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Sex Chromosome Pairing and Fertility in the Heterogametic Sex of Mammals and Birds
Published in Christopher B. Gillies, Fertility and Chromosome Pairing: Recent Studies in Plants and Animals, 2020
The special condensation of the sex chromosomes during male meiosis has been known for a long time.7 This condensation is widespread, but not universal, during meiosis in the heterogametic sex.7 Sachs5 assumed that this condensation was needed for the restriction of recombination between the X and Y chromosomes. Furthermore, Lifschytz and Lindsley21 presented the hypothesis that the inactivation of the X chromosome, as shown in the XY condsensed body, was a requisite for the development of spermatogenesis. From these functional considerations, some mechanisms have been assumed to involve sex-chromosome pairing and infertility (see Section VIII).
J.B.S. Haldane (1892–1964)
Published in Krishna Dronamraju, A Century of Geneticists, 2018
Haldane’s first publications in 1912, however, were in physiology, not genetics. He was a polymath whose scientific work covered physiology, genetics, biochemistry, biometry, statistics, cosmology, and philosophy, among other disciplines. After serving in World War I (1915–1919), Haldane resumed his investigations of linkage, devising the first mapping function and suggesting the measure of chromosome map distance, centimorgan or cM (Haldane 1919), which was later adopted by molecular biologists. Shortly afterward, in 1922, Haldane proposed the generalization concerning the offspring of interspecific crosses, which was termed “Haldane’s rule”: “When in the first generation between hybrids between two species, one sex is absent, rare, or sterile, that sex is always the heterogametic sex” or, as he put it, “that is to say, the sex which produces two sorts of gametes, namely the male in most animal groups, the female in birds and Lepidoptera” (Haldane 1922).
Gender-Specific Disease
Published in Mary Ann G. Cutter, The Ethics of Gender-Specific Disease, 2012
In twentieth-century medicine, identification of sex has come to be based on certain key biological factors such as genital structure (e.g., clitoris, penis), hormonal make-up (e.g., estrogen, progesterone, testosterone), and genetic (chromosomal) patterns (e.g., XX for females, XY for males) (Hyde and Whipple 2005, 173–74). With the rise of genetic knowledge, the chromosomal description of sex has come to dominate clinical discussions today. The “XY sex-determination system,” as it is called, is found in humans, most other mammals, some insects (Drosophila), and some plants (Ginkgo), In this system, females have two of the same kind of sex chromosome (XX), and are called the “homogametic” sex. Males have two distinct sex chromosomes (XY), and are called the “heterogametic” sex. The XY sex-determination system was first described independently by Nettie Stevens and Edmund Beecher Wilson in 1905 (Kingsland 2007), and since then, molecular biologists have explored a more subtle dosage of genes that interplay with each other rather than function as a simple linear pathway in which genes determine sex.
Cellular mechanisms regulating synthetic sex ratio distortion in the Anopheles gambiae germline
Published in Pathogens and Global Health, 2020
Roya Elaine Haghighat-Khah, Atashi Sharma, Mariana Reis Wunderlich, Giulia Morselli, Louise Anna Marston, Christopher Bamikole, Ann Hall, Nace Kranjc, Chrysanthi Taxiarchi, Igor Sharakhov, Roberto Galizi
Like in humans, Anopheles males are the heterogametic sex carrying both heteromorphic sex chromosomes (XY), whilst females are homogametic (XX). Thus, the genetic engineering of such synthetic sex distorters can be achieved by selectively disrupting the viability of the male gametes carrying the X chromosomes making only Y-bearing sperm available to fertilize the wild-type females’ oocytes [4,5]. One way to achieve this goal is to use endonucleases to target repetitive sequences uniquely present within the X chromosome during male meiosis (the process driving the formation of the haploid gametes). This strategy is generally identified as ‘X-shredding’.