Editing Genome (section)

== Genome evolution ==
Genomes are more than the sum of an organism's [[gene]]s and have traits that may be [[Measurement|measured]] and studied without reference to the details of any particular genes and their products. Researchers compare traits such as [[karyotype]] (chromosome number), [[genome size]], gene order, [[codon usage bias]], and [[GC-content]] to determine what mechanisms could have produced the great variety of genomes that exist today (for recent overviews, see Brown 2002; Saccone and Pesole 2003; Benfey and Protopapas 2004; Gibson and Muse 2004; Reese 2004; Gregory 2005).

[[gene duplication|Duplications]] play a major role in shaping the genome. Duplication may range from extension of [[short tandem repeats]], to duplication of a cluster of genes, and all the way to duplication of entire chromosomes or even [[polyploidy|entire genomes]]. Such duplications are probably fundamental to the creation of genetic novelty.

[[Horizontal gene transfer]] is invoked to explain how there is often an extreme similarity between small portions of the genomes of two organisms that are otherwise very distantly related. Horizontal gene transfer seems to be common among many [[microbe]]s. Also, [[Eukaryote|eukaryotic cells]] seem to have experienced a transfer of some genetic material from their [[chloroplast]] and [[mitochondria]]l genomes to their nuclear chromosomes. Recent empirical data suggest an important role of viruses and sub-viral RNA-networks to represent a main driving role to generate genetic novelty and natural genome editing.