Final answer:
Stopping mitosis at metaphase is beneficial for karyotyping because chromosomes are maximally condensed and neatly arranged at the metaphase plate, providing a clear and distinguishable view for each chromosome.
Step-by-step explanation:
The advantage of stopping mitosis at metaphase when making a chromosome spread is that during metaphase, the chromosomes are maximally condensed and aligned at the metaphase plate, which is located roughly midway between the two pole ends of the cell. This arrangement allows for a clear visual of each individual chromosome, facilitating the process of karyotyping. When cells in metaphase are burst under pressure, the chromosomes spread out and can easily be stained, displaying distinct morphological variations along their lengths for observation and analysis.
Metaphase chromosomes are advantageous to study because they have already replicated into sister chromatids and are tightly attached at the centromere, yet highly accessible since they are lined up on the metaphase plate. Moreover, the microtubules, important for later stages of mitosis, do not impede the viewing of chromosomes, which are isolated from each other and do not overlap significantly, thanks to the spatial organization rendered by the metaphase arrangement.