The Amami spiny rat (Tokudaia osimensis) lacks a Y chromosome, yet scientists at Hokkaido University in Japan have reported that key sex-determining genes continue to be expressed in this species. Provide possible explanations for why male differentiation can still occur in this mammalian species despite the absence of a Y chromosome.

Video transcript

Hello everyone. Let's look at our next question. It says male sex in humans is determined by the Y. Chromosome in which the following species does the Y chromosome not determine gender. Let's note that we have a choice of D. All of the above. So all of our answer choices could be correct. So choice is the fruit fly. And in the fruit fly the Y chromosome does not determine gender. The fruit fly, it's the X chromosome to autism ratio That determines gender. So if that ratio is 1-1, the fruit fly will be female. Two X chromosomes to autism's. At that ratio is one half to one that equals a male phenotype. So fruit flies will just mark here again because we do have a choice of all the above. Um The Y chromosome does not determine gender choice. B. Is the mommy spiny rat. And this is very unusual in that although it's a placental mammal, it has no Y chromosome. So in humans and other placental mammals that Y chromosome has a gene called S. R. Y. And that S. R. Y. Gene turns on other genes that um cause male sex determination. The Emami spiny rat has no Y. Chromosome and therefore no um no S. R. Y. Gene. But another gene, another unknown gene appears to turn on the sex determining genes so that that part of the pathway still exists. It's just not regulated by the Y. Chromosome. So we don't know exactly what they are yet but they do not depend on the Y chromosome. So that's another correct answer choice enjoy sea grasshopper. The grasshopper also doesn't depend on the Y chromosome. It has an X. X. X. O. Pattern for determining sex, so Xx female XO mail. There is no Y chromosome there. So grasshopper also doesn't depend on that Y chromosome. So our correct answer choice there is choice D. So which of these animals? Does the Y chromosome not determined gender choice D. All of the above referring to the fruit fly, the Amami, spiny rat and the grasshopper. See you in the next video.