Genomstørrelse

Genomstørrelse, or genome size, is the total amount of DNA contained in a haploid genome. It is typically expressed in base pairs (bp) or in mass as picograms (pg), with 1 pg approximately equal to 978 megabase pairs (Mbp). Genome size is a basic genomic characteristic used in comparative studies and sequencing projects.

Genome sizes vary dramatically across life forms. For example, human haploid genomes are about 3.2 Gb (gigabase pairs), while some plants and amphibians have genomes that are much larger, and certain insects or fungi have smaller ones. Genome size does not correlate cleanly with organismal complexity, a phenomenon known as the C-value paradox. Much of the variation arises from differences in repetitive DNA, transposable elements, and whole-genome duplications rather than coding gene content.

Measurement methods include flow cytometry, which estimates DNA content from cell nuclei, and Feulgen densitometry. Advances in sequencing and bioinformatics also allow estimation from sequencing read data and k-mer analysis. These methods are complemented by cytological techniques that count chromosomes in some species.

Factors influencing genome size include polyploidy, transposable element activity, and the pace of DNA loss or deletion. Evolutionary and ecological factors can shape genome size over time, leading to clade-specific trends (for example, some birds have relatively compact genomes, while some plants and amphibians retain large, repeat-rich genomes).

Understanding genomstørrelse informs studies of genome evolution, assembly strategies for sequencing projects, and interpretations of ecological and developmental biology across taxa.