Final Answer:
During prophase, chromosomes condense and become visible. Each chromosome has two halves called sister chromatids. Each sister chromatid of a chromosome is genetically identical, resulting from DNA replication. The chromosomes remain in the nucleus during prophase, and the nuclear envelope disintegrates after prophase, allowing further progression of mitosis or meiosis.
Step-by-step explanation:
During prophase, chromosomes condense and become visible as distinct structures under a microscope. Each chromosome consists of two identical halves called sister chromatids, connected by a centromere.
The sister chromatids are genetically identical as they result from DNA replication during the previous S phase. These chromatids are held together by cohesion proteins. The chromosomes remain within the nucleus during prophase, undergoing further condensation and structural changes. The nuclear envelope disintegrates, allowing microtubules to extend from the centrosomes toward the chromosomes.
The microtubules will play a crucial role in the subsequent stages of mitosis. Prophase marks the initiation of mitosis or meiosis, setting the stage for the orderly distribution of genetic material during cell division.