Go to Adv Bio Trimester 1 SIZE Magnified in the light microscope, the rod-like chromosomes within one cell vary considerably in size. This is NOT a karyotype because it only shows a chromatid pair joined at the centromere for each chromosome number. A karyotype shows each homologous pair for each chromosome number. To view a karyotype, click here .
Many chromosomes have clear constrictions in their rods.
The primary constrictions are called centromeres. The ends are called telomeres. Metacentric chromosomes have their centromere near the center of the chromosome. Submetacentric chromosomes have slightly off-center centromeres, such that one chromosome arm is longer than the other. Staining results in crosswise patterns of bands that are characteristic of that chromosome.