Recall what you learned about the fate of homologous chromosomes during meiosis I and the sister chromatids during meiosis II, and explain how trisomies like trisomy 21 or poly-X syndrome could occur

Please look in the explanation section

Explanation:

During meiosis I, pairing of homologous chromosomes occurs, resulting in the exchange of chromatids. Subsequently, homologous chromosomes separate between each other resulting in a decrease in the number of chromosomes. In meiosis II it occurs that the sister chromatids separate, each of the chromosomes formed by separating two different cells. Down syndrome occurs when in the process of abnormal cell division it helps with added genetic material on chromosome 21. On the other hand, poly x syndrome is a genetic disorder that occurs in women, leading to the formation of three X chromosomes. instead of two only two chromosomes.

the dark variety, as they are not visible on the dark tree barks

explanation:

the diploid number of chromosomes is sometimes represented by the symbol 2n. for the fruit fly, the diploid number is 8, which can be written as 2n = 8, where n represents twice the number of chromosomes in a sperm or egg cell.