Which chromosome shows a greater number of bands: prophase or metaphase chromosome? Why?

The prophase chromosome shows a greater number of bands as compared to the metaphase chromosome. When chromosomes are stained using banding techniques like G-banding (Giemsa banding), we observe alternating light and dark regions on chromosomes. These bands are very helpful in studying the structure of chromosomes and in identifying chromosomal abnormalities. In the prophase stage of mitosis, the chromosomes begin to condense, but they are still in a relatively loose or extended form. Due to this less compact structure, the staining can reveal more bands with higher resolution. Therefore, prophase chromosomes show a greater number of distinct bands.

In comparison, metaphase chromosomes are more tightly packed and highly condensed. This makes the individual bands merge together or become less visible. As a result, the number of visible bands in metaphase is lower than in prophase.

So, the answer is that prophase chromosomes show more bands than metaphase chromosomes.

Reason for the Difference in Number of Bands

The difference in band number is mainly due to the degree of chromatin condensation. In prophase, chromatin fibres start condensing, but the process is not complete. Because of this, individual DNA regions are more accessible to staining dyes. This partial condensation allows the dyes to bind to smaller regions, resulting in high-resolution banding patterns. With high-resolution prophase banding, scientists can see more than 1000 bands across all chromosomes in a diploid human cell.

On the other hand, in metaphase, the chromosomes are fully condensed. The tight coiling brings many adjacent DNA segments close together, making it difficult to distinguish between individual regions. As a result, the banding pattern becomes broader, and fine details are lost. In metaphase chromosomes, usually about 300 to 400 bands can be observed in a haploid set.

Therefore, although the DNA content of a chromosome does not change between prophase and metaphase, the visible banding pattern depends on how tightly the chromatin is coiled. The less condensed chromatin in prophase shows more bands, while the highly condensed chromatin in metaphase shows fewer bands.

This property is widely used in cytogenetics to detect small deletions or duplications. High-resolution prophase banding allows scientists to detect subtle chromosomal abnormalities that might not be visible at metaphase level.







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