Viswanathan K's Thoughts

DNA strands are long (several meters long). How on earth do they then fit inside the nucleus of a cell? By bending and folding themselves. But not in any random way. They wrap themselves around proteins 10 nanometers in size called histones . But it would require a lot of force to compress them like this. What is the source of that much force? The answer is electrostatic force, between the negatively charged DNA and the positively charged histone.   This isn’t just “intellectual curiosity”. Which parts of the DNA are “expressed” as proteins depends on the packaging and wrapping of the DNA. How? Remember DNA strands are read by a transcription molecule called RNA. Parts of the DNA that are inaccessible (due to the way they are wrapped) won’t be expressed. It has thus been turned “off”! Accessible = On; inaccessible = Off. “The physical arrangement of DNA is a powerful tool for regulating the activities of the cell.” writes Raghuveer Parthasarathy in So Simple a Beginning . ...

You thought we carried genes from both our parents, right? That’s only partially true. As most of us know, we have 23 pairs of chromosomes that are indeed the mix of genes from both our parents. Apart from that, as Siddhartha Mukherjee explains in his masterpiece, The Gene , there’s also the mitochondria within which each cell that has its own set of genes that has nothing in common with the rest of our genes! Further, the genes of the mitochondria come only from the mother . Now consider the full implication of this. Or if you can’t, let Mukherjee explain it for you. The genes in your mitochondria are identical to those in your mother, who in turn got them from her mother and so on… it’s only women all the way up the mitochondrial chain. Or to put it differently, a male is a dead end as far as the transmission of the mitochondria gene set is concerned. Now comes the best part: A world-wide survey (across races and countries) of the human mitochondrial DNA in 1987 yielded a ...