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Question
Role of chromosomes in sex determination was proposed by
Role of chromosomes in sex determination was proposed by
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Solution
The correct option is C Mc Clung
The first inkling that sex chromosomes were unique from all other chromosomes came from experiments conducted by German biologist Hermann Henking in 1891. Henking saw that some wasp sperm cells had 12 chromosomes, while others had only 11. Moreover, while observing the stages of meiosis that formed these sperm cells, Henking noticed that the mysterious twelfth chromosome looked different from all the others. He thus named this chromosome the "X element," to represent its unknown nature.C. E. McClung began extensive research into the idea that the X element must have something to do with sex determination. First, McClung asserted that this strange chromosome be called the "accessory chromosome," because it appeared to have a separate purpose compared to the other chromosomes. Next, he decided to undertake a wide comparative study of spermatogenesis not just in insects but in many different organisms, including spiders and mice. While observing sperm generation in grasshoppers, McClung noted that the accessory chromosome did not behave as the other chromosomes did during the first meiotic division. Specifically, this "twelfth chromosome" was not distributed equally to the four sperm cells that arose from one grasshopper spermatogonium; instead, it was present in only half of them. This consistent pattern of segregation in the spermatogenesis of many different organisms caused McClung to speculate that there must be some fundamental reason for the generation of two types of sperm cells. McClung thought about the consequences of this 50/50 distribution of the accessory chromosome, and he pondered how this distribution probably resulted in two different kinds of zygotes. He also noted that there was really only one characteristic that varied among zygotes of many different species in 50/50 proportions, and that characteristic was sex. Thus, when he assembled all the evidence together, McClung came up with the proposal that the accessory chromosome must influence the determination of sex in a zygote.
So, the correct answer is 'Mc Clung'.
The first inkling that sex chromosomes were unique from all other chromosomes came from experiments conducted by German biologist Hermann Henking in 1891. Henking saw that some wasp sperm cells had 12 chromosomes, while others had only 11. Moreover, while observing the stages of meiosis that formed these sperm cells, Henking noticed that the mysterious twelfth chromosome looked different from all the others. He thus named this chromosome the "X element," to represent its unknown nature.
C. E. McClung began extensive research into the idea that the X element must have something to do with sex determination. First, McClung asserted that this strange chromosome be called the "accessory chromosome," because it appeared to have a separate purpose compared to the other chromosomes. Next, he decided to undertake a wide comparative study of spermatogenesis not just in insects but in many different organisms, including spiders and mice. While observing sperm generation in grasshoppers, McClung noted that the accessory chromosome did not behave as the other chromosomes did during the first meiotic division. Specifically, this "twelfth chromosome" was not distributed equally to the four sperm cells that arose from one grasshopper spermatogonium; instead, it was present in only half of them. This consistent pattern of segregation in the spermatogenesis of many different organisms caused McClung to speculate that there must be some fundamental reason for the generation of two types of sperm cells. McClung thought about the consequences of this 50/50 distribution of the accessory chromosome, and he pondered how this distribution probably resulted in two different kinds of zygotes. He also noted that there was really only one characteristic that varied among zygotes of many different species in 50/50 proportions, and that characteristic was sex. Thus, when he assembled all the evidence together, McClung came up with the proposal that the accessory chromosome must influence the determination of sex in a zygote.
So, the correct answer is 'Mc Clung'.
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