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Cancer: A Genetic Disease
Published in Jeremy R. Jass, Understanding Pathology, 2020
To demonstrate linkage one needs to ‘follow’ genetic material through successive family generations. Such gene tracking is achieved with genetic markers that allow maternal and paternal DNA to be distinguished (since eye colour cannot be used in practice). Much of the DNA in chromosomes has no known function. Unlike junk mail, however, this DNA can be put to good use by the geneticist. Because it is junk, the non-coding DNA may accumulate mutations that are harmless. This accumulation leads to genetic variation (polymorphism) between individuals. And within one individual there will be variation between the maternal and paternal junk mail. How can this variation be detected? The tracking of linked genetic loci changed from wishful thinking to reality with the development of recombinant DNA technology, specifically Southern blotting and polymerase chain reaction based methods. Southern blotting will be considered first as it was the technique that resulted in the initial breakthroughs.
Awesome analysis
Published in Brendan Curran, A Terrible Beauty is Born, 2020
Genome is the word used to denote all of the DNA sequences that an organism possesses. As creatures became more complex, they required more genes to encode the proteins for their structures, maintenance and reproduction. Multi-cellular organisms (the plants and animals we see all about us), not surprisingly, possess genomes substantially larger and significantly more complex than those of single-celled species like bacteria or yeast. The simple nematode worm, with a body containing fewer than 1,000 cells, requires 19,099 genes in order to function, whereas the assembly of a human body with 50 trillion cells needs an additional 55,000 genes which are not found in the simpler nematode. Complex genomes also contain large chunks of genetic material with no apparent role for encoding cellular proteins. This non-coding DNA, often called junk, may act as a reservoir from which new genes with novel functions can emerge, although nobody really knows for sure why it is there; it is so prevalent in higher organisms that only 90 million of the 3 billion bases in the human genome actually encode proteins! About 97% of our DNA is junk.
Clinical Cytogenetics and Testing for Developmental Disabilities
Published in Merlin G. Butler, F. John Meaney, Genetics of Developmental Disabilities, 2019
Joan H. M. Knoll, Linda D. Cooley
Marker chromosomes are chromosomes whose origin cannot be recognized by their GTG-banding pattern and are sometimes referred to as ESACs. These chromosomes are generally small and have a centromere. Their effect on the phenotype is dependent upon their genetic composition. In the initial laboratory work-up to identify the chromosomal origin or composition of a marker chromosome, C-banding and NOR staining are generally performed to determine if the marker is comprised of heterochromatin and/or active ribosomal genes (or satellites or NORs) from the acrocentric chromosomes, respectively. Markers that are comprised only of heterochromatin, repetitive noncoding DNA, or active ribosomal genes are without phenotypic effect. However, those containing euchromatin often have an adverse effect on the phenotype (35). Fluorescence in situ hybridization is useful in identifying the chromosomal origin of the marker chromosome (36,37) and, in some instances, determining the precise source of the marker chromosome.
Ghrelin intronic lncRNAs, lnc-GHRL-3:2 and lnc-GHRL-3:3, as novel biomarkers in type 2 diabetes mellitus
Published in Archives of Physiology and Biochemistry, 2023
Dalia M. Anbari, Rowyda N. Al-Harithy
Of the total human genome, less than 2% of the total DNA sequence is made up of protein- coding genes and at least 90% of the genome is actively transcribed as non-coding genes (Pertea 2012). The vast majority of the non-coding DNA contains many types of regulatory elements including long non-coding RNAs (lncRNAs) (Rinn and Chang 2012). The lncRNAs are transcripts of sizes longer than 200 nucleotides in length and may have their own promoters (Barra and Leucci 2017). Although lncRNAs have no protein-coding ability, they may have short open reading frames (ORFs). They also participate in transcriptional level regulation, as well as in mRNA processing at the post-transcriptional level, and in regulating alternative splicing (Barra and Leucci 2017). The functions of lncRNAs are extremely complex as they do not function in a single manner or independently but instead, they interact with other genes and proteins (Barra and Leucci 2017, Fernandes et al. 2019). Lately, a large number of lncRNAs have been identified, with increasing evidence that demonstrate their important roles in various biological processes (Fang and Fullwood 2016, Sun et al. 2017). Furthermore, the dysfunctions of lncRNAs were found to be associated with a range of diseases (Barra and Leucci 2017, Fernandes et al. 2019).
Heterochromatin extension: a possible cytogenetic fate of primary amenorrhea along with normal karyotype
Published in Journal of Obstetrics and Gynaecology, 2022
Bishal Kumar Dey, Shanoli Ghosh, Ajanta Halder, Somajita Chakraborty, Sanchita Roy
The region of heterochromatin also acts as a key part in chromosome structure, histone modification and gene regulation. There is evidence from where we come to know that there may be displacement of heterochromatin from one chromosome to another. Perhaps, this displacement is helping in the extension of a particular chromosome at the heterochromatin portion of the long arm (Bannister and Kouzarides 2011). The mechanisms of spindle fibres, chromosome movement, meiosis crossover and change of sister chromatids are considered to be the integral region as heterochromatin for a chromosome. At the time of meiosis, there may be a change in area of synapses of homologous chromosomes in the polymorphic heterochromatin region. The heterochromatin in chromosomal polymorphism can also regulate gene expression by reversible transformation between heterochromatin (non-coding DNA sequences) and euchromatin (expressed DNA sequences) thus justifying certain clinical expression like short stature or PA. It was also postulated that defective histone protein methylation due to presence of heteromorphic variants may play a more crucial role in ovarian failure. Association of heterochromatin polymorphism with ovarian dysgenesis may be a reason for the occurrence of PA. For that, we need to study on a greater number of patients on the basis of their nucleosome’s functionality and heteromorphic polymorphism by sequencing.
Novel therapeutic targets for cancer metastasis
Published in Expert Review of Anticancer Therapy, 2020
Konstantin Stoletov, Perrin H. Beatty, John D. Lewis
Recently, large-scale sequencing projects that analyzed up to 1013 prostate cancer cell lines have been published that have identified novel coding and noncoding genetic drivers of cancer cell initiation and metastatic progression [17,34,35]. For decades genetic biologists primarily described metastasis according to which protein gene products were differentially expressed during metastatic disease. However, with the recent understanding that the majority (75%) of the human genome is comprised of noncoding RNAs such as microRNA (miRNA), short interfering RNA (siRNA) and long noncoding RNA (lncRNA), while protein encoding genes make up only 3% of the human genome, biologists have increasingly become interested in the noncoding DNA function [35,36]. With the advent of new molecular tools and visualization methods comes the discovery that many noncoding RNAs are functionally important in metastatic cancers [36]. For example, metastatic breast cancer cells regulate migration through surrounding tissue by secretion of miR-105. This noncoding miRNA mediates the destruction of the intercellular tight junctions that are natural barriers to metastasis by targeting the tight junction protein ZO-1 [33]. In addition, when non-metastatic cancer cells overexpress miR-105 they become metastatic [33].