Concept 29 DNA is packaged in a chromosome.
The Kornberg family, Stockholm, 1959. (L-R) Roger, Kenneth, Sylvy, Arthur, Thomas.
Roger Kornberg in his laboratory, 1970s.
Aaron Klug at a Cold Spring Harbor meeting.
Roger Kornberg, 1980s.
Aaron Klug at a Cold Spring Harbor meeting.
Dean Hewish, 1973.
Leigh Burgoyne, 1973.
Photo of chromatin digested by nuclease, from Hewish and Burgoyne's 1973 experiment.
Electron micrograph of the 10-nm fiber.
Electron micrograph of the 30-nm fiber.
Electron micrograph of the DNA and the protein scaffold left over from one chromosome (insert) with all the histone stripped out.
Although prokaryotes do not have a nucleus and do not package their DNA as chromatin, there does seem to be some organization to their DNA. This suggests that prokaryotes have proteins that can act like histones.
Why did such a system evolve for packaging DNA? Wouldn't it work just as well if the DNA weren't coiled but were laid out in parallel strands like in a fiber optic cable?
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The Kornberg family, Stockholm, 1959. (L-R) Roger, Kenneth, Sylvy, Arthur, Thomas.
DNA is packaged in a chromosome.
Higher cells incorporate an ancient chromosome.
Some DNA does not encode protein.
Some DNA can jump.
Genes can be turned on and off.
Genes can be moved between species.
DNA responds to signals from outside the cell.
Different genes are active in different kinds of cells.
Master genes control basic body plans.
Development balances cell growth and death.
A genome is an entire set of genes.
Living things share common genes.
DNA is only the beginning for understanding the human genome.