C-value paradox

The C-value paradox describes the observation that the chromatin content of eukaryotic genomes does not correlate with the complexity of the respective organism and not with the number of genes an organism possesses. In genetics, the C value is a measure of the total amount of DNA in a haploid genome .

The highest chromatin content (the largest genomes) is not found in animals, for example, among birds or mammals, but in amphibians , which are considered to be less complex. The largest genomes ever found have plants, namely lily-like .

The main reason for this is the high proportion of non-coding DNA in eukaryotic genomes. Repetitive sequences and satellite DNA make up the largest share . But introns and inactivated retroviruses also contribute to this. In prokaryotes introns and non-coding DNA sequences are extremely rare. The number of genes can therefore be roughly estimated from the size of the genome: The average size of a bacterial gene is 1 kb . The genome size divided by 1000 is roughly the number of genes in a bacterium or archaeon .

literature

• James E. Darnell , Harvey Lodish, David Baltimore : Molecular Cell Biology . de Gruyter, Berlin et al. 1993, ISBN 3-11-011934-X (4th edition. Harvey Lodish: Molecular Cell Biology. Spectrum Akademischer Verlag, Heidelberg et al. 2001, ISBN 3-8274-1077-0 ).
• Benjamin Lewin: Molecular Biology of Genes . Spektrum Akademischer Verlag, Heidelberg et al. 1998, ISBN 3-8274-0234-4 .
• William S. Klug, Michael R. Cummings, Charlotte A. Spencer: Genetics . 8th, updated edition 2007, ISBN 978-3-8273-7247-5 .