Origin of a Giant Sex Chromosome

Chromosome size and morphology vary within and among species, but little is known about the proximate or ultimate causes of these differences. Cichlid fish species in the tribe Oreochromini share an unusual giant chromosome that is ∼3 times longer than the other chromosomes. This giant chromosome functions as a sex chromosome in some of these species. We test two hypotheses of how this giant sex chromosome may have evolved. The first hypothesis proposes that it evolved by accumulating repetitive elements as recombination was reduced around a dominant sex determination locus, as suggested by canonical models of sex chromosome evolution. An alternative hypothesis is that the giant sex chromosome originated via the fusion of an autosome with a highly repetitive B chromosome, one of which carried a sex determination locus. We test these hypotheses using comparative analysis of chromosome-scale cichlid and teleost genomes. We find that the giant sex chromosome consists of three distinct regions based on patterns of recombination, gene and transposable element content, and synteny to the ancestral autosome. The WZ sex determination locus encompasses the last ∼105 Mb of the 134-Mb giant chromosome. The last 47 Mb of the giant chromosome shares no obvious homology to any ancestral chromosome. Comparisons across 69 teleost genomes reveal that the giant sex chromosome contains unparalleled amounts of endogenous retroviral elements, immunoglobulin genes, and long noncoding RNAs. The results favor the B chromosome fusion hypothesis for the origin of the giant chromosome.

Artificial fusion: The curious case of Macaronic Latin

Aims and Objectives/Purpose/Research Questions: The present paper aims to situate Macaronic Latin, a peculiar type of linguistic mixture that was used in literary works in early modern Europe, within the context of phenomena such as code-switching and borrowing, as well as mixed and constructed languages. The main objective is to see whether and how it can be compared to various instances of linguistic structures originating from more than one source language. Design/Methodology/Approach: After a description of its historical background and sociolinguistic features, main linguistic traits of Macaronic Latin are sketched and, finally, compared to other language contact phenomena, with particular reference to the fusion hypothesis. Data and Analysis: The main data for the analysis are sixty samples from macaronic works belonging to eleven language pairs. The analysis shows that mixed words in Macaronic Latin have properties of both borrowings and loans, being very similar to nonce formations. When compared to mixed and constructed languages, Macaronic Latin shows peculiarities that set it apart from either group. Findings/Conclusions: Although individual structural aspects of Macaronic Latin align its individual aspects with various outcomes of linguistic contact, the sociolinguistic pattern of its creation and later development make it a rather untypical case of linguistic mixing. Originality: Latin served as the main language of learned communication in medieval and early modern Europe; yet, this paper is the first study devoted to putting it in the context of mixed language debate. Significance/Implications: The study suggests that the preservation of the widespread use of a language with no native speakers requires sociolinguistic forces so strong so as to override many trends of what has been established as regular linguistic development. This implies that in investigating such cases we might need a modified research methodology and an extended terminology.

Phonological Development and Phonological Processes in the Speech of an English-Arabic Bilin-gual Child

This research traces the phonological development and the phonological processes in the speech of a bilingual child acquiring Jordanian Arabic and English. This trace is carried out through a thorough description of the phonological development of segments in Jordanian Arabic and English. It is also carried out through discussing the phonological processes resorted to by the child in order to simplify the production of segments in both languages. This study is the first of its kind to compare and contrast phonological processes in the speech of a bilingual child whose two first languages descend from two different linguistic families. The study also scrutinizes evidence of any influence of one language over the other. Evidence for either the Separate Development Hypothesis or the Fusion Hypothesis is also investigated. The data used in this paper are collected by the author from her own child acquiring Arabic and English simultaneously between the ages of 7 and 20 months. The child’s sound segment development showed consistency with universal trends. Phonological processes such as regressive and progressive assimilation, substitution and metathesis were found in the child’s production of English and Arabic sounds. The study provides limited evidence for the occurrence of interlanguage interference. On the other hand, the study provides strong supportive evidence for the Separate Development Hypothesis.

Experimental support for the evolution of symmetric protein architecture from a simple peptide motif

The majority of protein architectures exhibit elements of structural symmetry, and “gene duplication and fusion” is the evolutionary mechanism generally hypothesized to be responsible for their emergence from simple peptide motifs. Despite the central importance of the gene duplication and fusion hypothesis, experimental support for a plausible evolutionary pathway for a specific protein architecture has yet to be effectively demonstrated. To address this question, a unique “top-down symmetric deconstruction” strategy was utilized to successfully identify a simple peptide motif capable of recapitulating, via gene duplication and fusion processes, a symmetric protein architecture (the threefold symmetric β-trefoil fold). The folding properties of intermediary forms in this deconstruction agree precisely with a previously proposed “conserved architecture” model for symmetric protein evolution. Furthermore, a route through foldable sequence-space between the simple peptide motif and extant protein fold is demonstrated. These results provide compelling experimental support for a plausible evolutionary pathway of symmetric protein architecture via gene duplication and fusion processes.