https://www.khanacademy.org/science/ms-biology/x0c5bb03129646fd6:inheritance-and-variation/x0c5bb03129646fd6:mutations/a/mutations 2024-06-28T21:00:15.59562973Z Mutations Learn about beneficial, neutral, and harmful genetic mutations. article https://www.khanacademy.org/science/health-and-medicine/executive-systems-of-the-brain/neurodevelopmental-disorders/a/what-is-down-syndrome 2021-04-29T08:03:34Z What is Down syndrome? article https://www.khanacademy.org/science/biology/classical-genetics/sex-linkage-non-nuclear-chromosomal-mutations/a/x-inactivation 2021-08-02T05:22:02.009586435Z X-inactivation How XX human females (and other female mammals) shut down one of their X chromosomes in each cell. Disorders of sex chromosome number: Klinefelter, triple X, and Turner syndromes. article