The birth of a male sex chromosome in Atlantic herring

The evolution of sex chromosomes is of crucial importance in biology as it stabilizes the mechanism underlying sex determination and usually results in an equal sex ratio. An international team of scientists, led by researchers ...

Why the 'wimpy' Y chromosome hasn't evolved out of existence

Much smaller than its counterpart, the X chromosome, the Y chromosome has shrunken drastically over 200 million years of evolution. Even those who study it have used the word "wimpy" to describe it, and yet it continues to ...

When determining sex, exceptions are the rule

For nearly a century, biologists have modeled the evolution of sex chromosomes—the genetic instructions that primarily determine whether an individual will develop into a male or female (or a certain mating type)—resulting ...

The surprising structure of a shrub willow sex chromosome

Sex in plants can be befuddling. Most species are hermaphrodites, expressing both male and female gametes in one individual. But some, including shrub willow Salix purpurea, employ the evolutionary strategy we are far more ...

Record-size sex chromosome found in two bird species

Researchers in Sweden and the UK have discovered the largest known avian sex chromosome. The giant chromosome was created when four chromosomes fused together into one, and has been found in two species of lark.

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