Hello and welcome to this introduction of the SkewDB. This open (downloadable) database contains details of GC skew, plus a dozen other skews, for all 28,000 bacterial chromosomes available through the NCBI genomes service. The database is created using the open source Antonie DNA software. There is also an online viewer that includes graphs. GC skew is the phenomenon where almost all circular chromosomes tend to have near equal amounts of G and C nucleotides, per strand, but where the leading replication strand contains an excess of G, and the lagging replication strand has an excess of C nucleotides.