GC skew

GC skew is when the nucleotides Guanine and Cytosine are over- or under-abundant in a particular region of DNA or RNA. In equilibrium conditions (without mutational or selective pressure and with nucleotides randomly distributed within the genome) there is an equal frequency of the four DNA bases (Adenine, Guanine, Thymine, and Cytosine) on both single strands of a DNA molecule. However, in most bacteria (e.g. E. coli) and some archaea (e.g. Sulfolobus solfataricus), nucleotide compositions are asymmetric between the leading strand and the lagging strand: the leading strand contains more Guanine (G) and Thymine (T), whereas the lagging strand contains more Adenine (A) and Cytosine (C). This phenomenon is referred to as GC and AT skew. It is represented mathematically as follows: GC skew is when the nucleotides Guanine and Cytosine are over- or under-abundant in a particular region of DNA or RNA. In equilibrium conditions (without mutational or selective pressure and with nucleotides randomly distributed within the genome) there is an equal frequency of the four DNA bases (Adenine, Guanine, Thymine, and Cytosine) on both single strands of a DNA molecule. However, in most bacteria (e.g. E. coli) and some archaea (e.g. Sulfolobus solfataricus), nucleotide compositions are asymmetric between the leading strand and the lagging strand: the leading strand contains more Guanine (G) and Thymine (T), whereas the lagging strand contains more Adenine (A) and Cytosine (C). This phenomenon is referred to as GC and AT skew. It is represented mathematically as follows: