Functional organization of the Human Genome

    The human genome comprises an estimated 20,500 "genes", which can be assigned to functional categories as above. Only about 20% of the transcripts are responsible for classical biochemical functions, loosely catalytic enzymes. Approximately a quarter of the genome is responsbile for maintenance of the genome itself, including polymerases, ligases, helicases, etc. as discussed under DNA replication, transcription and control of transcription, and translation Another 21% are responsible for signal transduction, for example relaying information about the extracellular environment across the cell membrane to the cell nucleus, so as to produce the appropriate response by change in gene expression.The function of more than a third of the genome is at present unknown. Inference of the function of this portion of the genome proceeds by identification of sequence motifs and comparison with homologous genes in other creatures.

Figure ©2012 TA Brown, Introduction to Genetics (1st ed.); additional text ©2014 by Steven M. Carr