Why does the Genome Size Differ in Different Organisms?
Genome size differs in different organisms for reasons not entirely known to modern science. Genome size is loosely correlated with complexity in many cases, but there are numerous notable exceptions. For example, certain bacteria and many plant species have larger genomes than humans. A term frequently used interchangeably with genome size is “C-value.” This is an abbreviation for the word “constant,” a reference to the fact that genome size between individuals of the same species is roughly constant. The question of why certain simple organisms have large genomes is called the “C-value enigma” in biology. The discovery of “junk DNA,” or non-coding DNA, in the early 1970s partially solved the C-value enigma. Junk DNA does not code for proteins, and although there is recent evidence that it may regulate how genes turn on and off, it does not contribute nearly as much biological complexity as the portion of the DNA that contains actual genes. If you account for junk DNA, the number of g
