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.

Lampbrush chromosomes http://www.le.ac.uk/biology/staff/hcm4.html

Oocyte transcription http://www.acs.ucalgary.ca/~browder/oogen2.html

Salivary gland chromosomes http://sdb.bio.purdue.edu/fly/aimorph/puffing.htm

LAST TWO LECTURES

We expanded on the concepts of nuclear

equivalency, genomic equivalency, nuclear and DNA constancy and totipotency.

You are expected to be familiar with COT curves...see

http://www.cc.ndsu.nodak.edu/instruct/mcclean/plsc431/eukarychrom/eukaryo3.htm

You are also expected to understand how the development of B (and T) cells results

in a deviation from DNA constancy. see your text: pp. 409-415

Some info on Hn RNA: http://testzygote.swarthmore.edu/rna1.html

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.