GC-content

In molecular biology and genetics, GC-content (or guanine-cytosine content) is the percentage of nitrogenous bases in a DNA or RNA molecule that are either guanine (G) or cytosine (C).

[17] Comparison of more than 1,000 orthologous genes in mammals showed marked within-genome variations of the third-codon position GC content, with a range from less than 30% to more than 80%.

However, a species with an extremely low GC-content is Plasmodium falciparum (GC% = ~20%),[23] and it is usually common to refer to such examples as being AT-rich instead of GC-poor.

These GC-content changes are correlated with species life-history traits (e.g., body mass or longevity) and genome size,[18] and might be linked to a molecular phenomenon called the GC-biased gene conversion.

[25] In polymerase chain reaction (PCR) experiments, the GC-content of short oligonucleotides known as primers is often used to predict their annealing temperature to the template DNA.

Bird genomes are known to have many such parts, causing the problem of "missing genes" expected to be present from evolution and phenotype but never sequenced — until improved methods were used.

[26] The species problem in non-eukaryotic taxonomy has led to various suggestions in classifying bacteria, and the ad hoc committee on reconciliation of approaches to bacterial systematics of 1987 has recommended use of GC-ratios in higher-level hierarchical classification.

[29] With the use of more reliable, modern methods of molecular systematics, the GC-content definition of Actinomycetota has been abolished and low-GC bacteria of this clade have been found.