In summary, the exon/intron structure of the chicken type II collagen gene is identical with that of the chicken alpha 2(I) collagen gene and differs at only one known position from the human and mouse alpha 1(I) genes. However, the chicken type II gene is different from the chicken alpha 2(I) gene in that it is considerably shorter because of a much smaller average intron size and in that the G+C composition of the introns is much higher. The codon usage of the type II genes also shows characteristic differences. There is a single copy of the chick type II gene per haploid genome.