DNA

The human body is made up of  fifty trillion cells. Cells come in many different varieties. Nucleus contains 99.9%  of the genes. 20,000 Genes are small parts of a molecule called DNA and are coiled. DNA is a double stranded molecule containing four bases and sugar and phosphate. The bases spell the genetic code and determine the physical structure. Most genes are passed down from generation to generation. Genes tell a cell how to function and what traits to express. Gene regulators turn things on and off to control cell function. These bases, adenine (abbreviated A), cytosine (C), guanine (G) and thymine (T) are organised into pairs that make up the chromosomes. Humans have 23 pairs of chromosomes. 98.5% similar to chimpanzees. An entire set is called genome. SNPS (single nucleotide polymorphism) account for differences and others, how we develop diseases or respond to drugs. The  parents both equally make up the 23 pairs of chromosomes, the genes make up the individual’s appearance and physical structure together form a homologous chromosome. Changes can occur environmentally, chemically and biologically and result in variation. Although genotypes are almost identical amongst species, the environment and inheritance causes this to occur.