Highly conserved linkage homology between birds and turtles: bird and turtle chromosomes are precise counterparts of each other.
The karyotypes of birds, turtles and snakes are characterized by two distinct chromosomal components, macrochromosomes and microchromosomes. This close karyological relationship between birds and reptiles has long been a topic of speculation among cytogeneticists and evolutionary biologists; however, there is scarcely any evidence for orthology at the molecular level. To define the conserved chromosome synteny among humans, chickens and reptiles and the process of genome evolution in the amniotes, we constructed comparative cytogenetic maps of the Chinese soft-shelled turtle (Pelodiscus sinensis) and the Japanese four-striped rat snake (Elaphe quadrivirgata) using cDNA clones of reptile functional genes. Homology between the turtle and chicken chromosomes is highly conserved, with the six largest chromosomes being almost equivalent to each other. On the other hand, homology to chicken chromosomes is lower in the snake than in the turtle. Turtle chromosome 6q and snake chromosome 2p represent conserved synteny with the chicken Z chromosome. These results suggest that the avian and turtle genomes have been well conserved during the evolution of the Arcosauria. The avian and snake sex Z chromosomes were derived from different autosomes in a common ancestor, indicating that the causative genes of sex determination may be different between birds and snakes.
Matsuda
Yoichi
Y
Laboratory of Animal Cytogenetics, Division of Genome Dynamics, Creative Research Initiative "Sousei", Hokkaido University, North 10 West 8, Kita-ku, Sapporo 060-0810, Japan. yoimatsu@ees.hokudai.ac.jp
Nishida-Umehara
Chizuko
C
Tarui
Hiroshi
H
Kuroiwa
Asato
A
Yamada
Kazuhiko
K
Isobe
Taku
T
Ando
Junko
J
Fujiwara
Atushi
A
Hirao
Yukako
Y
Nishimura
Osamu
O
Ishijima
Junko
J
Hayashi
Akiko
A
Saito
Toshiyuki
T
Murakami
Takahiro
T
Murakami
Yasunori
Y
Kuratani
Shigeru
S
Agata
Kiyokazu
K
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001717:Birds / Q000235:genetics*; D002875:Chromosomes; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D008040:Genetic Linkage; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics; D014426:Turtles / Q000235:genetics*
C110547:DMRT1 protein; D017931:DNA Primers; D018076:DNA, Complementary; D014157:Transcription Factors