In of meiosis, homologous chromosomes pair
up, crossing-over occurs, nuclear envelope breaks down, and a
spindle begins to form.

Prophase I

Explanation:

In prophase I, each pair of homologous chromosomes (one chromosome from each parent) lines up side by side. This aligning of homologous chromosomes is called synapsis. At synapsis, the homologous chromosomes are held tightly together

along their lengths. While they are lined up, segments of the chromosomes may be exchanged. This process of exchange of genetic information is an important mechanism for providing genetic diversity, and is discussed later in this section. As prophase I continues, the centrosomes move to the poles of the cell and the spindle apparatus forms.

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