Aunque no es inmortal, el tiburón boreal Somniosus microcephalus sigue siendo un animal impresionante y está mucho más emparentado con nosotros. Es c… - David A. Sinclair

The longevity genes I work on are called "sirtuins," named after the yeast SIR2 gene, the first one to be discovered. There are seven sirtuins in mammals, SIRT1 to SIRT7, and they are made by almost every cell in the body. When I started my research, sirtuins were barely on the scientific radar. Now this family of genes is at the forefront of medical research and drug development. Descended from gene B in M. superstes, sirtuins are enzymes that remove acetyl tags from histones and other proteins and, by doing so, change the packaging of the DNA, turning genes off and on when needed. These critical epigenetic regulators sit at the very top of cellular control systems, controlling our reproduction and our DNA repair. After a few billion years of advancement since the days of yeast, they have evolved to control our health, our fitness, and our very survival. They have also evolved to require a molecule called nicotinamide adenine dinucleotide, or NAD. As we will see later, the loss of NAD as we age, and the resulting decline in sirtuin activity, is thought to be a primary reason our bodies develop diseases when we are old but not when we are young.

1800, the global literacy rate was 12 percent, by 1900 it was 21 percent, and today it's 85 percent.

How does the SIR2 gene actually turn off genes? SIR2 codes for a specialized protein called a histone deacetylase, or HDAC, that enzymatically cleaves the acetyl chemical tags from histones, which, as you'll recall, causes the DNA to bundle up, preventing it from being transcribed into RNA.