The chromosome number in humans: a brief history

Following the rediscovery of Mendel's work in 1900, the field of genetics advanced rapidly. Human genetics, however, lagged behind; this was especially noticeable in cytogenetics, which was already a mature discipline in experimental forms in the 1950s. We did not know the correct human chromosome number in 1955, let alone were we able to detect a chromosomal abnormality. In 1956 a discovery was reported that markedly altered human cytogenetics and genetics. The following is an analysis of that discovery.     

Armin von Tschermak-Seysenegg (1870–1952): Physiologist and Co-‘Rediscoverer’ of Mendel’s laws

The ‘rediscovery’ of Mendel’s laws in 1900 was a turning point in modern research of heredity/genetics. According to the traditional view, adopted and fostered by many textbooks of genetics, Mendel’s principles were presented in the first half of 1900 simultaneously and independently by three biologists (H. de Vries, C. Correns, E. v. Tschermak-Seysenegg). Having thus laid the foundations of further development, the ‘rediscovery’ continues to attract considerable interest. Since the 1950s, however, serious questions arose concerning both the chronology and specific conceptual achievement of the scientists involved. Not only the independence but also parallelism was analysed in the context of individual research programmes of these three scholars. The youngest of them, Erich v. Tschermak-Seysenegg, was even excluded from the list of ‘rediscoverers’. The aim of this paper is to use new archival evidence and approximate the contribution of the physiologist and ophthalmologist Armin von Tschermak-Seysenegg (1870–1952) to the events of 1900 and 1901.     

On the internal dynamics of Mendelian genetics

This paper offers a revisionist account of the development of Mendelian genetics, focusing on the 'problem of the gene', 1900-1930. I examine conflicting claims about the composition, location, and action of genes posed by Bateson, the Morgan group, and Goldschmidt. Their research programs focused on different phenotypes and were based on different assumptions about the nature of genes. The problem of the gene transcended such specific research programs, but their findings had to be taken into account to solve it. The need to resolve conflicting claims drove Mendelian geneticists to exploit the resources and invade the turf of other disciplines in their search for a sound characterization of the gene. The problem of reconciling conflicting views greatly influenced the development of genetics and provided the stimulus for many of the discoveries made by geneticists from 1900 to 1940.     

Mendelian inheritance in Germany between 1900 and 1910. The case of Carl Correns (1864-1933)

Carl Correns (1864-1933) came to recognize Mendel's rules between 1894 and 1900 while trying to find out the mechanism of xenia, that is, the direct influence of the fertilizing pollen on the mother plant in maize and peas among other species. In this paper, I am concerned with the ten years of Correns' work after the annus mirabilis of 1900 until 1910, when the main outlines of the new science of genetics had been established. It is generally assumed that after 1900 Correns quickly began probing the limits of Mendelian inheritance, both as far as the explanatory force of formal transmission genetics and the generality of Mendel's laws are concerned. A careful examination of his papers however shows that he was much more interested in the scope of Mendelian inheritance than in its limits. Even his work with variegated Mirabilis plants, which historiographical folklore still presents as a result of Correns' growing interest in cytoplasmic inheritance, can be shown to have been conducted to corroborate just the opposite, namely, the validity of the nuclear paradigm. The paper will show that Correns' research results in those years (among them the Mendelian inheritance of sex in higher plants) were the outcome of a complex experimental program which involved breeding experiments with dozens of different species.     

William Bateson, human genetics and medicine

The importance of human genetics in the work of William Bateson (1861–1926) and in his promotion of Mendelism in the decade following the 1900 rediscovery of Mendel’s work is described. Bateson had close contacts with clinicians interested in inherited disorders, notably Archibald Garrod, to whom he suggested the recessive inheritance of alkaptonuria, and the ophthalmologist Edward Nettleship, and he lectured extensively to medical groups. Bateson’s views on human inheritance were far sighted and cautious. Not only should he be regarded as one of the founders of human genetics, but human genetics itself should be seen as a key element of the foundations of mendelian inheritance, not simply a later development from knowledge gained by study of other species.     

Research note: Genes on chromosomes: The conversion of Thomas Hunt Morgan

In the first decade of the twentieth century, the foundation for the science of genetics was set. In 1900, the data of Gregor Mendel were rediscovered. By 1915, a community of scientists accepted that there were entities on chromosomes that controlled the development of observable traits. During the intervening period, Thomas Hunt Morgan was one of the major skeptics regarding the chromosomal location of the genes. His acceptance may have been the turning point for the flowering of American genetics. This paper will discuss the reasons for Morgan's recalcitrance, his conversion to belief, and the nature of the scientific evidence that led to his acceptance.     

孟德尔豌豆基因克隆的研究进展及其在遗传学教学中的应用

150多年前, 孟德尔进行了豌豆7对相对性状的杂交试验, 发现了遗传学的两个基本规律。1900年, 孟德尔定律被重新发现以后, 人们从生理生化、细胞和分子水平等不同层次上对豌豆的这7个性状进行了深入研究。近年, 随着分子生物学技术的发展, 已有种子形状(R)、茎的长度(Le)、子叶颜色(I)和花的颜色(A)等4个性状的基因被克隆; 未成熟豆荚的颜色(Gp)、花的着生位置(Fa)和豆荚形状(V)的基因已被定位在各自的连锁群上。4个孟德尔基因的鉴定和克隆加深了人们对基因概念的理解：如基因功能的多样性、在分子水平上基因变异原因的多样性、显性和隐性的分子实质等。在遗传学教学中, 把孟德尔基因克隆和研究的最新进展介绍给学生, 在分子水平上诠释经典遗传规律, 有助于提高学生的学习兴趣, 帮助学生全面把握从形式遗传学到分子遗传学的内容和遗传学的发展方向。     

Rotifer genetics: integration of classic and modern techniques

Rotifer genetics has a long but sporadic history. There have been 4 major periods of research activity: (1) determining the environmental control of sexuality with inferences regarding genetics — early 1900's; (2) exploring the relationship between chromosome numbers and the rotifer life cycle — 1920's; (3) physiological and developmental genetics — 1960's; and (4) theoretical and experimental population genetics late 1970's. With newly developed molecular techniques, in conjunction with more traditional approaches, integration of these fields is beginning. Examples include investigation of gene expression involved in sexual reproduction by isolating glycoproteins responsible for mate recognition. Improvement of techniques for chromosome analysis has made it possible to verify haploidy in males and led to the discovery of polyploidy. The role of specialized proteins in the stress response is being elaborated with an accompanying search for the genetic elements which control them. Most recently the polymerase chain reaction (PCR) has been used to amplify ribosomal genes, and is a first step in using DNA sequences to define evolutionary relationships among the Rotifera.     

The singular fate of genetics in the history of French biology, 1900–1940

In this study we have examined the reception of Mendelism in France from 1900 to 1940, and the place of some of the extra-Mendelian traditions of research that contributed to the development of genetics in France after World War II. Our major findings are:

A gerontological cohort study of aged twins: the Osaka University Aged Twin Registry.

We describe subject recruitment and research results from the Osaka University Aged Twin Registry (OUATR). The research focus of OUATR is the genetic and environmental contributions to physical-cognitive-mental aging which we examined in Japanese twins in later adulthood. Within this large-scale registry (12,000 pairs) of oriental twins born between 1900 and 1935, approximately 10% of participants are MZ twins reared apart from early childhood. Two hundred and fifty pairs have had comprehensive medical examinations, including various blood chemical panels, lymphocyte subtests, WAIS (Wechsler Adult Intelligence Scale), and urine analysis. The future foci of this study are primarily on longevity, decline of cognitive functions with aging, bio-physiological functions, lifestyle and behavior genetics, and psycho-spiritual functions.     

Carl Correns' experiments with Pisum, 1896-1899

The circumstances under which classical genetics became established at the turn of the nineteenth century have become an integral part of the standard narrative on the history of genetics. Yet, despite considerable scholarly efforts, it has remained a matter of debate how exactly the so-called 'rediscovery' of Mendel's laws came about around 1900. In this situation, unpublished research records can be invaluable tools to arrive at a more substantial and more satisfying picture of the order of historical events. This paper makes extended use of the research protocols covering Carl Correns' hybridisation experiments with Pisum sativum between 1896 and 1899. The resulting reconstruction sketches the portrait of a scientist following a particular research question--xenia--struggling with his experimental material, and slowly building up an epistemic regime in which questions and observations could acquire a relevance which did not strike Correns when he first took note of them. The microhistorical gaze through the magnifying glass of research notes reveals the kind of delays that appear to be constitutive for empirically-driven thinking in general. The research notes of Correns help not only to make this point, they also display some of the intricacies and material peculiarities which characterise the experimental process of hybridisation and the particular type of inferences it allows one to make.     

Punnett's square

The origin and development of Punnett's Square for the enumeration and display of genotypes arising in a cross in Mendelian genetics is described. Due to R. C. Punnett, the idea evolved through the work of the 'Cambridge geneticists', including Punnett's colleagues William Bateson, E. R. Saunders and R. H. Lock, soon after the rediscovery of Mendel's paper in 1900. These geneticists were thoroughly familiar with Mendel's paper, which itself contained a similar square diagram. A previously-unpublished three-factor diagram by Sir Francis Galton existing in the Bateson correspondence in Cambridge University Library is then described. Finally the connection between Punnett's Square and Venn Diagrams is emphasized, and it is pointed out that Punnett, Lock and John Venn overlapped as Fellows of Gonville and Caius College, Cambridge. Copious illustrations are given.     

The past,present and future of gene targeting in Drosophila

The beginnings of Drosophila as a model organism reach far back into the 1900s to Thomas Hunt Morgan's first fly room. The success of this system for the study of genetics is closely linked to the fact that the fly is amenable to complex genetic manipulations so that random mutagenesis screens can be easily performed. Nonetheless, current advances in genomics and in our ability to predict protein function emphasize the importance of mutagenesis methods that are not random, but rather give the researcher control over how the gene is modified. Gene targeting in Drosophila, developed almost a decade ago, makes use of the organism's own DNA repair machinery to exchange genetic information between a chromosomal target and an exogenous template. Here we discuss available targeting methods and recent advances that facilitate repeated targeting and open the doors to routine allelic studies.     

Effect of covalent attachment of polyethylene glycol on immunogenicity and circulating life of bovine liver catalase.

Methoxypolyethylene glycols of 1900 daltons (PEG-1900) or 5000 daltons (PEG-5000) were covalently attached to bovine liver catalase using 2,4,6-trichloro-s-triazine as the coupling agent. Rabbits were immunized by the intravenous and intramuscular routes with catalase modified by covalent attachment of PEG-1900 to 43% of the amino groups (PEG-1900-catalase). The intravenous antiserum did not yield detectable antibodies against PEG-1900-catalase or native catalase, as determined by Ouchterlony and complement fixation methods, whereas the intramuscular antiserum contained antibodies to both PEG-1900-catalase and catalase. PEG-1900 did not react with either antiserum. Catalase was prepared in which PEG-5000 was attached to 40% of the amino groups (PEG-5000-catalase). This catalase preparation did not react with either antiserum. PEG-1900-catalase retained 93% of its enzymatic activity; PEG-5000-catalase retained 95%. PEG-5000-catalase resisted digestion by trypsin, chymotrypsin, and a protease from Streptomyces griseus. PEG-1900-catalase and PEG-5000-catalase exhibited enhanced circulating lives in the blood of acatalasemic mice during repetitive intravenous injections. No evidence was seen of an immune response to injections of the modified enzymes. Mice injected repetitively with PEG-5000-catalase remained immune competent for unmodieied catalase, and no evidence of tissue or organ damage was seen.     

Circadian rhythms of feeding, oviposition, and emergence of the boll weevil （Coleoptera： Curculionidae）

Circadian rhythm of feeding, oviposition, and emergence of boll weevil adults were determined at five different photophases （24, 14, 12, 10, and 0 hours） and a constant 27℃ temperature, 65% RH in the laboratory. Squares from Petri dishes, where they were exposed to boll weevil females, were removed and examined for feeding and oviposition punctures every 4 hours during daylight （0700-1900 h） and every 12 h at night （1900-0700 h） over eight consecutive days. Cohorts of randomly selected egg-punctured squares were sampled from ovipositing females at 0700, 1100, 1500, and 1900 during 24 hours and under different photophase treatments, and maintained in Petri dishes at 27 ＋ I℃, 65% RH. Dishes were observed twice daily （1900 and 0700 h） for adults emerging at day or night. Circadian rhythm of oviposition was not affected by the length of the photophase. The boll weevil has round-the-clock circadian rhythm of oviposition, with a daytime preference. We observed that 82.4%-86.0% of the boll weevil eggs were deposited between 0700 and 1900 h, and 14.0%-17.6% between 1900 and 0700 h during a 24-h period. Feeding of boll weevil females in photoperiods 24：0 h （complete light） and 0：24 h （complete darkness） did not significantly change between 0700-1900 h versus 1900-0700 h, while the d .ally cycle of light and darkness in other photoperiods significantly increased the feeding punctures from 0700-1900 compared with 1900-0700 h. The circadian rhythm of emergence depended significantly on the time of oviposition and the length of the photophase. Investigation of boll weevil circadian rhythm provides a better understanding of boll weevil ecology and reveals potential weak links for improving control technologies targeting their reproductive strategies.     

Comparison of sulfur concentrations within lake sediment profiles

Sediment cores from lakes in four regions (Adirondacks, Northern New England, Northern Great Lakes States, and Northern Florida) were analyzed for total S concentration. In all regions S concentrations in pre-1900 (1820–1900) sediment were similar and pre-1900 net sediment accumulation rates of S were not significantly different. Sulfur enrichment was greatest in Adirondack lake sediment (Big Moose L., Upper Wallface P., Queer L., and Deep L.), which had total post-1900 S accumulation of 1.1 to 7.4 times pre-1900 S accumulation; post-1900 net sediment accumulation rates of S were significantly greater than the other regions. Sediment from Maine (Little Long P. and Haystack P.) and Vermont (Mud P.) generally had lower S concentration than Adirondack sediments. Sulfur enrichment factors in these lakes ranged from 1.2 to 2.1. There was a positive correlation between contemporary limnetic sulfate concentration and post-1900 net sediment accumulation rates for Adirondack and Northern New England study lakes. Sediment from the Northern Great Lakes States region (McNearney, Andrus, Hustler L. and Dunnigan L.) had similar S concentration and distribution with depth to Northern New England sediment. In two Northern Florida lakes (Mirrow and Fore) sediment showed little variation in S concentration with depth, but L. Mary and L. Barco had higher S in deeper layers (30–55 cm). These different patterns of S distribution among lakes were attributed to differences in limnetic sulfate concentration, organic and inorganic sedimentation, and S diagenesis.     

Glutamate antagonists attenuate the action of NC-1900, a vasopressin fragment analog, on passive avoidance task performance in mice

To examine the relationship between glutamate receptors and the action of NC-1900 on a step-through passive avoidance (PA) task in mice, MK-801, an NMDA receptor blocker, and (S)-4-carboxyphenylglycine (4CPG), a group I metabotropic receptor antagonist, were administered intraventricularly (i.c.v.) singly or as co-injections. The i.c.v. injection of MK-801 (0.8 microg) or 4CPG (2 microg) decreased the latency on the PA task. NC-1900 (1 ng/kg, subcutaneously (s.c.)) alone prolonged the latency on the retention trial in the PA task. MK-801 (0.2 and 0.8 microg) or 4CPG (0.5 and 2 microg) significantly inhibited the action of NC-1900, while the s.c. injection of NC-1900 did not affect latency in mice that received i.c.v. co-injection of MK-801 and 4CPG at any of the doses tested. These results suggest that glutamate receptors participate in the action of NC-1900 on learning and memory in PA task performance.     

Facilitative effect of a novel AVP fragment analog, NC-1900, on memory retention and recall in mice

In order to determine the mechanism of action of a new AVP(4-9) analog, NC-1900, on memory processes, memory retention and retrieval tests were conducted in a step-through passive avoidance (PA) task in mice. The administration of NC-1900 facilitated memory retention and retrieval in the PA task through vasopressin1A (V1A) receptors but not V2 receptors. The effect of NC-1900 on memory retention test performance appeared to be due to activation of the protein kinase C (PKC) signaling pathway via V1A receptors; however, the modulation of PKC was not essential for the facilitative effect of the new peptide in the retrieval test. The facilitation of memory retrieval by NC-1900 may also be mediated by other non-PKC-dependent signaling pathways, such as the phospholipase C-inositol trisphosphate pathway.     

Post-colonization temporal genetic variation of an introduced fly, Rhagoletis completa

Evolutionary biologists have been puzzled by the success of introduced species: despite founder effects that reduce genetic variability, invasive species are still successful at colonizing new environments. It is possible that the evolutionary processes during the post-colonization period may increase the genetic diversity and gene flow among invasive populations over time, facilitating their long-term success. Therefore, genetic diversity and population structure would be expected to show greater temporal variation for successful introduced populations than for native populations. We studied the population genetics of the walnut husk fly, Rhagoletis completa, which was introduced into California from the Midwestern US in the early 1900s. We used microsatellites and allozymes to genotype current and historic fly populations, providing a rare perspective on temporal variability in population genetic parameters. We found that introduced populations showed greater temporal fluctuations in allele frequencies than native populations. Some introduced populations also showed an increase in genetic diversity over time, indicating multiple introductions had occurred. Population genetic structure decreased in both native and introduced populations over time. Our study demonstrates that introduced species are not at equilibrium and post-colonization processes may be important in ameliorating the loss of genetic diversity associated with biological invasions.