Description

Several recent studies have attempted to approach the idea of genome organization from a more facile standpoint, using only the most basic components of the environment in which genetic material is contained to build models, rather than dealing with complexities that arose through evolution. Toward this end, a nucleus or a prokaryotic cell can be thought of as an environment with DNA (a polymer), DNA binding proteins and non-DNA binding proteins, all confined within a boundary.

Monte Carlo simulations yielding probability distributions for the range of possible outcomes to a problem are a useful computational tool to model genome organization. For simplicity, simulations were first performed to study only DNA-DNA interactions, considering two kinds of polymers in a confined space – flexible ones representing euchromatin and stiff ones representing heterochromatin. Remarkably, simulations showed that spontaneous movement of euchromatin to the interior and heterochromatin to the periphery had the greatest likelihood, recapitulating what is seen in cells. Additionally, stiff polymers exhibited greater contact frequencies, resulting in separation between rigid and flexible polymers. With the knowledge that heterochromatin is transcriptionally inactive and euchromatin is active, this separation resembles the idea that the genome is split into A (active) and B (inactive) compartments. It is important to note that within the confines of these simulations, merely entropic forces act on the genome.

Further, an additional layer of complexity was added to the system in the form of chromatin binding proteins, the system now involving DNA-DNA and DNA-protein interactions. This showed spontaneous aggregation of binding sites as a result of DNA-protein interactions. This promoted further binding of proteins from the soluble pool, in turn increasing local chromatin concentration. It is not hard to imagine then, that if the bound factors have bi- or multi-valency they can effectively bridge out forming chromatin loops that will remain stable for as long as the factors are bound. Such bound clusters and the resultant looping are stabilized again by a non-specific force called depletion attraction, which is in play in crowded environments like cells.

In cells, there are many different transcription factors, each binding to DNA in a sequence specific manner. In such a situation, there would be specialized clusters, effectively separated in 3D space. Specificity can also be conferred by epigenetic marks separating euchromatin from heterochromatin. Thus, each individual transcriptional event would contribute its part in affecting global genome organization. This model of self-assembly and clustering is popularly referred to as the “transcriptional factor model” of genome organization.

In silico models collectively demonstrate how a certain degree of order is achieved in the system merely through entropic forces and stabilized by genome-wide transcriptional events.

Insects, Fish, birds and reptiles 

The process of evolution is crucial to study and understand the evolution mechanism. To understand this evolutionary process, biologists and paleontologists started to explore the anatomical structure and morphological processes of each species. The most prominent species we need to study are insects, fish, reptiles, and birds. Insects are different fish, reptiles, and birds as it is a class of phylum Arthropod.  However,  before  going  into  details  in  those  species,  we  need  to  understand  the morphology  and anatomy of  the chordates.  We  also  need  to  relate  these characteristics to  fish, reptiles and birds. It will help us to understand the evolutionary processes that are associated with the morphological processes and anatomical changes of each species.

The insect is a class under phylum Arthropod. Its body is hard, segmented, and covered by a hard cuticle.  It  is  also  an  exoskeleton contains chitin and protein layers.  Many  of  the  segments have appendages to allow the insect to move, handling food, and reproduce. The body includes the head, thorax,  and abdomen.  The sensory  organs  are  developed  in  insects.  They have  many  sensory organs such as organs of sight, balance, touch, smell, and hearing. Insects have two types of eyes; compound and simple. The brain is developed in insects. It has two or three ganglia that are connected to many ventral nerve ganglia. The essential features of insects that they have two pairs of wings, six legs, and two antennae.

Journal of Entomology, Ornithology & Herpetology: Current Research announces papers for the upcoming issue. Interested can submit their manuscript through online portal.

Submit manuscript at https://www.longdom.org/submissions/entomology-ornithology-herpetology-current-research.html or send as an e-mail attachment to the Editorial Office at herpetolcurrres@longdomjournal.org

Media contact:

Elsa

Managing Editor

Journal of Entomology, Ornithology & Herpetology: Current Research

Mail ID: herpetolcurrres@longdomjournal.org

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