DNA contains genes that code for proteins and RNA. Genes are segments of DNA found on chromosomes in the cell nucleus. Chromosomes are made of DNA coiled around histone proteins. Humans have 46 chromosomes that come in 23 pairs, with one set from each parent. Chromosomes contain genes and determine traits through their DNA sequence. Changes to genes through mutations can lead to uncontrolled cell growth and cancer if they alter proteins that regulate the cell cycle.