Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: LOCALIZATION OF RIBOSOMAL RNA GENES ON RICE CHROMOSOMES
LOCALIZATION OF RIBOSOMAL RNA GENES ON RICE CHROMOSOMES.
Mei-Chu Chung, Chii-Nien Ning and Hsin-Kan Wu, Institute of
Botany, Academia Sinica, Taipei, Taiwan, 11529, ROC.
Although it has been known that the number of nucleolus in
rice somatic cells at telophase varies from two to four, the
number of nucleolar chromosomes was figured out only recently.
This paper located the rRNA genes coding for 18S-5.8S-25S rRNA
at the short arm end of chromosome pairs 8 and 10 and that for
5S rRNA at the short arm region, very close to the centromere of
chromosomes 7, 9 and 11 by in situ hybridizing chromosome
complement to the rDNA probes. The number of the repeating
unit resided on chromosome 8 was found to exceed that on
chromosome 10. It also suggested that the number of nucleolus
at pachytene as well as at prometaphase does not necessarily
correspond to the number of nucleolar chromosome that is species
(or subspecies) specific due to the fusion of the rRNA molecules
transcribed by genetically homozygous rDNA alleles in one or two
different loci. The transcription of rRNA at the rDNA
corresponding to the thread like DNA segment extending from the
short arm end of chromosome 8 may be still in process at
prometaphase.
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