Question

Which one of the following occurs in meiosis but NOT in mitosis?

1) crossing-over
2) disintegration of the nuclear envelope
3) cells remain diploid
4) spindle fibers attach to centromeres
5) sister chromatids separate

Answer 1

Crossing-over is a unique event that occurs during Prophase I of meiosis and is not present in mitosis, leading to increased genetic diversity in the resulting gametes.

Step-by-step explanation:

The event that occurs in meiosis but NOT in mitosis is crossing-over. During Prophase I of meiosis I, homologous chromosomes pair up and exchange genetic material, a process known as crossing-over. This process contributes to genetic diversity. Unlike meiosis, mitosis does not involve pairing of homologous chromosomes, hence no crossing-over occurs. Other options, such as the disintegration of the nuclear envelope, spindle fibers attaching to centromeres, and the separation of sister chromatids, occur during both mitosis and meiosis at various stages. However, cells remaining diploid is characteristic of mitosis, not meiosis, where the goal is to produce haploid gametes.