Towards teaching for an integrated understanding of trait formation: an analysis of genetics tasks in high school biology textbooks

ABSTRACT

This paper reports on findings from an analysis of trait-formation tasks in the genetic sections of high school biology textbooks. Drawing on studies exploring a range of problems in students’ explanations of trait formation, we investigated trait-formation tasks and analysed their potential for knowledge integration and multi-level mechanistic reasoning. Among the 216 trait-formation tasks, 39 tasks (18%) were classified as integrative tasks addressing the relationships between genes, proteins and traits. The remaining 177 tasks (82%) were non-integrative tasks addressing selected aspects of the relationship between genes and proteins alone, respectively the relationship between proteins and traits alone. Among the non-integrative tasks, 64% addressed the molecular level alone and thus did not encourage students to address the higher levels of biological organisation. 13% of the non-integrative tasks (n = 23) and 5% of the integrative tasks (n = 2) addressed the role of the environment in trait formation. The findings are related to three main arguments from the genetics literature, concerning knowledge integration and multi-level mechanistic reasoning. As educational implications, we recommend that biology educators make use of integrative tasks to foster students’ understanding of trait formation from an integrated model connecting genes, proteins, environmental factors and traits to overcome gene-centred and gene-deterministic beliefs.     

Tissue-based assay for ornithine decarboxylase to identify patients likely to respond to difluoromethylornithine.

In a previous publication, we showed that a clinical trial of DL-alpha-difluoromethyl ornithine (DFMO), in combination with PCV (procarbazine, CCNU, vincristine) increased survival of patients with anaplastic gliomas (WHO III) but not glioblastoma multiforme (WHO IV). We believe that treatment outcome (survival) is inversely related to tumor ornithine decarboxylase (ODC) levels. To prove this, we needed to develop an assay to quantify ODC levels in formalin-fixed tumor tissues, which would enable a retrospective study of tumor biopsy specimens from the landmark clinical trial. We developed an assay using a specific polyclonal antibody coupled to an Alexa fluorescent dye. Transgenic MHC-ODC mice with differing levels of ODC in heart muscle were used to establish the relationship between mean gray-scale intensity and enzymatic ODC activity. We found a direct relationship between mean gray-scale intensity of the ODC antibody coupled to Alexa 647 dye and enzymatic activity. Preliminary analysis of a human glioma tissue array shows that tumor-specific variations in levels of ODC can be semiquantitated. We show that mean gray-scale intensity of astrocytoma:glioblastoma is 1:6 and of anaplastic astrocytoma:glioblastoma is 1:4. We also compared the intensity of antibody to Ki67 coupled with phycoerythrin simultaneously in cells but failed to see a relationship that crossed histologies. We conclude that we can measure levels of ODC in formalin-fixed tumor tissue using an antibody to ODC coupled to Alexa 647 dye, and this will enable us to conduct a future study to correlate survival of patients with gliomas of different histologies treated with DFMO to tumor ODC levels.     

Mineral and trace element research in goats: A review

The long term studies with dairy goats on the effects of deficient semisynthetic feeding rations in one of 16 elements as reported in the annual proceedings of the Workshops on Minerals and Trace Elements and the International Trace Element Symposia by the University of Jena, Germany, since 1975 until today were reviewed. The development of the complex semisynthetic ration system was particularly important as it enabled to produce significant deficiencies of single elements in long term replicated studies and their interactions with other elements. The studies focused mainly on determining deficiency levels for each of the 16 elements, identifying deficiency symptoms and reasons for them, and establishing evidence for essentiality of the elements according to 7 criteria. Large amounts of analytical data were accumulated showing the changes in organ and tissue contents of the elements under study at normal and deficient levels, and their relation to impaired reproductive efficiency, growth, milk production, health, and mortality of goats and their kids. Histological sections of organs also showed their ultrastructural changes due to the elemental deficiencies. Most element deficiencies caused reproductive failures, reduced growth and milk production, but high mortality, while the control goats thrived on their semisynthetic but sufficient ration, attesting to its completely correct biological value. The identification of the reliable “indicator” organs and tissues for the diagnosis and detection of deficiency status of the specific elements in goats is of particular value to veterinary medicine and animal nutrition.     

Two Stage Sampling for Simultaneously Testing Main and Side Effects in Clinical Trials

In clinical trials for the comparison of two treatments it seems reasonable to stop the study if either one treatment has worked out to be markedly superior in the main effect, or one to be severely inferior with respect to an adverse side effect. Two stage sampling plans are considered for simultaneously testing a main and side effect, assumed to follow a bivariate normal distribution with known variances, but unknown correlation. The test procedure keeps the global significance level under the null hypothesis of no differences in main and side effects. The critical values are chosen under the side condition, that the probability for ending at the first or second stage with a rejection of the elementary null hypothesis for the main effect is controlled, when a particular constellation of differences in mean holds; analogously the probability of ending with a rejection of the null hypotheses for the side effect, given certain treatment differences, is controlled too. Plans “optimal” with respect to sample size are given.     

The roles of coastlines, people and fire in the development of heathlands in northeast Tasmania

Abstract. Pollen analysis of a core taken from a reed marsh in northeastern Tasmania near Bass Strait highlights the interplay between climatic changes, sea level rises and the effects of Aborigines during the Holocene. Prior to 10,000 bp the region formed part of the Bassian landbridge which connected Tasmania to the Australian mainland. Vegetation at that time was characterized by shrubby grasslands with a very sparse tree cover. After 9000 bp, Eucalyptus forests prospered until about 6000 bp. A combination of salt spray from a stabilizing mid-Holocene coast, the progressive effects of soil podsolization and burning by Aborigines, eventually favoured the replacement of grassy Eucalyptus forests by Allocasuarina with an increasingly heathy understorey. The treeless heaths dominated by dwarfed Allocasuarina which presently dominate the area are regarded as part of a degradation sequence in which the above factors are implicated.     

Biokinetics of lead in various organs of rats using radiotracer technique

Uptake, distribution, and elimination of lead in various organs of rats have been studied using a radiotracer technique. The elimination data for various organs, except whole blood, is fitted to a double-exponential function using a computer program. The biological half-lives along with the percent elimination of lead by two different decay modes in testis, epididymis, prostate, and seminal vesicles are being reported together with that in liver, kidney, blood, and whole body. It is evident from this study that the elimination of lead is limited for all the organs and permits lead accumulation in the bone, where it is stored and becomes almost unavailable for elimination. Lead levels in blood, testis, and femur of lead acetate-fed rats measured using atomic absorption spectroscopy have been correlated to the uptake of²¹⁰Pb in various organs.     

Pregnancy reduces noradrenaline but not neuropeptide levels in the uterine artery of the guinea-pig

Summary Using histochemical, immunohistochemical and biochemical techniques, noradrenaline-, neuropeptide Y-, vasoactive intestinal polypeptide-, substance P- and calcitonin gene-related peptide-containing nerve fibres were studied in the uterine artery of virgin, progesterone-treated and pregnant guinea-pigs. Morphological changes following hormone treatment or in pregnancy were also evaluated in a quantitative study on semithin sections of the uterine artery. In late pregnancy, the number of noradrenalinecontaining nerve fibres, which formed the densest plexus in virgin animals, was significantly decreased, a finding supported by a significant reduction in noradrenaline levels. This reduction was not mimicked by systemic progesterone treatment. In contrast, the innervation of the uterine artery by neuropeptide Y-containing nerve fibres was increased in pregnancy, while the other peptidergic nerves and peptide levels were unchanged after progesterone treatment and in pregnancy. These changes led to a predominance of innervation by neuropeptide Y- rather than noradrenaline-containing nerve fibres in late pregnancy. No morphological changes were detected following progesterone treament, but pregnancy led to a marked increase in the cross-sectional area of the vessel accompanied by an increase in the thickness of the media.     

Food level reaction norms in size-selected milkweed bugs (Oncopeltus fasciatus)

Abstract. 1. The hypothesis that the small size of nonmigratory milkweed bugs from Puerto Rico (relative to large migratory bugs from Iowa) might be an adaptation to low food levels was tested with bugs selected for large and small size as the consequence of positive genetic correlation between body size and wing length. The test involved examining reaction norms of life history traits to different food levels.
2. When nymphs were reared on 3 milkweed seeds per nymph from hatch to adult eclosion, large bugs were adversely affected with only 50% and 60% in each of two replicates reaching adulthood. Control (unselected) and small bugs, however, were unaffected at this food level. None of the lines was affected at levels of 6 and 12 seeds per nymph.
3. When adults were reared from eclosion on 12, 18 or 24 milkweed seeds per bug, large bugs were adversely affected relative to control and small bugs at all three food levels. At each food level fewer large bugs produced eggs than either small or control bugs which did not differ.
4. The evidence from the food level reaction norms suggests that larger bugs will be selected against during periods of food shortage of the sort likely to occur in Puerto Rico.     

High trophic level feedbacks on global ocean carbon uptake and marine ecosystem dynamics under climate change

Despite recurrent emphasis on their ecological and economic roles, the importance of high trophic levels (HTLs) on ocean carbon dynamics, through passive (fecal pellet production, carcasses) and active (vertical migration) processes, is still largely unexplored, notably under climate change scenarios. In addition, HTLs impact the ecosystem dynamics through top-down effects on lower trophic levels, which might change under anthropogenic influence. Here we compare two simulations of a global biogeochemical–ecosystem model with and without feedbacks from large marine animals. We show that these large marine animals affect the evolution of low trophic level biomasses, hence net primary production and most certainly ecosystem equilibrium, but seem to have little influence on the 21st-century anthropogenic carbon uptake under the RCP8.5 scenario. These results provide new insights regarding the expectations for trophic amplification of climate change through the marine trophic chain and regarding the necessity to explicitly represent marine animals in Earth System Models.