Heterogeneous gene distribution reflects human genome complexity as detected at the cytogenetic level

Human chromosomes are heterogeneous in structure and function and this is
the base for the specific banding patterns produced by various chromosome
staining techniques. The Human Genome Data Base as if January 2001 was
searched for genes mapped to individual chromosomal bands to study the
different aspects of human genome organization as they appear at the
cytogenetic level of resolution. Genes are unequally distributed both on
human chromosomes and chromosome bands. Among more than 5000 genes mapped
at individual bands, 81% were located in G-negative bands, which
correspond to half of the human genome. The main practical value of having
a dense genetic physical map of genes is to accelerate the discovery by
positional candidate cloning of human disease. Gene content agrees with H3
family isochores and with GC-rich flavors. Interestingly, two G-positive
bands, namely 2p chromosome bandings is 12 and 7q35, containing a high
number of genes. The finding of heterogeneity in gene content suggests
that chromosome banding is not only due to differences in gene content.