GENES, MUTATIONS, AND CANCER

These connections with environmental factors suggest that some cancers could originate from agents that change a cell’s genetic material (mutation). Each of the more than 100 trillion cells in a human body carries its genetic information in deoxyribonucleic acid (DNA), composed of long double-helical strands made of sequences of four building blocks (bases) linked in pairs. It is packaged in 23 pairs of chromosomes which can be seen with a microscope. The DNA in each cell carries information equal to the letters in 600 encyclopedia volumes. Genes are sequences of DNA that code for individual proteins.

Mutations are errors in DNA structure that alter this genetic information. Most mutations arise spontaneously, possibly from mistakes that arise while DNA duplicates during cell growth. Experiments have shown that foods contain many chemicals that cause carcinogenic damage to DNA. Errors can also be produced by damage from toxic chemicals (carcinogens) or radiation. Cell growth is stopped when molecular mechanisms termed checkpoints sense the damage, recruit the molecules to rectify the problem, and give time for corrections to be made.

Then enzymes for repair are activated, and the cell may recover if the damage was not too severe. Genes designated BRCA1 and BRCA2 are involved in DNA repair and are mutated in some breast and ovarian cancers. The inability to repair damaged DNA may result in cancer.