Speciation and the large effect of sex chromosomes

Biologists have long suspected that the origin of species can be a result of differential evolution and adaptation between populations. Yet generalities about the phenotypes or underlying genes responsible for speciation remain broadly unresolved. Despite this uncertainty, the disproportionate role of sex chromosomes in speciation is well recognized. Two routes of investigation into speciation have […]

Restricting X|Y Recombination

In this post, I review the evolution of recombination rate between the sex chromosomes. As considered in a previous post, low rates, and more often absence, of crossover between parts of the X and the Y plays an important role in sex chromosome evolution and is frequently considered a defining characteristic of sex chromosomes. Wide variation […]

Why the X and Y don’t match

Because X-Y heteromorphism allowed for the sex chromosomes to be followed through meiotic division, it was the first marker to be correlated with the segregation and inheritance of a phenotype (sex). Still today, molecular differences between X and Y are used to identify the sex chromosomes in genetic sequencing studies. Because of its pivotal role […]

Early Studies in Sex Chromosome Evolution

The discovery of sex chromosomes, at the turn of the twentieth century, significantly shaped not only how we study sex chromosomes today but also the fields of genetics and evolution more broadly. The first heteromorphic chromosomes to be correlated with sex phenotypes were observed in insects. In 1905, cytological study led N. Stevens to find […]