It is shown that in the genomes of warm-blooded vertebrates the elevation of genic GC-content is associated with an increase in the bendability of the DNA helix, which is both absolute and relative as compared with random sequences. This trend takes place both in exons and introns, being more pronounced in the latter. At the same time, the free energy of melting (delta G) of exons and introns increases only absolutely with elevation of GC-content, whereas it decreases as compared with random sequences (again, this trend is stronger in the introns). In genes of cold-blooded animals, plants, and unicellular organisms, these regularities are weaker and often not consistent. Generally, there is a negative correlation between bendability and melting energy at any fixed GC-content value. This effect is stronger in the introns. These findings suggest that GC-enrichment of genes in the homeotherm vertebrates can be caused by selection for increased bendability of DNA.