Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: LOCALIZATION OF REPETITIVE AND SINGLE COPY SEQUENCE ON MEIOTIC
PACHYTENE AND MITOTIC METAPHASE CHROMOSOMES OF TOMATO USING
FLUORESCENCE IN SITU HYBREDIZATION (FISH)
LOCALIZATION OF REPETITIVE AND SINGLE COPY SEQUENCE ON MEIOTIC
PACHYTENE AND MITOTIC METAPHASE CHROMOSOMES OF TOMATO USING
FLUORESCENCE IN SITU HYBREDIZATION (FISH)
Xiaobo Zhong 1, Hans de Jong 2, and Pim Zabel 1, Wageningen
Agricultural University, Departments of Molecular Biology 1,
and Genetics 2, Wageningen, The Netherlands
Recently, an integrated molecular/classical linkage map of
tomato chromosome has been established, showing the positions of
over 40 DNA markers relative to 10 classical markers (Weide et
al, 1993 Genetics in press). With the final goal of developing a
cytogenetically based physical map of chromosomal 6 that shows
the order of loci from the genetic linkage map with respect to
cytological landmarks, we have started a molecular cytogenetic
study using fluorescence in situ hybridization (FISH). Tomato
chromosomes at mitotic metaphase are not particular
suitable for high resolution physical mapping by their short
length. In contrast, chromosomes at meiotic pachytene stage are
about 10 times longer, and easier to identify by their
differences in chromosome arm lengths and chromomere pattern. We
have developed a technique for preparing chromosomal spreads of
young pollen mother cells at mid-prophase I which allows multiple
sequences to be detected simultaneously using differently
coloured probes. In a first series of experiments, the
hybridization patterns of four classes of repetitive DNA
sequences (ribosomal DNA; TGRI, telomere specific repeat; THG2,
dispersed repeat; and GATA repeat, heterochromatin specific) were
studied in single and multicoloured FISH. In addition to the
repetitive DNA sequences, a start was made to map chromosome 6
specific yeast artificial chromosome (YAC) clones. Preliminary
data suggest that FISH of tomato chromosomes at pachytene stage
provides a powerful means to develop a cytogenetically based
physical map.
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