The Gene: An Intimate History by Siddhartha Mukherjee

The Gene: An Intimate History by Siddhartha Mukherjee

Author:Siddhartha Mukherjee [Mukherjee, Siddhartha]
Language: eng
Format: epub
Publisher: Scribner
Published: 2016-05-17T07:00:00+00:00

What is a gene, then? When Mendel discovered the “gene” in 1865, he knew it only as an abstract phenomenon: a discrete determinant, transmitted intact across generations, that specified a single visible property or phenotype, such as flower color or seed texture in peas. Morgan and Muller deepened this understanding by demonstrating that genes were physical—material—structures carried on chromosomes. Avery advanced this understanding of genes by identifying the chemical form of that material: genetic information was carried in DNA. Watson, Crick, Wilkins, and Franklin solved its molecular structure as a double helix, with two paired, complementary strands.

In the 1930s, Beadle and Tatum solved the mechanism of gene action by discovering that a gene “worked” by specifying the structure of a protein. Brenner and Jacob identified a messenger intermediate—an RNA copy—that is required for the translation of genetic information into a protein. Monod and Jacob added to the dynamic conception of genes by demonstrating that genes can be turned on and off by increasing or decreasing this RNA message, using regulatory switches appended to each gene.

The comprehensive sequencing of the worm genome extended and modified these insights on the concept of a gene. A gene specifies a function in an organism, yes—but a single gene can specify more than a single function. A gene need not provide instructions to build a protein: it can be used to encode RNA alone, and no proteins. It need not be a contiguous piece of DNA: it can be split into parts. It has regulatory sequences appended to it, but these sequences need not be immediately adjacent to a gene.

Already, comprehensive genome sequencing had opened the door to an unexplored universe in organismal biology. Like an infinitely recursive encyclopedia—whose entry under encyclopedia has to be updated constantly—the sequencing of a genome had shifted our conception of genes, and therefore, of the genome itself.


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