Genes are part of the DNA sequence called coding DNA. Noncoding DNA represents sequences that do not have genes and only recently have found to have many new important functions. Out of the 3 billion base pairs that exist in the human DNA, there are only about 40,000 genes. The noncoding sections of DNA within a gene are called introns, while the coding sections of DNA are called exons. After transcription of DNA to RNA, the RNA is processed. Introns from the mRNA are excised out of the newly formed mRNA molecule before it leaves the nucleus.