Question

ii) Why do all gametes formed in human females have an X chromosomes?

Answer 1

humans have 23 sets of chromosomes, out of which 22 are autosomes which are all similar shaped, while the last one pair is the sex chromosome which determines the sex of an individual. For females these sex chromosomes are shaped like XX while in male they are roughly shaped as XY. Thus you can see that female can only contribute X chromosome in either situation, where as the whole possibility or probability depends on the chromosome or the pair contributed by male! You hv the image attached below. You can see how the X chromosoje is given by females and how they fuse with the make chromosomes. When the X from females fuse with X of make then it forms an individual of XX chromosome which is a girl (female) but when the X from female fuses with the Y then it forms the XY individual which is a male. So this is how we determine the sex. And through this mechanism there are 50% chances if getting male or female.

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