首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Mendel was accused by Fisher that his observed data, which corresponded to expectations, were too good to be true, and, further, that Mendel, growing only 10 plants per offspring, disregarded in his genotypical analysis the loss of recessives by assuming a ratio of 1:2 instead of 1.1126:1.8874. In contrast, it is proposed here that all chi-square statistics of genetic segregations fall short because the variance of genetic segregations is smaller and not of a binomial type as assumed. Furthermore, this variance and the corresponding chi-square statistics are not homogeneous in different segregation types. Consequently, it is not possible to summarize the different chi-square statistics as Fisher did. It is only in this way that he was able to obtain his unrealistic result (a probability of "seven times in 100,000 cases"). Regarding Fisher's second accusation, it should be taken into account that Mendel selected his 10 plants from offspring with a finite and not an infinite number of entities. Although this number is different from offspring to offspring, the average number is about 30. This means that the loss of recessives must be calculated by using a hypergeometric and not a binomial model as Fisher did. Consequently, the real deviation from the 1:2 ratio can be disregarded.  相似文献   

2.
In the history of zoology the English anatomist Morrison Watson (1845–1885) is considered to be the discoverer of the masculinized sexual organs of the spotted hyena. Beginning in 1877, Watson had published a series of anatomical studies on the spotted hyena (Watson, 1877, 1878, 1881, Watson and Young, 1879), in which he, in which he for the first time made public the anatomical peculiarities of the female spotted hyena’s genitalia. This scientific achievement is well documented. But now we can also state that a hundred years before Watson the Dutch amateur zoologist Robert Jacob Gordon (1743–1795), while serving in the Scots Brigades at the Cape of Good Hope, had already made the same discovery and merely unfortunate personal circumstances prevented publication. During his stay at the Cape, Gordon had studied spotted hyenas intensively and recorded his observations in accurate drawings and comments. These drawings have been preserved as part of a large collection of animal drawings entitled Gordon Atlas. With his discovery, Gordon actually was the first to provide empirical evidence of a “curious and inexplicable case of dimorphism” (Darwin on a beetle) in mammalians, long before étienne Geoffrey Saint-Hilaire (Cours de l’histoire naturelle des mammifères, 1829) started examining masculinized sexual organs in the mole or Darwin recognized the importance of sexual dimorphism (Descent of Man, 1871). In this paper we reproduce for the first time all hyena drawings from the Gordon Atlas, including Gordon’s handwritten notes in the margins in the original Dutch and in translation. Additionally, we briefly delineate the knowledge about the South African spotted hyena in Gordon’s time and indicate that we doubt Watson’s explanation for the age-old confusion about the hyena.  相似文献   

3.
4.
5.
6.
Leprosy was a common and dreaded disease in the Danish Middle Ages (AD 1050-1536). Starting in the second half of the 13th century, leprosaria were established in many Danish towns and cities. In the city of Odense (on the island of Funen, Denmark), the cemetery of the leprosarium was totally excavated, and four nonleprosarium medieval and early modern cemeteries have been partly excavated. This paper explores the frequency of leprosy in the nonleprosarium cemeteries in Odense, and looks for evidence of selective exclusion from the ordinary population. The analyses are based on 733 skeletons from four cemeteries in Odense: the Gray Friars monastery, St. Albani parish church, St. Knuds cathedral, and Black Friars monastery. Seven lesions are scored and, based on known epidemiological properties (i.e., specificity and sensitivity) of these lesions, scores were transformed to statistics characterizing an individual's risk of having suffered from leprosy. This statistical approach remains of primary theoretical value, pending confirmation by independent research groups at other sites. Prevalence of the skeletal manifestation of leprosy at death varied between 0-17% among the different cemeteries in Odense. The highest prevalence was seen in cemeteries with many burials before AD 1400. It is estimated that before AD 1400, between 14-17% of those buried in the nonleprosarium cemeteries suffered from leprosy. In all nonleprosarium cemeteries, there was evidence for selective exclusion of people with facial leprosy lesions. For a short period just up to AD 1300, the cemetery of the Odense leprosarium had, on average, more than 20 yearly burials. The establishment of the leprosarium was followed within a relatively short period by a dramatic decline in the number of sufferers of leprosy in the nonleprosarium cemeteries. The number of yearly burials in the leprosarium cemetery also declined rapidly during the 14th century. The present analyses do not permit conclusions about the reasons for this decline in leprosy prevalence.  相似文献   

7.
8.
9.
10.
The importance of the radiolysis of water in irradiation of biological systems has motivated considerable theoretical and experimental work in the radiation chemistry of water and aqueous solutions. In particular, Monte–Carlo simulations of radiation track structure and non-homogeneous chemistry have greatly contributed to the understanding of experimental results in radiation chemistry of heavy ions. Actually, most simulations of the non-homogeneous chemistry are done using the Independent Reaction Time (IRT) method, a very fast technique. The main limitation of the IRT method is that the positions of the radiolytic species are not calculated as a function of time, which is needed to simulate the irradiation of more complex systems. Step-by-step (SBS) methods, which are able to provide such information, have been used only sparsely because these are time consuming in terms of calculation. Recent improvements in computer performance now allow the regular use of the SBS method in radiation chemistry. In the present paper, the first of a series of two, the SBS method is reviewed in detail. To these ends, simulation of diffusion of particles and chemical reactions in aqueous solutions is reviewed, and implementation of the program is discussed. Simulation of model systems is then performed to validate the adequacy of stepwise diffusion and reaction schemes. In the second paper, radiochemical yields of simulated radiation tracks calculated by the SBS program in different conditions of LET, pH, and temperature are compared with results from the IRT program and experimental data.  相似文献   

11.
Melville J. Herskovits (1895–1963) is widely regarded as the founder of Afro‐American anthropology. From the late 1920s to the early 1940s, he and his wife Frances produced an impressive body of research materials and scholarly publications on African and Afro‐American cultures, ‘virtually ignored among these materials is some 4,000 feet of motion picture footage and thousands of still photographs. This paper discusses Herskovits’ interest in using film records for studying body movement, gestures, and patterns of expressive behavior as persistent elements of the African heritage in the New World. The construction and style of imaging in two of his edited films is also discussed in relation to Herskovits’ scholarship and social and intellectual factors which prevailed at the time.  相似文献   

12.
13.
14.
15.
16.
17.
18.
19.
20.
R. Lespinasse 《Genetica》1985,66(2):151-151
Comment on the article ‘The B-chromosomes of Locusta migratoria I. Detection of negative correlation between mean chiasma frequency and the rate of accumulation of the B's; a reanalysis of the available data about the transmission of these B-chromosomes’ — Some critical remarks on the said article (published in Genetica 64: 155–164, 1984) are presented.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号