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991.
To evaluate the effect of balancing selection and intragenic recombination (or gene conversion) at six individual HLA loci, synonymous nucleotide diversity in different exon groups is examined within (πw) and between (πb) allelic lineages that may be defined by either serological or DNA sequence differences. Both π values are high in exons
which encode for the peptide binding region (PBR) and tend to decrease in other exons. The value of πw is significantly smaller than that of πb in any exon of any locus. However, even πw is much greater than nucleotide diversity at non-HLA loci. These observations provide additional strong evidence for the operation of balancing selection in PBR-encoding exons
and its indirect effects on polymorphism at linked neighboring regions. It appears that allelic lineages have generally evolved
in isolation but the linkage relationships within and between exons are incomplete throughout the long evolutionary history.
To quantify intragenic recombination and account for the large discrepancy between the HLA and non-HLA diversity, a population genetics model is analyzed with special reference to the evolution of modern humans. The analysis
suggests that the recombination rate between two sites 1000 base pairs apart is about 10–5 per generation and that the effective size of human populations (equivalent roughly to the number of breeding individuals
in a randomly mating population) has dropped from 105 to 104 in most of the Quaternary. One possibility for this reduction is discussed.
Received: 11 August 1997 / Revised: 8 October 1997 相似文献
992.
The per capita home range area of Japanese macaques,Macaca fuscata, is significantly smaller in evergreen forest than in deciduous forest, though a corresponding difference in food resource
utilization patterns has never been described. The present study compared the home range utilization pattern of Japanese macaques
living in two habitats: the Yakushima population inhabits an evergreen forest, while the Kinkazan population inhabits a deciduous
forest. We found that in the Yakushima population, (1) food density was higher; (2) inter-feeding bout sites distance was
shorter; (3) daily travel distance was shorter; (4) home range size was smaller; and (5) the unit value of the main home range
was higher, than in the Kinkazan population. Yakushima groups utilized a small home range area intensively, compared to Kinkazan
groups. We also found that a Yakushima group shared 24% of its main home range with neighboring groups, though a Kinkazan
group shared only 10% with other groups. It is supposed that food distribution affects daily ranging pattern, and ultimately
the social relationships between groups in Japanese macaques. 相似文献
993.
G. P. Gill C. F. Harvey R. C. Gardner L. G. Fraser 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(3):439-445
Two sex-linked random amplified polymorphic DNA (RAPD) markers identified from Actinidia chinensis were converted into sequence-characterised amplified regions (SCARs) for the large-scale screening of Actinidia breeding populations. Initial SCAR primers converted one RAPD (SmX) into a dominant marker, but the other (SmY), which was
potentially more useful because of its linkage to the male determining ‘Y’ locus, failed to retain polymorphism. This difficulty
was overcome by cloning and sequencing the alternate ‘allele’ from female plants, and then designing ‘allele’-specific primers
that utilised nucleotide differences between the sexes. Using a quick squash-blot method of DNA extraction, the SCAR primers
were tested in 120 A. chinensis plants to determine their gender. The system is now in use for large-scale screening of seedling populations in the Actinidia breeding programme. The sex-linked SCAR primers also functioned with plants from some other geographically separate accessions
of A. chinensis and with plants in the closely related polyploid species A. deliciosa, but did not amplify a sex-linked band in more distantly related species of Actinidia.
Received: 27 December 1997 / Accepted: 5 March 1998 相似文献
994.
Takatoshi Ueno 《Journal of Insect Behavior》1998,11(6):811-821
Sex allocation by the polyphagous solitary pupal parasitoid wasp Pimpla luctuosa Smith to a small host species, Galleria mellonella (L.), and a large host species, Mamestra brassicae L., was investigated to test whether female wasps responded to hosts of different sizes across different host species. In the experiments, both host species were presented to each test female wasp. Primary and secondary sex ratio experiments revealed that female wasps laid more female eggs in larger pupae of each host species, indicating that female wasps recognized size differences within host species. The wasp sex ratio (male ratio) from M. brassicae, however, was much higher than that expected on the basis of the sex ratio curve from different-sized G. mellonella. Larger hosts of each host species yielded larger wasps, indicating that the host size estimation by female wasps across different host species was incomplete or was not simple. These results suggested that P. luctuosa evaluated host size not only by physical measures such as dimension but also by other unknown measures. A possible explanation for the adaptiveness of different sex ratio responses by Pimpla luctuosa to different host species was discussed. 相似文献
995.
The relationship between fluctuating asymmetry (FA) and mating success was studied within males of the sphragis-baring butterfly Luehdorfia japonica, which were collected at various periods during their mating season. FA was measured on the forewing and hindwing radius lengths of male butterflies. Mating frequency of males was estimated by assessing the degree of scale loss from their claspers. Males consume scales and use them to form sphragis on the female abdomen during copulation, sealing the ostium bursa for life. Age of males was scored as wing age 0 to 4 according to the wearing of the wing. FA was negatively correlated with mating frequency but positively correlated with wing age, and average FA decreased with mating season. As females have little chance to express mate choice, it is likely that FA is an indicator of male viability: symmetrical males live longer and/or fly more actively, resulting in a higher lifetime mating success compared to asymmetrical males. 相似文献
996.
Denis D.G. Mater Annabelle L. Zgoda Jean-Noél Barbotin Daniel Thomas 《Biotechnology Techniques》1998,12(11):811-814
D.D.G.M. and A.L.Z each contributed to 50%.Due to the lack of suitable chromosomal markers, antibiotics could not be used to select transconjugant clones arising from matings between two Pseudomonas strains. As an alternative, a method based on the specificity of a lytic bacteriophage for the recipient strain was used successfully. © Rapid Science Ltd. 1998 相似文献
997.
998.
Daniel Pauly 《Reviews in Fish Biology and Fisheries》1998,8(3):307-334
The extension into tropical areas of Beverton and Holt's yield per recruit approach for stock assessment represents a straightforward case of normal science, the common Kuhnian counterpart to his much rarer paradigm shifts. It is shown that the normal science which, in recent decades, has led to new methods for estimating growth, mortality and other statistics required for yield per recruit analyses in data-sparse environments, has not only enriched fisheries science and aquatic biology as a whole, but has also contributed to identify the limitations of the single-species research programme originally defined by Beverton and Holt. The most likely prospect for that programme, in the tropics and elsewhere, is to become a component of the multispecies, or rather ecosystem approach that is emerging, and to which Beverton and Holt will have contributed many of the concepts, and much of the rigour. 相似文献
999.
1000.
种群内个体大小不整齐性是种群数量结构的主要指标。本文研究了不同水分条件下,3个品种春小麦种群个体大小不整齐性的建立及变化规律。对春小麦种群不整齐性的遗传学分析表明:遗传结构与随机环境修饰对种群数量结构形成的相对重要性,因水分条件不同而异。种群不整齐性在自然选择中的作用可用下列简单模型表示:CSo=SH×hSH2 CSo:自然选择强度;SH:大小不整齐性;hSH2:不整齐性的遗传力。 相似文献