Over the past several decades, there has been a tremendous growth in our understanding of genetic phenomena and the intricate and complicated mechanisms that mediate genetic effects. Given the complexity of content in modern genetics and the inadequacy of current instructional methods and materials it seems that a more coherent and extensive approach to teaching modern genetics is needed. Learning progressions provide such an approach by describing the learning of core concepts in a domain as it unfolds over multiple grades and grade bands. In this paper we suggest a learning progression for modern genetics that spans grades 5-10. We describe the learning progression in terms of three key aspects of teaching and learning modern genetics: (1) the big ideas in modern genetics, and the knowledge and abilities that students should master by the end of compulsory education; and (2) the progression of learning that students are expected to make over several grades; and (3) the identification of learning performances and development of assessments for the proposed progression. We conclude by identifying the implications for instruction and research that stem from our analysis of the research base in genetics education, and our development of a theoretical progression for learning the big ideas in modern genetics. ß
In this study the direct involvement of cadherins in adhesion-mediated growth inhibition was investigated. It is shown here that overexpression of N-cadherin in CHO cells signi®cantly suppresses their growth rate. Interaction of these cells and two additional ®broblastic lines with synthetic beads coated with N-cadherin ligands (recombinant N-cadherin ectodomain or speci®c antibodies) leads to growth arrest at the G1 phase of the cell cycle. The cadherin-reactive beads inhibit the entry into S phase and the reduction in the levels of cyclindependent kinase (cdk) inhibitors p21 and p27, following serum-stimulation of starved cells. In exponentially growing cells these beads induce G1 arrest accompanied by elevation in p27 only. We propose that cadherinmediated signaling is involved in contact inhibition of growth by inducing cell cycle arrest at the G1 phase and elevation of p27 levels.
ABSTRACT:Interest is a powerful motivator; nonetheless, science educators often lack the necessary information to make use of the power of student-specific interests in the reform process of science curricula. This study suggests a novel methodology, which might be helpful in identifying such interests-using children's self-generated questions as an indication of their scientific interests. In this research, children's interests were measured by analyzing 1555 science-related questions submitted to an international Ask-A-Scientist Internet site. The analysis indicated that the popularity of certain topics varies with age and gender. Significant differences were found between children's spontaneous (intrinsically motivated) and school-related (extrinsically motivated) interests. Surprisingly, girls contributed most of the questions to the sample; however, the number of American girls dropped upon entering senior high school. We also found significant differences between girls' and boys' interests, with girls generally preferring biological topics. The two genders kept to their stereotypic fields of interest, in both their school-related and spontaneous questions. Children's science interests, as inferred from questions to Web sites, could ultimately inform classroom science teaching. This methodology extends the context in which children's interests can be investigated. Century, 2000) states that "we are failing to capture the interest of youth for scientific and mathematical ideas." Indeed, many students find standard science curricula largely out of touch with their personal interests, a factor which contributes to the low number of students pursuing advanced science and mathematics courses in high school, and going on to choose scientific careers (Millar & Osborne, 1998). Adolescents' decisions about the contents and directions of their educational training have been found to be influenced to a high degree by the topic-related interests they developed in the preceding years (Krapp, 2000).Organizations, including the National Research Council (1996) and the American Association for the Advancement of Science (1993), have proposed that science curricula taught at a secondary-school level should provide a common basis of knowledge while addressing the particular needs and interests of students. However, educators lack the necessary information and tools to guide modifications that could make use of the power of student-specific interests in improving those students' individualized learning and competency in scientific subjects.The issue of students' interests may also be viewed in the context of the pupil's voice in the education movement (Burke & Grosvenor, 2003;Economic and Social Research Council, 2004;Mirta, 2004;Whitehead & Clough, 2004). Until recently, the pupil's voice had been marginalized or neglected by educational researchers. The student was regarded as an object of study but not as someone who could make an informed judgment on what should be taught in school science courses (Jenkins & Nelson, 20...
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