All the genes present in a set of chromosomes are collectively called the genome. German botanist Hans Winkler first used the term genome in 1920. The human genome contains about 3000 million base pairs and 20,000-25,000 genes. In 2007, 2900 million nucleotides and about 30,000 genes were recorded in the human genome. 99.9 percent of human genomes (genes) are identical. Due to the difference in the structure of only 0.1% of the genes, there are different types of people in the world. Only 2% of human genes express the trait. The remaining 98% of genes are inactive. These inactive genes (98%) are called junk DNA. Mycoplasma genitalium has 517 genes, E. coli has 5416 genes and Arabidopsis thaliana has 25,000 genes.