PROBLEM: How does the chromosome condense from 4 cm (average length of DNA assuming all chromosomes in people have the same amount of DNA...NOT!) to 4 x 10-4 cm (average length of chromosome assuming all chromosomes in people are the same length ....NOT!)?
| Compaction Ratio(length) | Width | Mechanism |
| 1 | ~25A | DNA stretched |
| 1/2.5 | 50A | Produced by wrapping the DNA around the nucleosome core; the wrapping is around a basic core particle composed of dimers of histones H2A, H2B, H3 and H4..H1 exist between the units and probably has a primary role in the condensation of the units. |
| 1/7 | 100A | The entire structure undergoes a right hand rotation of 40 degrees to produce an A fiber... it exists in the absence of divalent cations. |
| 1/50 | 250A (2.5x 10-6 cm) | The unit formed is called a B fiber or Dupraw fiber and is formed by minisolenoids. This is a packaging in regular arrays |
| 1/1000 | 4000A | Supersolenoids held together by protein DNA linkers. This forms a unit known as a domain.At this point we are to a chromosome about the size of that observed in meiotic or mitotic prophase. |
| 1/10,000 | 4 x 10-4cm | The final step is SUPERCOILING to form a metaphase chromosome...or an extremely compacted chromosome modified for division. |
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