The Estimated Number of Genes in the Human Genome
Despite the ubiquity of high-throughput sequencing technologies, the estimated number of genes in the human genome is still uncertain. The current consensus estimates that there are 20,500 genes. This number is relatively low compared to the number of genes in other multi-cellular organisms. The number of protein-coding genes is also relatively low. However, researchers have discovered hundreds of new coding exons.
The human genome is composed of a mixture of coding and noncoding DNA. The coding DNA is the sequences that are translated into proteins. Typically, this DNA comprises 2% of the genome. The remainder is composed of noncoding DNA, which includes untranslated components of protein-coding genes. Noncoding DNA is mainly composed of simple repetitive sequences, transposons, and pseudogenes.
In addition to coding and noncoding DNA, the human genome contains many transposons. Transposons are repetitive DNA sequences that insert themselves into host genomes. Transposons have played an important role in sculpting the human genome. The number of transposons in the human genome is very high. They have been found in approximately half of all humans.
The haploid genome of humans contains 3,054,815,472 base pairs. Haploid genomes are found in germ cells. In some species, such as humans, a haploid genome has a smaller number of genes than the euchromatic genome.
The number of proteins in the human genome is also variable. Researchers have discovered that almost one third of the human genome translates the same protein as the orthologs of chimpanzees.