromere and methylation has an important role in silencing of genes, heterochromatinization and suppression of recombination in evolution of Y chromosome (Zhang et al., 2008).
Evolution of X and Y chromosomes
Expansion of Y chromosome (Yu et al., 2008a) and X chromosome (Gschwend et al., 2012) is the most common characteristics during early stages of sex chromosomes (X and Y) evolution. A comparison of the recently originated papaya X chromosome was done to its homologous autosome in close relative monoecious Vasconcellea monoica to predict the evolutionary history of X chromosome. The genome size of V. monoica (626 Mb) was found 41% larger than the papaya genome (372 Mb). This result suggested that papaya X chromosome is expanded due to higher accumulation of repetitive sequences.