Final answer:
Option (B), In the earliest karyotypes, chromosomes were distinguished by general size classes. Banding patterns were visualized using stains like Giemsa, which helped in detailed chromosome identification for karyotypes.
Step-by-step explanation:
In the earliest karyotypes, chromosomes were distinguished by general size classes. Chromosomes were identified based on characteristics such as number, size, centromere position, and later by banding patterns using staining techniques like Giemsa stain. Geneticists would stain chromosomes, revealing about 400-800 bands which allowed detailed identification of each chromosome pair's characteristic banding pattern.
To construct a karyotype, cytologists first photographed chromosomes during cell division. They then meticulously arranged the pictures into a chart, or karyogram, organizing them from longest to shortest based on size and according to their centromere locations. This process resulted in a visual representation crucial for assessing chromosomal abnormalities.