DNA sequencing
Next-generation sequencing has become a cornerstone of precision oncology.
This sequencing method detects differences in specific DNA sequences between a sample and a reference genome or matched normal DNA.
NGS detects differences in a patient’s genome from a reference or normal genome.
It allows for the sequencing of multiple genes simultaneously, referred to as multigene testing.
Multigene testing is most useful when more than one gene explains an inherited cancer syndrome.
It identifies sections of DNA that represent variants. including insertions or deletions in a specific DNA sequence or array of sequences.
NGS commonly identifies alterations: base pairs substitutions, including single nucleotide variants; insertions and deletions, typically up to 70 base pairs,; copy number gains and losses including amplifications and deletions,; translocations and rearrangements including inter chromosomal or intra-chromosomal rearrangements.
The genome and transcriptome of tumors or individual cells can be profiled, allowing for the study of specific oncogenic pathways.
DNA sequencing refers to the process of determining the nucleic acid sequence, the order of nucleotides in DNA.
A technique to analyze targeted DNA locations, the whole exome, or the whole genome in a single test.
Single-nucleotide variants, other insertions, deletions, copy number changes, and fusions may be drivers of cancer growth, and represent treatment schemes.
Designed to identify clinically targetable mutations.
NGS testing should be done a diagnosis for all patients with G.I. cancers-BRAC, HER2.
Targeted essays can identify point mutations, small insertions and deletions, fusions/translocations, copy number variations, tumor mutation burden and microsatellite instability.
The results can serve as a predictive and prognostic cancer biomarker.
NGS identifies alterations that can make a difference in diagnosis, especially in some malignancies such as brain tumors, and add to information about prognosis and deciding whether a tumor is primary or metastatic.
It allows a more comprehensive understanding of cellular behavior in various tumor types.
The sequencing process uses various platforms: DNA sequencing, RNA sequencing, single-cell RNA and DNA sequencing, and liquid biopsy.
Obtaining DNA in a minimally invasive fashion from blood samples, either from plasma-also known as cell-free DNA, or from circulating tumor cells.
This testing has been named a “liquid biopsy.”
It is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine.
It can compare healthy and mutated DNA sequences can diagnose diseases including various cancers,and can characterize antibody content and can guide patient treatment.
Following the development of fluorescence-based sequencing methods with a DNA sequencer,[6] DNA sequencing has become easier and orders of magnitude faster.
DNA sequencing may be used to determine the sequence of individual genes, larger genetic regions, such as clusters of genes or operons, full chromosomes, or entire genomes.
It is the most efficient way to indirectly sequence RNA or proteins.
It is used to study genomes and the proteins they encode.
It is used to identify changes in genes, associations with diseases and their phenotypes.
Approximately 300-600 genes known to cause cancer.
Among the thousands of mutations acquired by a cancer cell, evidence suggests only a handful actually instruct the cell to function as an autonomous clone, and these are called driver mutations.
The remaining mutations are named passenger mutations, acquired by the clone before the first drive mutations arose during or after its subsequent transformation.
Driveway mutations include substitutions of one base of DNA for another, insertions, deletions of small numbers of DNA bases, gains and losses of large chromosomal regions or even whole chromosomes, and rearrangements that fuse one gene to another or juxtapose one gene with the regulatory apparatus of a nerve.
It is used to identify potential drug targets.
DNA sequencing may be used along with DNA profiling methods for forensic identification, and paternity testing.
The DNA patterns in fingerprint, saliva, hair follicles, can separate each living organism from another, and detect specific genomes in a DNA strand to produce a unique and individualized pattern.
The structure of DNA has four bases: thymine (T), adenine (A), cytosine (C), and guanine (G).
DNA sequencing refers to then determination of the physical order of these bases in a molecule of DNA.
DNA is composed of two strands of nucleotides coiled around each other, linked together by hydrogen bonds and running in opposite directions.
Each strand is composed of four complementary nucleotides – adenine (A), cytosine (C), guanine (G) and thymine (T) – with an A on one strand always paired with T on the other, and C always paired with G.
Each strand to be used to reconstruct the other, an idea central to the passing on of hereditary information between generations.
Next-generation or second-generation sequencing (NGS) methods, distinguish them from the earlier methods.
NGS technology is typically characterized by being highly scalable, allowing the entire genome to be sequenced at once.
Allows for early detection and more precise investigation of communicable disease outbreaks.
It can categorize microbes more effectively and with his insight into their ecology and transmission.
Initial precision medicine tidies have focused on DNA based technologies.
DNA is transcribed into RNA, and before being translated into protein, it is spliced in messenger RNA, and the pathogenicity of a variant can stem from impact to mRNA splicing.
The paired germline, DNA and RNA sequencing allows greater opportunity for identification of individuals with germline cancer predisposition.