Advances in Genetics

With the availability of DNA-based molecular markers during early 1980s and that of sophisticated statistical tools in late 1980s and later, it became possible to identify genomic regions that control a quantitative trait. The two methods used for this purpose included quantitative trait loci (QTL) interval mapping and genome-wide association mapping/studies (GWAS). Both these methods have their own merits and demerits, so that newer approaches were developed in order to deal with the demerits. We have now entered a post-GWAS era, where either the original data on individual genotypes are being used again keeping in view the results of GWAS or else summary statistics obtained through GWAS is subjected to further analysis...

The commercial production of high quality natural rubber (NR) solely depends on Hevea brasiliensis Muell. Arg, (Para rubber tree) and accounts for >98% of total production worldwide. NR with its unique properties is an essential commodity for the automobile industry and its synthetic counterparts are in no way substitute to it. The rubber tree genome is very complex and plays an important role in delivering the unique properties of Hevea. But a lack of knowledge on the molecular mechanisms of rubber biosynthesis, disease resistance, etc...

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Tuberous sclerosis complex (TSC) is a rare, autosomal dominant genetic condition caused by a mutation in either the TSC1 or TSC2 gene. Phenotypically, this leads to aberrant cell growth and the formation of benign tumors called hamartomas in multiple organs. Understanding the mechanisms of pathology that are caused through the presence of disease causing mutations is a real hurdle for many rare genetic disorders; a limiting factor that restricts knowledge of the disease and any hope of a future cure. Through the discovery of the TSC1 and TSC2 genes and the signaling pathways responsible for the pathology of TSC, a new drug target called mechanistic target of rapamycin complex 1 (mTORC1) was discovered...

Pre-mRNA splicing, an essential step in eukaryotic gene expression, relies on recognition of short sequences on the primary transcript intron ends and takes place along transcription by RNA polymerase II. Exonic and intronic auxiliary elements may modify the strength of exon definition and intron recognition. Splicing DNA variants (SV) have been associated with human genetic diseases at canonical intron sites, as well as exonic substitutions putatively classified as nonsense, missense or synonymous variants...

Colorectal carcinoma (CRC) is the third most common cancer in men and the second most common cancer in women across the world. Most CRCs occur sporadically, but in 15-35% of cases, hereditary factors are important. Some patients with an inherited predisposition to CRC will be diagnosed with a "genetic polyposis syndrome" such as familial adenomatous polyposis (FAP), MUTYH-associated polyposis (MAP), polymerase proofreading associated polyposis (PPAP), NTHL1-associated polyposis, MSH3-associated polyposis or a hamartomatous polyposis syndrome...

Mutations in CDK13 have recently been identified as a novel cause of syndromic intellectual disability. In this chapter, we review the 44 cases of CDK13-related disorder reported to date, highlighting key clinical pointers to this diagnosis including characteristic craniofacial features, feeding difficulties in infancy, and the presence of structural heart or brain malformations. The spectrum of reported mutations is also described, demonstrating an excess of missense mutations arising in the protein kinase domain...

The current excitement for affordable genomics technologies and national precision medicine initiatives marks a turning point in worldwide healthcare practices. The last decade of global population sequencing efforts has defined the enormous extent of genetic variation in the human population resulting in insights into differential disease burden and response to therapy within and between populations. Population-scale pharmacogenomics helps to provide insights into the choice of optimal therapies and an opportunity to estimate, predict and minimize adverse events...

For several decades, researchers are working toward improving the "major" crops for better adaptability and tolerance to environmental stresses. However, little or no research attention is given toward neglected and underutilized crop species (NUCS) which hold the potential to ensure food and nutritional security among the ever-growing global population. NUCS are predominantly climate resilient, but their yield and quality are compromised due to selective breeding. In this context, the importance of omics technologies namely genomics, transcriptomics, proteomics, phenomics and ionomics in delineating the complex molecular machinery governing growth, development and stress responses of NUCS is underlined...

Darwin clearly described certain anomalous phenomena, including what he referred to as "the direct action of the male element on the female form" and what we now call xenia and telegony, bud variation (mutation), reversion or atavism, and the inheritance and non-inheritance of mutilation. Some phenomena, particularly xenia, telegony and the inheritance of mutilation, were considered as doubtful phenomena by such authorities as Weismann and Morgan. Over the past 150 year, however, there has been increasing evidence for xenia, which is of great interest and importance in physiological research and plant production...

Darwin had many close connections with medical men, and made a number of observations on inherited diseases, clearly describing the inheritance of sex-linked diseases, inherited diseases at corresponding ages, infectious disease and the causes of diseases. Darwin's Pangenesis provides an alternative explanation for cancer metastasis, and is now supported by the discovery of circulating tumour DNA. The "genometastasis hypothesis" proposed by Garcia-Olmo et al. is consistent with Pangenesis. Darwin's view of animal regeneration and his pangenetic explanation is also supported by the recent finding regarding the role of small RNAs and extracellular vesicles in regeneration...

Although there were many records of graft-induced variations in ancient China, it was Darwin who coined the term "graft hybridization", the formation of hybrids between distinct species or varieties, through plant grafting, without the intervention of the sexual organs. He described many cases of the so-called "graft hybrids", in which shoots produced from grafted plants exhibited a combination of characters of both rootstock and scion, and explained their formation by his Pangenesis. Michurin invented "mentor-grafting" and "preliminary vegetative approximation" methods, which greatly increased the production of graft hybrids, thus providing a solution to Darwin's puzzle...

Since the end of the 19th century, Lamarck's name has been tightly linked to the notion of the inheritance of acquired characters. Darwin regarded Lamarck as a great zoologist and a forerunner of evolution, and repeatedly expressed the opinion that "natural selection has been the main but not the exclusive means of modification." The original Darwinism not only includes natural selection, but also the inheritance of acquired characters and mutation. Neo-Darwinism considers natural selection as the one controlling process of evolution, but denies the inheritance of acquired characters...

Darwin carried out a host of carefully controlled cross- and self-pollination experiments in a wide variety of plants, and made a significant and imperishable contribution to the knowledge of hybridization. He not only clearly described the phenomenon of what he called prepotency and what we now call dominance or Mendelian inheritance, but also explained it by his Pangenesis. Recent discovery of small RNAs acting as dominance modifiers supports his Pangenesis regarding the control of prepotency by gemmules...

Darwin's gemmules were supposed to be "thrown off" by cells and were "inconceivably minute and numerous as the stars in heaven." They were capable of self-propagation and diffusion from cell to cell, and circulation through the system. The word "gene" coined by Wilhelm Johannsen, was derived from de Vries's term "pangen," itself a substitute for "gemmule" in Darwin's Pangenesis. Johannsen resisted the "morphological" conception of genes as particles with a certain structure...

Although Darwin's Pangenesis received strong criticism and never gained any very wide acceptance, it was of great importance due to its stimulating effect on later work and thought. Nearly every major theory of heredity developed in the late 19th century began with a discussion of Darwin's Pangenesis. Darwin was shown to play a more important role in the history of genetics than hitherto attributed to him by historians through a detailed analysis of the influence of his Pangenesis on de Vries' "Intracellular Pangenesis" and "The Mutation Theory," Weismann's theory of "Continuity of the Germ-plasm," Galton's "A Theory of Heredity" and "Natural Inheritance," Brooks' "The Law of Heredity, Ross's "Graft Theory of Diseases", Haeckel's perigenesis and Kozo-Polyansky's hypothetical version of symbiogenesis...

When first published in 1868, Darwin's Pangenesis was almost uniformly rejected by his contemporaries. Until recently it has still been regarded as Darwin's biggest mistake or a brilliant blunder. There are three main reasons for this. First, Galton transfused the blood of one variety of rabbit into another, and then bred together the latter. The results of breeding showed no variations of characters in the offspring. Thus he concluded that Darwin's Pangenesis was incorrect. Second, there was no direct evidence for the existence of Darwin's imaginary gemmules...

Since the earliest days of evolutionary thought, the problem of the inheritance of acquired characters has been a central debate. Darwin accepted the inheritance of acquired characters as an established fact and gave many instances. His Pangenesis was more than anything else an attempt to provide a theory for its explanation. Over the past several decades, there has been increasing evidence for the inheritance of acquired habit and immunity, and for heritable changes induced by food and fertilizer, stress, chemicals, temperature, light and other environmental factors...

This chapter briefly discusses Darwin's The Origin of Species and its companion volume The Variation of Animals and Plants under Domestication. It is in the second great book that Darwin took a broad survey of the whole range of variation and heredity, and developed his Pangenesis, an expanded cell theory and a unified genetical theory that would strengthen his theory of evolution and explains the numerous phenomena of life. The essential assumption of Pangenesis is the existence of inherited particles or molecules called gemmules, and their production by cells at each stage of development...

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