For all but four diseases, the genetic data would fail to determine who is likely to contract the condition in most cases,

genetics are only part of the story when it comes to determining health. Lifestyle, environment and random chance play a bigger role than genes, or work with genes, to cause or protect against disease.

Drugs that alter some chemical tags on DNA make cancer cells behave more like normal cells

And the drugs seem to make cancer cells more susceptible to chemotherapy and attacks from the immune system.

drugs called azacitidine and decitabine, when used in low doses, change gene activity in leukemia and breast cancer cells in the lab. If DNA is a cell’s hard drive, then chemical tags attached to the DNA or DNA-packaging proteins called histones serve as software packages to tell the hard drive how to function. This type of chemical programming is called epigenetics.

The human genome contains 3164.7 million chemical nucleotide bases (A, C, T, and G).

The average gene consists of 3000 bases, but sizes vary greatly, with the largest known human gene being dystrophin at 2.4 million bases.

Genes are especially important segments of DNA that directly influence one or more traits. They are relatively small segments of chromosomes, where the sequence of DNA nucleotides encodes a recipe for making a protein. Small differences in the sequence of DNA nucleotides of a particular gene can lead to differences in the structure and behavior of the proteins they encode. It is these differences, in turn, that account for the variable characteristics of the people around you.