1022-7954/02/3811- $27.00 © 2002
Russian Journal of Genetics, Vol. 38, No. 11, 2002, pp. 1251–1255. From Genetika, Vol. 38, No. 11, 2002, pp. 1480–1484.
Original English Text Copyright © 2002 by Meisheng, Qixing.
The origin and evolution of sex chromosomes of
vertebrates is an important issue in evolutionary genet-
ics. In mammals, the male is the heterogametic sex (XY
male and XX female). The Y chromosome-linked gene
SRY determines the phenotype of male development .
The human sex chromosomes are thought to have
evolved from a ordinary pair of autosomes that existed
in the genome of the vertebrate ancestor [2–4], but all
the evidence for it comes from the studies on sex chro-
mosomes of mammals. In fact, despite extensive stud-
ies [5–10], it is still unclear how the complex sex deter-
mination systems evolve and sex chromosome origi-
nate. Fish show a large degree of plasticity in sex
determination and in appearance of sex chromosomes.
Different ﬁsh have different sex determination systems,
ranging from undifferentiated sex chromosomes, XY-XX,
ZZ-ZW, XO-XX, multi-sex chromosomes to nature
hermaphroditism . To gain clues about the origin of
human sex chromosomes, we used the entire human X
and Y chromosome-speciﬁc DNA as probes to paint
chromosomes of three ﬁsh species,
= 50) and
= 48), which represent
three different orders: Synbrachiformes, Gyprini-
formes, and Perciformes, respectively.
Recently, it was shown that comparative chromo-
some painting provided a powerful and rapid technique
to investigate the conserved segments and to analyze
the evolutionary relations among distantly related spe-
cies [12–16]. Although it provides no information
about the gene order within the conserved segments
identiﬁed, it can give the forceful cytogenetics evidence
for the rules of the chromosomal evolution . Here
we applied a comparative chromosome painting strategy
between more distantly related vertebrate species, human
and ﬁsh, to detect the conserved sex chromosomal seg-
ments which might be useful to explain how the sex chro-
mosomes of vertebrates originated and evolved.
MATERIALS AND METHODS
was provided by the Institute of Hydro-
biology, Chinese Academy of Sciences,
) was purchased from a market in Wuhan
was collected from the Long Lake in Jingsha City (China).
The human X and Y chromosome-speciﬁc DNA plasmid
libraries were the gift by Anna Jauch (University of
Heidelberg, Germany) and were described in detail by
The embryos of
at the early developmental stage were used to prepare
the metaphase spreads. The spreads of
for in situ hybridization experiments were
prepared as reported .
The plasmid libraries were ampli-
ﬁed and the plasmids were extracted as Sambrook
detailed . The inserts in the libraries were obtained
by PCR with T3 and T7 primers: 94
C 30 s, 57
C 45 s,
C 1 min for 35 cycles. The PCR products were puri-
ﬁed by SPIN-200 (Clontech) and labeled with biotin-
11-dUTP by random primers.
Chromosome painting to
ﬁsh metaphase chromosomes and detection of hybrid
molecules were performed as described . Brieﬂy,
l of the hybridization mixture [50%(vol/vol) for-
SSC/10%(W/vol) dextran sulfatate (pH7.0)]
containing 200 ng of labeled plasmid library inserts,
Sex Chromosomal Homologies between Human
and Fish Karyotypes Revealed by Chromosome Painting*
Yi Meisheng and Yu Qixing
Department of Genetics, College of Life Sciences, Wuhan University, Wuhan 430072, China;
fax: 0086-027-87882661; e-mail: firstname.lastname@example.org
Received December 19, 2000
—Human sex chromosome-speciﬁc probes were hybridized to metaphase spreads of three ﬁsh spe-
Basilewsky, to reveal evolutionary
conservation of sex chromosomal segments between distantly related species of vertebrates. The human X chro-
mosomal paint disclosed 4, 8, and 6 conserved syntenic segments in the karyotypes of the three ﬁsh species
respectively, which were scattered in several pairs of homologous chromosomes. But no conserved segment
was identiﬁed in our experiments when the human Y chromosomal probes were used. The evolution of the
X chromosome of vertebrates is discussed.
* This paper was presented by the authors in English.