Final answer:
There are four levels of chromosome condensation: wrapping around histone proteins, coiling into a 30-nm chromatin fiber, packing with fibrous proteins, and condensation during prophase.
Step-by-step explanation:
In eukaryotic cells, chromosomes undergo condensation during certain stages of the cell cycle to fit inside the cell's nucleus. There are four levels of chromosome condensation:
Level 1: Short stretches of DNA wrap around histone proteins to form nucleosomes, which are about 10 nm in diameter.
Level 2: Nucleosomes and the linker DNA between them coil into a 30-nm chromatin fiber, further compacting the chromosome.
Level 3: Fibrous proteins are used to pack the chromatin and ensure each chromosome occupies a specific area of the nucleus.
Level 4: Chromosomes condense even further during prophase of the cell cycle, becoming visible under a microscope.