Volume 85, Issue 2
August 2006, pages 93-160
pp 93-97 August 2006 Perspectives
Bohr, Delbrück and Schrödinger were physicists who had important influences on biology in the second half of the twentieth century. They thought that future studies of the gene might reveal new principles or paradoxes, analogous to the wave/particle paradox of light propagation, or even new physical laws. This stimulated several physicists to enter the field of biology. Delbrück founded the bacteriophage group which provided one of the roots of molecular biology. Another was X-ray crystallography which led to the discovery of DNA structure. The strength and success of molecular biology came from the many interactions between geneticists, physicists, chemists and biochemists. It was also characterized by a powerful combination of theoretical and experimental approaches.
pp 99-99 August 2006 Commentary on J. Genet. Classic
pp 101-105 August 2006
The phenotype of the ‘assimilated bithorax’ stock is due in part to a number of genes, on all the chromosomes, which act directly on the individuals containing them, and partly to a recessive X-chromosome condition which causes a maternal effect.
Attempts to break down the maternal-effect condition by crossing-over were unsuccessful.
The maternal effect condition, when made homozygous in a wild-type background, causes the appearance of some bithoraxes in the next generation.
The condition may have arisen by mutation during the course of the selection by which the assimilated stock was built up, but it may have been present in very low frequency in the initial population.
The offspring of females homozygous for the maternal-effect condition do not produce a higher percentage of bithoraxes, following ether treatment, than do flies of similar genotype from other mothers.
pp 107-116 August 2006 Research Article
Using oligonucleotide primers designed to match hypervariable segments I (HVS-1) ofPanthera tigris mitochondrial DNA (mtDNA), we amplified two different PCR products (500 bp and 287 bp) in the tiger (Panthera tigris), but got only one PCR product (287 bp) in the leopard (Panthera pardus). Sequence analyses indicated that the sequence of 287 bp was a D-loop-like nuclear mitochondrial sequence (Numts), indicating a nuclear transfer that occurred approximately 4.8–17 million years ago in the tiger and 4.6–16 million years ago in the leopard. Although the mtDNA D-loop sequence has a rapid rate of evolution, the 287-bp Numts are highly conserved; they are nearly identical in tiger subspecies and only 1.742% different between tiger and leopard. Thus, such sequences represent molecular ‘fossils’ that can shed light on evolution of the mitochondrial genome and may be the most appropriate outgroup for phylogenetic analysis. This is also proved by comparing the phylogenetic trees reconstructed using the D-loop sequence of snow leopard and the 287-bp Numts as outgroup.
pp 117-122 August 2006 Research Article
We report a genetic diversity study of Kherigarh cattle, a utility draught-purpose breed of India, currently declining at a startling rate, by use of microsatellite markers recommended by the Food and Agriculture Organization. Microsatellite genotypes were derived, and allelic and genotypic frequencies, heterozygosities and gene diversity were estimated. A total of 131 alleles were distinguished by the 21 microsatellite markers used. All the microsatellites were highly polymorphic, with mean (±s.e.) allelic number of 6.24 ±1.7, ranging 4–10 per locus. The observed heterozygosity in the population ranged between 0.261 and 0.809, with mean (±s.e.) of 0.574 ±0.131, indicating considerable genetic variation in this population. Genetic bottleneck hypotheses were also explored. Our data suggest that the Kherigarh breed has not experienced a genetic bottleneck in the recent past.
pp 123-131 August 2006 Research Article
The morphological, yield, cytological and molecular characteristics of bread wheat X tritordeum F1 hybrids (2n =6x = 42; AABBDHch) and their parents were analysed. Morphologically, these hybrids resembled the wheat parent. They were slightly bigger than both parents, had more spikelets per spike, and tillered more profusely. The hybrids are self-fertile but a reduction of average values of yield parameters was observed. For the cytological approach we used a double-target fluorescencein situ hybridization performed with total genomic DNA fromHordeum chilense L. and the ribosomal sequence pTa71. This technique allowed us to confirm the hybrid nature and to analyse chromosome pairing in this material. Our results showed that the expected complete homologous pairing (14 bivalents plus 14 univalents) was only observed in 9.59% of the pollen mother cells (PMCs) analysed. Some PMCs presented autosyndetic pairing of Hch and A, B or D chromosomes. The average number of univalents was higher in the wheat genome (6.8) than in the Hch genome (5.4). The maximum number of univalents per PMC was 20. We only observed wheat multivalents (one per PMC) but the frequency of trivalents (0.08) was higher than that of quadrivalents (0.058). We amplified 50 RAPD bands polymorphic between the F1 hybrid and one of its parents, and 31 ISSR polymorphic bands. Both sets of markers proved to be reliable for DNA fingerprinting. The complementary use of morphological and yield analysis, molecular cytogenetic techniques and molecular markers allowed a more accurate evaluation and characterization of the hybrids analysed here.
pp 133-139 August 2006 Research Article
We have previously reported correction of severe leaf chlorosis in the cytoplasmic male sterile Ogura (also called Ogu)Brassica juncea line carrying Ogura cytoplasm by plastid substitution via protoplast fusion. Two cybrids obtained from the fusion experiment, Og1 and Og2, were green and carried the plastid genome ofB. juncea cv. RLM198. While Og1 displayed normal flower morphology comparable to that of its euplasmicB. juncea counterpart except for sterile anthers, Og2 retained homeotic-like floral modification of stamens to petal-like structures and several other floral deformities observed in the chlorotic (Ogu)B. juncea cv. RLM198 (or OgRLM). With respect to the mitochondrial genome, Og1 showed 81% genetic similarity to the fertile cultivar RLM while Og2 showed 93% similarity to OgRLM. In spite of recombination and rearrangements in the mitochondrial genomes in the cybrids, expression patterns of 10 out of 11 mitochondrial genes were similar in all the three CMS lines; the only exception wasatp6, whose expression was altered. While Og1 showed normalatp6 transcript similar to that in RLM, in Og2 and OgRLM weak expression of a longer transcript was detected. These results suggest that the homeotic-like changes in floral patterning leading to petaloid stamens in Og2 and OgRLM may be associated with aberrant mitochondrial gene expression.
pp 141-145 August 2006 Research Note
pp 147-151 August 2006 Research Note
pp 153-156 August 2006 Research Note
pp 157-160 August 2006 Research Note
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