One of the unique insights provided by the growing number of fully sequenced genomes is the pervasiveness of gene duplication and gene loss. Indeed, several metrics now suggest that rates of gene birth and death per gene are only 10–40% lower than nucleotide substitutions per site, and that per nucleotide, the consequent lineage‐specific expansion and contraction of gene families may play at least as large a role in adaptation as changes in orthologous sequences. While gene family evolution is pervasive, it (...) may be especially important in our own evolution since it appears that the “revolving door” of gene duplication and loss has undergone multiple accelerations in the lineage leading to humans. In this paper, we review current understanding of gene family evolution including: methods for inferring copy number change, evidence for adaptive expansion and adaptive contraction of gene families, the origins of new families and deaths of previously established ones, and finally we conclude with a perspective on challenges and promising directions for future research. (shrink)

There is a constructive method to define a structure of simple k-cyclic Post algebra of order p, L p,κ, on a given finite field F, and conversely. There exists an interpretation Ф₁ of the variety V generated by L p,κ into the variety V) generated by F and an interpretation Ф₂ of V) into V such that Ф₂Ф₁ = B for every B ϵ V and Ф₁₂ = R for every R ϵ V). In this paper we show how we (...) can solve an algebraic system of equations over an arbitrary cyclic Post algebra of order p, p prime, using the above interpretation, Gröbner bases and algorithms programmed in Maple. (shrink)

Interaction between adults and infants by nature constitutes a strong powerasymmetry relationship. Based on the assumption that communicative practices with infants are inseparably intertwined with broader cultural ideologies of good child care, this paper will contrast how parents in two distinct socio-cultural communities deal with power asymmetry in interactions with 3-months old infants. The study consists of a microanalysis of videotaped free play mother-infant interactions from 20 middle class families in Muenster, Germany and 20 traditional farming Nso families in Kikaikelaki, (...) Cameroon. Analysis followed a discursive psychology approach. The focus of analysis is on how mothers handle and negotiate power-distance in these interactions and what discursive strategies they draw on. Mothers in both groups used various forms of directives and control strategies. The Muenster mothers, however, mainly used mitigated directives that can be seen as strategies to reduce the competence gap between mother and child, while the Nso mothers mainly used upgraded directives to stress the hierarchical discrepancy between mother and child. The different strategies are discussed in light of the prevailing broader cultural ideologies and the normative orientations that they reflect. Finally, the findings are discussed with regard to possible developmental consequences of these distinct cultural practices for the child. Keywords: power-asymmetry; mother-infant interaction; discursive psychology; culture; Nso farmers; Muenster middle class families. (shrink)

Interaction between adults and infants by nature constitutes a strong powerasymmetry relationship. Based on the assumption that communicative practices with infants are inseparably intertwined with broader cultural ideologies of good child care, this paper will contrast how parents in two distinct socio-cultural communities deal with power asymmetry in interactions with 3-months old infants. The study consists of a microanalysis of videotaped free play mother-infant interactions from 20 middle class families in Muenster, Germany and 20 traditional farming Nso families in Kikaikelaki, (...) Cameroon. Analysis followed a discursive psychology approach. The focus of analysis is on how mothers handle and negotiate power-distance in these interactions and what discursive strategies they draw on. Mothers in both groups used various forms of directives and control strategies. The Muenster mothers, however, mainly used mitigated directives that can be seen as strategies to reduce the competence gap between mother and child, while the Nso mothers mainly used upgraded directives to stress the hierarchical discrepancy between mother and child. The different strategies are discussed in light of the prevailing broader cultural ideologies and the normative orientations that they reflect. Finally, the findings are discussed with regard to possible developmental consequences of these distinct cultural practices for the child. Keywords: power-asymmetry; mother-infant interaction; discursive psychology; culture; Nso farmers; Muenster middle class families. (shrink)