Molecular biology is the branch of biology that concerns the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms and interactions. The central dogma of molecular biology describes the process in which DNA is transcribed into RNA, then translated into protein.
Polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it to a large enough amount to study in detail. PCR was invented in 1983 by the American biochemist Kary Mullis at Cetus Corporation. It is fundamental to much of genetic testing including analysis of ancient samples of DNA and identification of infectious agents. Using PCR, copies of very small amounts of DNA sequences are exponentially amplified in a series of cycles of temperature changes. PCR is now a common and often indispensable technique used in medical laboratory research for a broad variety of applications including biomedical research and criminal forensics.
A primer is a short single-stranded nucleic acid utilized by all living organisms in the initiation of DNA synthesis. The enzymes responsible for DNA replication, DNA polymerases, are only capable of adding nucleotides to the 3’-end of an existing nucleic acid, requiring a primer be bound to the template before DNA polymerase can begin a complementary strand. Living organisms use solely RNA primers, while laboratory techniques in biochemistry and molecular biology that require in vitro DNA synthesis usually use DNA primers, since they are more temperature stable.
Reverse transcription polymerase chain reaction (RT-PCR) is a laboratory technique combining reverse transcription of RNA into DNA and amplification of specific DNA targets using polymerase chain reaction (PCR). It is primarily used to measure the amount of a specific RNA. This is achieved by monitoring the amplification reaction using fluorescence, a technique called real-time PCR or quantitative PCR (qPCR). Combined RT-PCR and qPCR are routinely used for analysis of gene expression and quantification of viral RNA in research and clinical settings.
In molecular biology, an amplicon is a piece of DNA or RNA that is the source and/or product of amplification or replication events. It can be formed artificially, using various methods including polymerase chain reactions (PCR) or ligase chain reactions (LCR), or naturally through gene duplication. In this context, amplification refers to the production of one or more copies of a genetic fragment or target sequence, specifically the amplicon. As it refers to the product of an amplification reaction, amplicon is used interchangeably with common laboratory terms, such as "PCR product."
Cycling probe technology (CPT) is a molecular biological technique for detecting specific DNA sequences. CPT operates under isothermal conditions. In some applications, CPT offers an alternative to PCR. However, unlike PCR, CPT does not generate multiple copies of the target DNA itself, and the amplification of the signal is linear, in contrast to the exponential amplification of the target DNA in PCR. CPT uses a sequence specific chimeric probe which hybridizes to a complementary target DNA sequence and becomes a substrate for RNase H. Cleavage occurs at the RNA internucleotide linkages and results in dissociation of the probe from the target, thereby making it available for the next probe molecule. Integrated electrokinetic systems have been developed for use in CPT.
A real-time polymerase chain reaction, also known as quantitative Polymerase Chain Reaction (qPCR), is a laboratory technique of molecular biology based on the polymerase chain reaction (PCR). It monitors the amplification of a targeted DNA molecule during the PCR, not at its end, as in conventional PCR. Real-time PCR can be used quantitatively and semi-quantitatively.
A transgene is a gene that has been transferred naturally, or by any of a number of genetic engineering techniques from one organism to another. The introduction of a transgene, in a process known as transgenesis, has the potential to change the phenotype of an organism. Transgene describes a segment of DNA containing a gene sequence that has been isolated from one organism and is introduced into a different organism. This non-native segment of DNA may either retain the ability to produce RNA or protein in the transgenic organism or alter the normal function of the transgenic organism's genetic code. In general, the DNA is incorporated into the organism's germ line. For example, in higher vertebrates this can be accomplished by injecting the foreign DNA into the nucleus of a fertilized ovum. This technique is routinely used to introduce human disease genes or other genes of interest into strains of laboratory mice to study the function or pathology involved with that particular gene.
This glossary of genetics is a list of definitions of terms and concepts commonly used in the study of genetics and related disciplines in biology, including molecular biology and evolutionary biology. It is intended as introductory material for novices; for more specific and technical detail, see the article corresponding to each term. For related terms, see Glossary of evolutionary biology.
SNP genotyping is the measurement of genetic variations of single nucleotide polymorphisms (SNPs) between members of a species. It is a form of genotyping, which is the measurement of more general genetic variation. SNPs are one of the most common types of genetic variation. A SNP is a single base pair mutation at a specific locus, usually consisting of two alleles. SNPs are found to be involved in the etiology of many human diseases and are becoming of particular interest in pharmacogenetics. Because SNPs are conserved during evolution, they have been proposed as markers for use in quantitative trait loci (QTL) analysis and in association studies in place of microsatellites. The use of SNPs is being extended in the HapMap project, which aims to provide the minimal set of SNPs needed to genotype the human genome. SNPs can also provide a genetic fingerprint for use in identity testing. The increase of interest in SNPs has been reflected by the furious development of a diverse range of SNP genotyping methods.
An allele-specific oligonucleotide (ASO) is a short piece of synthetic DNA complementary to the sequence of a variable target DNA. It acts as a probe for the presence of the target in a Southern blot assay or, more commonly, in the simpler Dot blot assay. It is a common tool used in genetic testing, forensics, and Molecular Biology research.
Loop-mediated isothermal amplification (LAMP) is a single-tube technique for the amplification of DNA and a low-cost alternative to detect certain diseases. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) combines LAMP with a reverse transcription step to allow the detection of RNA.
A nucleic acid test (NAT) is a technique used to detect a particular nucleic acid sequence and thus usually to detect and identify a particular species or subspecies of organism, often a virus or bacteria that acts as a pathogen in blood, tissue, urine, etc. NATs differ from other tests in that they detect genetic materials rather than antigens or antibodies. Detection of genetic materials allows an early diagnosis of a disease because the detection of antigens and/or antibodies requires time for them to start appearing in the bloodstream. Since the amount of a certain genetic material is usually very small, many NATs include a step that amplifies the genetic material—that is, makes many copies of it. Such NATs are called nucleic acid amplification tests (NAATs). There are several ways of amplification, including polymerase chain reaction (PCR), strand displacement assay (SDA), or transcription mediated assay (TMA).
The versatility of polymerase chain reaction (PCR) has led to a large number of variants of PCR.
MAGIChips, also known as "microarrays of gel-immobilized compounds on a chip" or "three-dimensional DNA microarrays", are devices for molecular hybridization produced by immobilizing oligonucleotides, DNA, enzymes, antibodies, and other compounds on a photopolymerized micromatrix of polyacrylamide gel pads of 100x100x20µm or smaller size. This technology is used for analysis of nucleic acid hybridization, specific binding of DNA, and low-molecular weight compounds with proteins, and protein-protein interactions.
Multiplex polymerase chain reaction refers to the use of polymerase chain reaction to amplify several different DNA sequences simultaneously. This process amplifies DNA in samples using multiple primers and a temperature-mediated DNA polymerase in a thermal cycler. The primer design for all primers pairs has to be optimized so that all primer pairs can work at the same annealing temperature during PCR.
Molecular cloning is a set of experimental methods in molecular biology that are used to assemble recombinant DNA molecules and to direct their replication within host organisms. The use of the word cloning refers to the fact that the method involves the replication of one molecule to produce a population of cells with identical DNA molecules. Molecular cloning generally uses DNA sequences from two different organisms: the species that is the source of the DNA to be cloned, and the species that will serve as the living host for replication of the recombinant DNA. Molecular cloning methods are central to many contemporary areas of modern biology and medicine.
Suspension array technology is a high throughput, large-scale, and multiplexed screening platform used in molecular biology. SAT has been widely applied to genomic and proteomic research, such as single nucleotide polymorphism (SNP) genotyping, genetic disease screening, gene expression profiling, screening drug discovery and clinical diagnosis. SAT uses microsphere beads to prepare arrays. SAT allows for the simultaneous testing of multiple gene variants through the use of these microsphere beads as each type of microsphere bead has a unique identification based on variations in optical properties, most common is fluorescent colour. As each colour and intensity of colour has a unique wavelength, beads can easily be differentiated based on their wavelength intensity. Microspheres are readily suspendable in solution and exhibit favorable kinetics during an assay. Similar to flat microarrays, an appropriate receptor molecule, such as DNA oligonucleotide probes, antibodies, or other proteins, attach themselves to the differently labeled microspheres. This produces thousands of microsphere array elements. Probe-target hybridization is usually detected by optically labeled targets, which determines the relative abundance of each target in the sample.
Genetic engineering can be accomplished using multiple techniques. There are a number of steps that are followed before a genetically modified organism (GMO) is created. Genetic engineers must first choose what gene they wish to insert, modify, or delete. The gene must then be isolated and incorporated, along with other genetic elements, into a suitable vector. This vector is then used to insert the gene into the host genome, creating a transgenic or edited organism. The ability to genetically engineer organisms is built on years of research and discovery on how genes function and how we can manipulate them. Important advances included the discovery of restriction enzymes and DNA ligases and the development of polymerase chain reaction and sequencing.
Molecular diagnostics is a collection of techniques used to analyze biological markers in the genome and proteome—the individual's genetic code and how their cells express their genes as proteins—applying molecular biology to medical testing. The technique is used to diagnose and monitor disease, detect risk, and decide which therapies will work best for individual patients.
