Watch the human genome fold itself in four dimensions:
By removing and then adding this protein, called cohesin, researchers made specific DNA loops that disappear and then reappear, they report this month in Cell. But cohesin really only affects looping that brings genes on the same chromosome into contact. A second, still-undefined mechanism seems to bring genes from different chromosomes together, the team notes.
Will we ever… reveal all the secrets of life from DNA?:
Our metaphors let us down. Science writers like to compare the genome to a textbook or a blueprint. That conveys the fact that it stores information, but glosses over its buzzing, dynamic nature – proteins docking on and off to control the activity of genes, huge stretches of DNA that fold and unfold to reveal or hide their sequences,,, jumping genes that copy themselves and hop throughout the genome… None of our information stores – not sheet music, not recipe books – are this intricate.More. (BBC 2012)
Genes and Organisms: Improvising the Dance of Life:
Excerpt: packing DNA into a typical cell nucleus is like packing about 24 miles of very thin, double-stranded string into a tennis ball, with the string cut up (in the normal human case) into 46 pieces, corresponding to our 46 chromosomes.
To locate a protein-coding gene of typical size within all that DNA is like homing in on a one-half-inch stretch within those 24 miles. Or, rather, two relevant half-inch stretches located on different pieces of string, since we typically have two copies of any given gene. Except that sometimes one copy differs from the other and one version is not supposed to be expressed, or one version needs to be expressed more than the other, or the product of one needs to be modified relative to the other. So part of the job may be to distinguish one of those half-inch stretches from the other. …
the cell, by managing the shifting patterns of the chromatin infrastructure within which DNA is embedded, brings our chromosomes into movement on widely varying scales. These include large looping movements that put particular genes into connection with essential regulatory sequences and with other, related genes (that is, with other one-half inch stretches of our “24 miles of string in a tennis ball”). …
… There is no neatly predefined path to follow once the cell has located the “right” half inch or so of string, or once it has done whatever is necessary to bring that locus into proper relation with other chromosomal loci participating in the same “dance”. … the overall picture of gene expression is one of unsurveyable complexity in the service of remarkably effective living processes. …
A decisive problem for the classical view of DNA is that “as cells differentiate and respond to stimuli in the human body, over one million different proteins are likely to be produced from less than 25,000 genes”.30 Functionally, in other words, you might say that we have over a million genes. … (Stephen L. Talbott, Nov. 10, 2015)
Hat tip: Philip Cunningham