The contributions of Nettie Stevens to the field of sex chromosome biology

Abstract

The early 1900s delivered many foundational discoveries in genetics, including re-discovery of Mendel's research and the chromosomal theory of inheritance. Following these insights, many focused their research on whether the development of separate sexes had a chromosomal basis or if instead it was caused by environmental factors. It is Dr Nettie M. Stevens' Studies in spermatogenesis (1905) that provided the unequivocal evidence that the inheritance of the Y chromosome initiated male development in mealworms. This result established that sex is indeed a Mendelian trait with a genetic basis and that the sex chromosomes play a critical role. In Part II of Studies in spermatogenesis (1906), an XY pair was identified in dozens of additional species, further validating the function of sex chromosomes. Since this formative work, a wealth of studies in animals and plants have examined the genetic basis of sex. The goal of this review is to shine a light again on Stevens’ Studies in spermatogenesis and the lasting impact of this work. We additionally focus on key findings in plant systems over the last century and open questions that are best answered, as in Stevens' work, by synthesizing across many systems. This article is part of the theme issue ‘Sex determination and sex chromosome evolution in land plants’.

Young evolutionary origins of dioecy in the genus Asparagus

“…However, approximately 6% of angiosperm species evolved separate sexes (dioecy) producing strictly pistillate or staminate flowers, functioning as either female or male individuals, respectively (Renner, 2014). Interestingly, dioecy has independently evolved numerous times in ancestrally hermaphroditic clades across the angiosperm phylogeny (Ming et al, 2011; Carey et al, 2022). Theory suggests that dioecy is adaptive in that it precludes inbreeding through self‐pollination (Charlesworth and Charlesworth, 1978; Thomson and Barrett, 1981) and can improve fertility through focused resource allocation for production of pollen (males) or ovules and seeds (females) (Darwin, 1877; Barrett, 1992; Ramsey et al, 2006).…”

Museu virtual de Ciências: uma breve história das principais descobertas genéticas

“…A bióloga e geneticista americana Nettie Maria Stevens (Figura 19) descobriu os cromossomos sexuais X e Y e sua importâncias nas características sexuais dos seres vivos (Carey, Aközbek, Harkess, 2022). Posteriormente, em 1961, a geneticista inglesa Mary Frances Lyon descobriu a inativação de um dos cromossomos X (Lyon, 1961), que foi já havia sido batizado como corpúsculo de Barr ou cromatina sexual pelo médico canadense Murray Llewellyn Barr em 1949(Barr, Bertram, 1949.…”