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81.
An exception to the generally conservative nature of plastid gene evolution
is the gene coding for the beta" subunit of RNA polymerase, rpoC2. Previous
work by others has shown that maize and rice have an insertion in the
coding region of rpoC2, relative to spinach and tobacco. To assess the
distribution of this extra coding sequence, we surveyed a broad
phylogenetic sample comprising 55 species from 17 angiosperm families by
using Southern hybridization. The extra coding sequence is restricted to
the grasses (Poaceae). DNA sequence analysis of 11 species from all five
subfamilies within the grass family demonstrates that the extra sequence in
the coding region of rpoC2 is a repetitive array that exhibits more than a
twofold increase in nucleotide substitution, as well as a large number of
insertion/deletion events, relative to the adjacent flanking sequences. The
structure of the array suggests that slipped-strand mispairing causes the
repeated motifs and adds to the mechanisms through which the coding
sequence of plastid genes are known to evolve. Phylogenetic analyses based
on the sequence data from grass species support several relationships
previously suggested by morphological work, but they are ambiguous about
broad relationships within the family.
相似文献
82.
Bo Chang Richard S Smith Maureen Peters Olga V Savinova Norman L Hawes Adriana Zabaleta Steven Nusinowitz Janice E Martin Muriel L Davisson Constance L Cepko Brigid LM Hogan Simon WM John 《BMC genetics》2001,2(1):1-12
Background
Glaucoma is a common disease but its molecular etiology is poorly understood. It involves retinal ganglion cell death and optic nerve damage that is often associated with elevated intraocular pressure. Identifying genes that modify glaucoma associated phenotypes is likely to provide insights to mechanisms of glaucoma. We previously reported glaucoma in DBA/2J mice caused by recessive alleles at two loci, isa and ipd, that cause iris stromal atrophy and iris pigment dispersion, respectively. A approach for identifying modifier genes is to study the effects of specific mutations in different mouse strains. When the phenotypic effect of a mutation is modified upon its introduction into a new strain, crosses between the parental strains can be used to identify modifier genes. The purpose of this study was to determine if the effects of the DBA/2J derived isa and ipd loci are modified in strain AKXD-28/Ty. 相似文献83.
S S Howards C J Flickinger D W Noller W B Panko 《Journal of reproduction and fertility》1979,55(2):401-405
The effects of vasectomy on testicular DNA production were studied in guinea-pigs at 2 weeks and 2 and 6 months after surgery. By 6 months, vasectomy had resulted in lower testicular weight and absolute DNA, RNA and protein contents, although RNA and DNA concentrations/protein were unchanged. Incorporation of thymidine into the testis had decreased by 2 weeks after vasectomy, and continued to do so unless the ductal system subsequently ruptured and formed a granuloma when thymidine incorporation returned to normal control levels. It is suggested that in the guinea=pig vasectomy alters spermatogenesis by reducing testicular DNA synthesis. 相似文献