Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Comparative Study
, 8 (6), 418-22

Comparative Chromosome Painting Between Two Marsupials: Origins of an XX/XY1Y2 Sex Chromosome System

Comparative Study

Comparative Chromosome Painting Between Two Marsupials: Origins of an XX/XY1Y2 Sex Chromosome System

R Toder et al. Mamm Genome.


Cross-species chromosome painting was used to investigate genome rearrangements between tammar wallaby Macropus eugenii (2n = 16) and the swamp wallaby Wallabia bicolor (2n = 10female symbol/11male symbol), which diverged about 6 million years ago. The swamp wallaby has an XX female:XY1Y2 male sex chromosome system thought to have resulted from a fusion between an autosome and the small original X, not involving the Y. Thus, the small Y1 should represent the original Y and the large Y2 the original autosome. DNA paints were prepared from flow-sorted and microdissected chromosomes from the tammar wallaby. Painting swamp wallaby spreads with each tammar chromosome-specific probe gave extremely strong and clear signals in single-, two-, and three-color FISH. These showed that two tammar wallaby autosomes are represented unchanged in the swamp wallaby, two are represented by different centric fusions, and one by a tandem fusion to make the very long arms of swamp wallaby Chromosome (Chr) 1. The large swamp wallaby X comprises the tammar X as its short arm, and a tandemly fused 7 and 2 as the long arm. The acrocentric swamp wallaby Y2 is a 2/7 fusion, homologous with the long arm of the X. The small swamp wallaby Y1 is confirmed as the original Y by its painting with the tammar Y. However, the presence of sequences shared between the microdissected tammar Xp and Y on the swamp wallaby Y2 implies that the formation of the compound sex chromosomes involved addition of autosome(s) to both the original X and Y. We propose that this involved fusion with an ancient pseudoautosomal region followed by fission proximal to this shared region.

Similar articles

See all similar articles

Cited by 26 PubMed Central articles

See all "Cited by" articles


    1. Proc Natl Acad Sci U S A. 1982 Nov;79(21):6631-5 - PubMed
    1. Chromosoma. 1997 Jul;106(2):94-8 - PubMed
    1. Hum Genet. 1988 Nov;80(3):224-34 - PubMed
    1. Chromosome Res. 1996 Jun;4(4):295-300 - PubMed
    1. Chromosome Res. 1996 Apr;4(3):218-25 - PubMed

Publication types

LinkOut - more resources