After obtaining her Ph.D. After obtaining the grant, she employed germ cells of aphids to study possible differences in chromosome sets concerning the two sexes. She focused her doctoral research on matters this kind of as regeneration in primitive multicellular organisms, the framework of one celled organisms, the enhancement of sperm and eggs, germ cells of insects, and cell division in sea urchins and worms. He performed cytological examination only on the testes, that is he did not take a look at the female germ cells (eggs) but only the male germ cells (sperm) in his experiments. When the sperm with the massive chromosome fertilized eggs, they manufactured feminine offspring, and when the sperm with the little chromosome fertilized eggs, they manufactured male offspring. An egg fertilized by a sperm that carries the smaller chromosome turns into a male while an egg fertilized by a sperm with the larger sized chromosome will become female. Her discovery was the to start with time that observable distinctions of chromosomes could be linked to an observable distinction in phenotype or actual physical characteristics (i.e., irrespective of whether an particular person is male or woman). Using observations of insect chromosomes, Stevens found that, in some species, chromosomes are distinctive in between the sexes and when chromosome segregation takes place in sperm formation, this variance sales opportunities to results of woman vs . male progeny.

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