Question

Describe the ultrastructure of eukaryotic chromosomes.

Answer 1

Eukaryotic chromosomes:

1. Eukaryotic chromosomes consist of a DNA-protein complex arranged in a compact manner that allows large amounts of DNA to be stored in the nucleus of the cell.
2. The subunit designation of chromosomes is chromatin.
3. The basic unit of chromatin is the nucleosome.

Ultrastructure of eukaryotic chromosomes:

1. A metaphase chromosome is ideal for studying chromosome structure as it becomes thicker and shorter due to compaction.
2. A chromosome in metaphase is composed of 2 longitudinally identical units called chromatids that are located together at a common point called the centromere.
3. Under a light microscope, a metaphase chromosome shows the centromere representing the primary constriction and deeply stained regions called arms.
4. Electron microscopy studies reveal the presence of two arms connected by centromeric regions.
5. The ends of the chromatids are telomeres.
6. Some chromosomes also have secondary contractions.