Sister chromatids fail to separate during meiosis II. What fraction of the resulting gametes is normal?

1. Meiosis I has already separated the homologues correctly, so both daughter cells start out normal. 2. The error happens later, when sister chromatids fail to separate in one of those two cells. 3. That affected cell produces one gamete with two copies and one gamete with none. 4. The unaffected cell divides normally and produces two gametes with one copy each. 5. Counting the four gametes gives one with two copies, one with none, and two normal. 6. Two out of four normal is one half. 7. A meiosis I failure, by contrast, leaves no normal gametes at all. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 13 "Modern Understandings of Inheritance", section 13.2 Chromosomal Basis of Inherited Disorders_