How can nondisjunction of the x chromasomes lead to Klinefelters and Turners syndrome?
Okay, first nondisjunction refers to the failure of chromosomes to separate correctly during meiosis or mitosis. When in the situation of Klinefelter’s or Turner’s, the incorrect separation of chromosomes happens during meiosis and happens to the sex determining chromosomes. Okay, here we go: For an example, let’s keep it simple and just look at the two sex chromosomes. We’ll go with female, who is XX. For the sake of keeping track, we’ll label them Xx instead. When the cell is getting ready for meiosis, the two chromosomes make an exact copy of themselves called sister chromatids (let’s say we now have an XX and a xx in the same cell). Normally during meiosis I, they should separate the chromosomes into two cells, but keeping the identical sisters together: Cell A: XX Cell B: xx During meiosis II, Cell A will separate it’s sister chromatids, and Cell B will do the same. We should wind up with four cells: Cell C: X Cell D: X Cell E: x Cell F: x Klinefelters can occur if during Meiosis
