“The ‘Domestication’ of Heredity: The Familial Organization of Geneticists at Cambridge University, 1895–1910”

In the early years of Mendelism, 1900–1910, William Bateson established a productive research group consisting of women and men studying biology at Cambridge. The empirical evidence they provided through investigating the patterns of hereditary in many different species helped confirm the validity of the Mendelian laws of heredity. What has not previously been well recognized is that owing to the lack of sufficient institutional support, the group primarily relied on domestic resources to carry out their work. Members of the group formed a kind of extended family unit, centered on the Batesons’ home in Grantchester and the grounds of Newnham College. This case illustrates the continuing role that domestic environments played in supporting scientific research in the early 20th century.     

Limb outgrowth in the chick embryo induced by dissociated and reaggregated cells of the apical ectodermal ridge.

Mesodermal cores of the stage 19 chick leg bud were capped with an intact apical ectodermal ridge (AER) or with strips cut from centrifugal pellets formed from Pronase-dissociated AERs. They were then covered with embryonic back-skin ectoderm and grown as grafts to the somite region of a host embryo. Control mesoderms were capped with centrifugal aggregates of nonridge limb ectoderm or similarly treated back-skin ectoderm, with ethanol-killed AERs or with no ectodermal cells other than the enveloping back-skin ectoderm.Controls were vascularized slowly and atypically and showed little outgrowth, forming only proximal skeletal structures. Recombinants equipped with AER cells were vascularized more fully and promptly and began vigorous growth after brief delay, forming legs with all skeletal segments represented, including claw-tipped toes. The latter were arranged in anteroposterior order corresponding to the original polarity of the mesoderm.Histological sections of recombinants made with cytologically distinctive quail AERs reveal that the cap of ridge cells, whether initially intact or reaggregated beneath the back-skin envelope, undergo a period of reorganization, forming a typical AER at the apex of the chimeric appendage after 48 hr. Meanwhile vigorous growth of the recombinant continues.These results show that the AER can cooperate with nonlimb ectoderm in promoting the morphogenesis of successively more distal levels of the limb skeleton. They also show that dissociated ridge cells can reorganize a typical AER at the apex of the limb mesoblast, meanwhile exercising their inductive effect on it.     

黑嘴鸥种群的遗传分化与迁徙模式

用分子生物学方法研究了黑嘴鸥(Larus saundersi)种群的遗传结构和分化.对我国黑嘴鸥现存的3个地方种群50个样本的线粒体DNA控制区部分片段进行了序列测定,结合已公布的的两个韩国样本的序列,比对后所获得的550 bp的序列中,共发现49个变异位点,定义了37种线粒体单元型,其中仅1种为我国3个地方种群间共享单元型,多数为各地方种群内特有.我国3个地方种群内的单元型多样性和核苷酸多态性都很高;4个地方种群合并成一个大种群时, 其线粒体单元型多样性与核苷酸多样性仍很高,分别为0.974%±0.012%和0.510%±0.042%.进一步分析表明,4个地方种群间核苷酸歧异度在0.433%-0.585%之间,种群分化程度FST在-0.03176-0.48063之间,基因流Nm在1.03-33.79之间,平均遗传距离为0.0051±0.0011.UPGMA系统发生树及最大简约网络图表明, 黑嘴鸥的演化关系呈现星状辐射,单元型之间呈现一种混杂的分布格局,地方种群没有形成明显的系统地理结构.同时运用彩色旗标技术,初步掌握了4个地方种群迁徙规律.对比分子研究结果,验证了不同地方种群间的遗传分化与其迁徙模式基本一致,同时认为黑嘴鸥不同地方繁殖种群从越冬地返回繁殖地的过程中会发生交叉.最后,鉴于黑嘴鸥不同地方种群间的遗传分化不显著,其迁徙行为具有差异性,建议在保护和遗传管理中应分别对待.     

Breeding biology of Saunders’s tern (Sterna saundersi) in the Farasan Islands,Kingdom of Saudi Arabia

Saunders’s terns (Sternula saundersi) are a small, ground-nesting marine bird species that have a massive rearing range, including the shores and islands of Asia and Africa adjacent to the north Indian Ocean. Despite occupying a large breeding range, little is known about the breeding ecology of this species. This research explored aspects of Saunders’s terns’ breeding ecology and predation rate in 2013 on the Farasan Islands of Saudi Arabia. The outcomes confirm that the mean clutch size of a Saunders’s tern was 1.77 ± 0.08 (n = 31) eggs per clutch and the mean egg size was 31.05 × 23.15 mm. The results of this study show a remarkable relationship between clutch size and egg volume and length (p = .002, p = .004, respectively). Predation was the major reason for nest damage (62.5%). Evidence from cameras at nests showed that the predators of Saunders’s tern nests on the Farasan Islands were white-tailed mongoose (Ichneumia albicauda) and Egyptian vultures (Neophron percnopterus). This is the first study on the breeding ecology of Saunders’s terns, and it shows that predator control is essential to the existence of the species. The results of this study suggest that fencing some breeding sites may help to minimize human disturbance and decrease the risk of nest predation from mammalian predators. Further research is needed to compare the predation rates on the mainland and islands and to develop efficient strategies to conserve this ground-nesting species.     

Birnbaum–Saunders frailty regression models: Diagnostics and application to medical data

In survival models, some covariates affecting the lifetime could not be observed or measured. These covariates may correspond to environmental or genetic factors and be considered as a random effect related to a frailty of the individuals explaining their survival times. We propose a methodology based on a Birnbaum–Saunders frailty regression model, which can be applied to censored or uncensored data. Maximum‐likelihood methods are used to estimate the model parameters and to derive local influence techniques. Diagnostic tools are important in regression to detect anomalies, as departures from error assumptions and presence of outliers and influential cases. Normal curvatures for local influence under different perturbations are computed and two types of residuals are introduced. Two examples with uncensored and censored real‐world data illustrate the proposed methodology. Comparison with classical frailty models is carried out in these examples, which shows the superiority of the proposed model.