Chromosomes Need to be Condensed and Moved
- Human DNA stretches over 50,000 μm but must fit into a nucleus less than 5 μm wide.
- Without condensation, DNA would tangle or break during cell division.
Imagine trying to pack a 50-meter rope into a 5-centimeter box.
Histones Drive DNA Condensation Through Supercoiling
- Histones are proteins that act as spools around which DNA wraps, forming nucleosomes, the first level of condensation.
- Nucleosomes coil into a thicker fiber called chromatin, which further coils and folds into highly condensed chromosomes visible during cell division.
- This process is called supercoiling.
- Chromatin is the less condensed form of DNA present during interphase.
- Chromosomes are the highly condensed form visible only during cell division.
Microtubules and Motor Proteins Move Chromosomes
Once condensed, chromosomes must be precisely moved to ensure each daughter cell receives the correct genetic material.
- The Structure
- Microtubules are hollow tubes made of tubulin subunits that extend from opposite poles to form the spindle apparatus.
- Kinetochores are protein complexes at the centromere where microtubules attach to chromosomes.
