Repetitive sequence and sex chromosome evolution in vertebrates

Sex chromosomes are the most dynamic entity in any genome having unique morphology, gene content, and evolution. They have evolved multiple times and independently throughout vertebrate evolution. One of the major genomic changes that pertain to sex chromosomes involves the amplification of common repeats. It is hypothesized that such amplification of repeats facilitates the suppression of recombination, leading to the evolution of heteromorphic sex chromosomes through genetic degradation of Y or W chromosomes. Although contrasting evidence is available, it is clear that amplification of simple repetitive sequences played a major role in the evolution of Y and W chromosomes in vertebrates. In this review, we present a brief overview of the repetitive DNA classes that accumulated during sex chromosome evolution, mainly focusing on vertebrates, and discuss their possible role and potential function in this process.</jats:p

Tracing the evolution of amniote chromosomes

A great deal of diversity in chromosome number and arrangement is observed across the amniote phylogeny. Understanding how this diversity is generated is important for determining the role of chromosomal rearrangements in generating phenotypic variation and speciation. Gaining this understanding is achieved by reconstructing the ancestral genome arrangement based on comparisons of genome organization of extant species. Ancestral karyotypes for several amniote lineages have been reconstructed, mainly from cross-species chromosome painting data. The availability of anchored whole genome sequences for amniote species has increased the evolutionary depth and confidence of ancestral reconstructions from those made solely from chromosome painting data. Nonetheless, there are still several key lineages where the appropriate data required for ancestral reconstructions is lacking. This review highlights the progress that has been made towards understanding the chromosomal changes that have occurred during amniote evolution and the reconstruction of ancestral karyotypes

Time course nutrient uptake study of some intertidal rocky shore macroalgae and the limiting effect due to synergistic interaction

287-292The time course nutrient uptake study of some intertidal rocky shore macroalgae showed a marked variation in the uptake of nutrients. In the present study, Caulerpa sertularioides, Padina tetrastomatica, Sargassum cinctum, andGracilaria corticata which are slow growingassimilated ammonium, whereas the fast growing Chaetomorpha antennina, Ulva flexuosa, and Ulva lactuca assimilated nitrate. Nitrate in the medium was assimilated quickly by these three species. It was below the detection level after five hours. The study showed that the characteristic of nutrient uptake varies between different macroalgae. The slow growing perennial macroalgae preferred ammonium and fast growing annuals preferred nitrate.The preference of different form of nitrogen is inferred to be mainly due to low energetic cost and opportunistic uptake. The combination of nutrient-N and phosphate in the medium showed a synergistic interactive effect in some of the algae wherein the uptake of nutrient was slowed comparatively. This synergistic interactive effect was significant (P Caulerpa sertularioides, Chaetomorpha antennina,and Ulva lactuca

A Measurement of Customer Service Quality of Banks in Dhaka City of Bangladesh

Volume 12, No. 1, January-March, pp. 37-5

Sex-linked markers in the North American green frog (Rana clamitans) developed using DArTseq provide early insight into sex chromosome evolution

BACKGROUND: The extent to which sex reversal is associated with transitions in sex determining systems (XX-XY, ZZ-ZW, etc.) or abnormal sexual differentiation is predominantly unexplored in amphibians. This is in large part because most amphibian taxa have homomorphic sex chromosomes, which has traditionally made it challenging to identify discordance between phenotypic and genetic sex in amphibians, despite all amphibians having a genetic component to sex determination. Recent advances in molecular techniques such as genome complexity reduction and high throughput sequencing present a valuable avenue for furthering our understanding of sex determination in amphibians and other taxa with homomorphic sex chromosomes like many fish and reptiles. RESULTS: We use DArTseq as a novel approach to identify sex-linked markers in the North American green frog (Rana clamitans melanota) using lab-reared tadpoles as well as wild-caught adults from seven ponds either in undeveloped, forested habitats or suburban ponds known to be subject to contamination by anthropogenic chemicals. The DArTseq methodology identified 13 sex-linked SNP loci and eight presence-absence loci associated with males, indicating an XX-XY system. Both alleles from a single locus show partial high sequence homology to Dmrt1, a gene linked to sex determination and differentiation throughout Metazoa. Two other loci have sequence similarities to regions of the chimpanzee and human X-chromosome as well as the chicken Z-chromosome. Several loci also show geographic variation in sex-linkage, possibly indicating sex chromosome recombination. While all loci are statistically sex-linked, they show varying degrees of female heterozygosity and male homozygosity, providing further evidence that some markers are on regions of the sex chromosomes undergoing higher rates of recombination and therefore further apart from the putative sex determining locus. CONCLUSION: The ease of the DArTseq platform provides a useful avenue for future research on sex reversal and sex chromosome evolution in vertebrates, particularly for non-model species with homomorphic or cryptic or nascent sex chromosomes. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12864-016-3209-x) contains supplementary material, which is available to authorized users

Performance Analysis Vapour Absorption Refrigeration Chiller Run by Solar Thermal Energy

Over the past few decades, energy is the backbone of technology and economic development. In addition to men, machines and money, ‘energy' is now the fourth factor of production. The objective of this paper is to design and study an environment friendly ammonia water vapour absorption refrigeration system of unit capacity using Ammonia (R717) as a refrigerant and water as a absorbent working fluids and run by exhaust water Solar Thermal Set Up. The system is designed and tested in Thermal Engineering lab of Agnos College of technology RKDF University Bhopal Madhya Pradesh for various operating conditions using hot water as heat source. In this paper, performance of the fabricated system is outlined with respect to various operating conditions related to heat source, condenser, absorber and evaporator temperatures. The solar heating unit remains idle in the summer months. Also the solar potential is at maximum in the summer other months of year

Relationships between vertebrate ZW and XY Sex Chromosome Systems

The peculiar cytology and unique evolution of sex chromosomes raise many fundamental questions. Why and how sex chromosomes evolved has been debated over a century since H.J. Muller suggested that sex chromosome pairs evolved ultimately from a pair of autosomes. This theory was adapted to explain variations in the snake ZW chromosome pair and later the mammal XY. S. Ohno pointed out similarities between the mammal X and the bird/reptile Z chromosomes forty years ago, but his speculation that they had a common evolutionary origin, or at least evolved from similar regions of the genome, has been undermined by comparative gene mapping, and it is accepted that mammal XY and reptile ZW systems evolved independently from a common ancestor. Here we review evidence for the alternative theory, that ZW⇔XY transitions occurred during evolution, citing examples from fish and amphibians, and probably reptiles. We discuss new work from comparative genomics and cytogenetics that leads to a reconsideration of Ohno's idea and advance a new hypothesis that the mammal XY system may have arisen directly from an ancient reptile ZW system

A Review on The Thermal Analysis of Air Flow Gap

More than half of all electrical energy is consumed by motors and generators in an industrialized country. This energy is lost and converted to heat. This heat produced by the losses has adverse effect on the lifetime and performance of a machine. A machine has to be operated at a given temperature to achieve maximum efficiency, therefore heat transfer study of machines is of special interest to rotating machines manufacturers. In this paper we can investigate the heat transfer in the air-gap between the rotor and the stator of a simplified induction motor using Computational Fluid Dynamics. We can consider different air-gap widths and rotation speeds to explore the change in air-gap heat transfer when changing the air-gap width and the rotation speed

Transnationalism and place attachment: sustainable campus planning towards the establishment of global educational hub

Malaysia fundamentally needs to understand the adjustment problems faced by increasing international students’ enrollments in its inspiration to become a premier international education hub. This can be facilitated with the right kind of support by enhancing sense of place attachment amongst the transnationals. The physical planning of Universiti Putra Malaysia (UPM) main campus is outspread due to its large area and seems to contribute to the lack of social interactions and attachment to the university that can assist in improving their campus lifestyles. The aim of this study is investigate the international students’ perception of current place attachment in UPM. A5-points Likert-scaled questionnaire survey on 146 UPM international students and data analysis using SPSS were conducted. Results demonstrate that the tangible physical planning of UPM campus influenced international students’ level of place attachment towards the campus surroundings and their positive lifestyles. However, more improvements to the current planning to enhance social interactions, safety and human comfort are needed to enhance the place attachments in the planning process

Restriction Site-Associated DNA Sequencing (RAD-seq) Reveals an Extraordinary Number of Transitions among Gecko Sex-Determining Systems

Sex chromosomes have evolved many times in animals and studying these replicate evolutionary “experiments” can help broaden our understanding of the general forces driving the origin and evolution of sex chromosomes. However this plan of study has been hindered by the inability to identify the sex chromosome systems in the large number of species with cryptic, homomorphic sex chromosomes. Restriction site-associated DNA sequencing (RAD-seq) is a critical enabling technology that can identify the sex chromosome systems in many species where traditional cytogenetic methods have failed. Using newly generated RAD-seq data from 12 gecko species, along with data from the literature, we reinterpret the evolution of sex-determining systems in lizards and snakes and test the hypothesis that sex chromosomes can routinely act as evolutionary traps. We uncovered between 17 and 25 transitions among gecko sex-determining systems. This is approximately one-half to two-thirds of the total number of transitions observed among all lizards and snakes. We find support for the hypothesis that sex chromosome systems can readily become trap-like and show that adding even a small number of species from understudied clades can greatly enhance hypothesis testing in a model-based phylogenetic framework. RAD-seq will undoubtedly prove useful in evaluating other species for male or female heterogamety, particularly the majority of fish, amphibian, and reptile species that lack visibly heteromorphic sex chromosomes, and will significantly accelerate the pace of biological discovery