Gene mapping studies confirm the homology between the platypus X and echidna X1 chromosomes and identify a conserved ancestral monotreme X chromosome

  title={Gene mapping studies confirm the homology between the platypus X and echidna X1 chromosomes and identify a conserved ancestral monotreme X chromosome},
  author={Jaclyn M. Watson and Arthur D. Riggs and Jennifer A Marshall Graves},
The identification of the sex chromosomes in the three extant species of Prototherian mammals (the monotremes) is complicated by their involvement in a multivalent translocation chain at the first division of male meiosis. The platypus X chromosome, identified by the presence of two copies in females and one in males, has been found to possess a suite of genes that have been mapped to the X chromosomes of all eutherian and metatherian mammals. We have extended gene mapping studies to a member… 

The monotreme genome: a patchwork of reptile, mammal and unique features?

Evolution of mammal sex and sex chromosomes : the contribution of monotreme cytogenetics

Therian mammals (placentals and marsupials) all share an XX female: XY male sex chromosome system, and mutation analysis and transgenic experiments in placental mammals show that male development is initiated by the SRY gene located on the Y chromosome, and female development ensues in the absence of SRY.

Development of microsatellite markers for the short-beaked echidna using three different approaches

The genomic sequencing approach using data derived from the Roche FLX platform is likely to provide the most promising method to develop echidna microsatellites, which will be useful tools to study population genetic structure, gene flow, kinship and parentage in Tachyglossus sp.

BAC Libraries: Precious Resources for Marsupial and Monotreme Comparative Genomics

This chapter will review the important role BACs have played in marsupial and monotreme comparative genomics studies, and the inclusion of these interesting species in such studies has provided great insight and often surprising findings regarding gene and genome evolution.

Intersex/Gender-Related Constitutiveness: Specific Realities, Specific Norms

Following traditional scientific standards and categories on the basis of classical dichotomies, disorder is assigned to large minorities, thus making the physical image treatable, thus keeping existing scientific and cultural suppositions reproducible.



The X chromosome of monotremes shares a highly conserved region with the eutherian and marsupial X chromosomes despite the absence of X chromosome inactivation.

It is concluded that the long arm of the human X chromosome represents a highly conserved region that formed part of the X chromosome in a mammalian ancestor at least 150 million years ago.

Sex chromosome evolution: platypus gene mapping suggests that part of the human X chromosome was originally autosomal.

It is reported that several genes located on the short arm of the human X chromosome are absent from the platypus X chromosomes, as well as from the marsupial X chromosome, implying that the whole human X short arm region is a relatively recent addition to the X chromosome in eutherian mammals.

Monotreme Genetics and Cytology and a Model for Sex-Chromosome Evolution

The results suggest that sex chromosome differentiation in the monotremes represents an intermediate stage in the evolution of the dimorphic sex chromosomes of therian mammals and that X-chromosome inactivation may also represent a comparatively primitive stage.

Conserved regions of homologous G-banded chromosomes between orders in mammalian evolution: carnivores and primates.

  • W. NashS. O’Brien
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 1982
A comparison of homologous (by linkage criteria) chromosomes by using conventionally extended and high-resolution G-banding of human and feline chromosomes is presented and five subchromosomal regions (homologous to human chromosome 1p, 2p,2q, 12, and X) were found to be conserved and homologously by all the stated criteria.

The androgen receptor gene is located on a highly conserved region of the X chromosomes of marsupial and monotreme as well as eutherian mammals.

It is concluded that the androgen receptor gene is part of a highly conserved region of the mammalian X, represented by the human Xq, which formed part of the X chromosome in a mammalian ancestor 150 million years ago.

Karyotypic conservation in the mammalian order monotremata (subclass Prototheria)

The order Monotremata, comprising the platypus and two species of echidna (Australian and Nuigini) is the only extant representative of the mammalian subclass Prototheria, which diverged from

Chromosomal evolution in Primates: Tentative phylogeny from Microcebus murinus (Prosimian) to man

The karyotypes of more than 60 species of Primates are studied and compared, with the use of almost all existing banding techniques, and a fairly precise genealogy of many Primates is proposed, giving the positions of the Catarrhines, the Platyrrhines, and the Prosimians is proposed.

Autosomal assignment of OTC in marsupials and monotremes: implications for the evolution of sex chromosomes.

It is proposed that an autosomal or pseudoautosomal segment containing OTC has been recruited into the inactivated region of the X rather recently in eutherian evolution while it remained autosomal, or was translocated to an autosome, in metatherian and prototherian mammals.

Mammalian sex chromosomes: Evolution of organization and function

Comparisons of the sex chromosomes in these three major groups of extant mammals are reviewed, and it is shown how they have led to a new view of the evolution of mammalian sex chromosome organization and function in sex determination and X chromosome inactivation.

A unique cytogenetic system in monotremes

All 3 extant genera of monotremes show a unique kind of cytogenetic system involving the formation of a structurally heterozygous chain multiple apparently coupled with a system of complementary