PCR (Polymerase Chain Reaction)

PCR

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 1984 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 and clinical laboratory research for a broad variety of applications including biomedical research and criminal forensics.

The majority of PCR methods rely on thermal cycling. Thermal cycling exposes reactants to repeated cycles of heating and cooling to permit different temperature-dependent reactions – specifically, DNA melting and enzyme-driven DNA replication. PCR employs two main reagents – primers (which are short single strand DNA fragments known as oligonucleotides that are a complementary sequence to the target DNA region) and a DNA polymerase. In the first step of PCR, the two strands of the DNA double helix are physically separated at a high temperature in a process called Nucleic acid denaturation. In the second step, the temperature is lowered and the primers bind to the complementary sequences of DNA. The two DNA strands then become templates for DNA polymerase to enzymatically assemble a new DNA strand from free nucleotides, the building blocks of DNA. As PCR progresses, the DNA generated is itself used as a template for replication, setting in motion a chain reaction in which the original DNA template is exponentially amplified.

Almost all PCR applications employ a heat-stable DNA polymerase, such as Taq polymerase, an enzyme originally isolated from the thermophilic bacterium Thermus aquaticus. If the polymerase used was heat-susceptible, it would denature under the high temperatures of the denaturation step. Before the use of Taq polymerase, DNA polymerase had to be manually added every cycle, which was a tedious and costly process.

Applications of the technique include DNA cloning for sequencing, gene cloning and manipulation, gene mutagenesis; construction of DNA-based phylogenies, or functional analysis of genes; diagnosis and monitoring of hereditary diseases; amplification of ancient DNA; analysis of genetic fingerprints for DNA profiling (for example, in forensic science and parentage testing); and detection of pathogens in nucleic acid tests for the diagnosis of infectious diseases.

CRISPRCas9

CRISPRCas9

CRISPR-Cas9 is a method of genome editing that exploits a natural DNA-snipping enzyme in bacteria, called Cas9 (CRISPR-associated protein 9) to target and edit particular genes. CRISPR stands for Clustered regularly interspaced short palindromic repeats, which are segments of DNA of a particular structure found widely in bacteria and archaea (prokaryotes). In the wild, the CRISPR-Cas9 system is part of the prokaryotic immune system, which can snip out of the genome DNA acquired from foreign sources such as phages (bacterial viruses). The same molecular machinery is now being used to enable genetic material to be cut from and pasted into the genomes of other organisms, including eukaryotes such as humans. It might offer a tool for curing genetically based diseases.

DNA has become a versatile polymeric substrate for making nanotechnological structures and artificial molecular-scale machinery for computation, pattern formation, and nanoscale assembly. For several decades now, these efforts have drawn on methods developed in and for biotechnology, and similarly they are likely to find ways of exploiting the advantages of the new technique called CRISPR/Cas9 for manipulating DNA. #CRISPRCas9

CRISPR-Cas9 is a method of genome editing that exploits a natural DNA-snipping enzyme in bacteria, called Cas9 (CRISPR-associated protein 9) to target and edit particular genes. CRISPR stands for Clustered regularly interspaced short palindromic repeats, which are segments of DNA of a particular structure found widely in bacteria and archaea (prokaryotes). In the wild, the CRISPR-Cas9 system is part of the prokaryotic immune system, which can snip out of the genome DNA acquired from foreign sources such as phages (bacterial viruses). The same molecular machinery is now being used to enable genetic material to be cut from and pasted into the genomes of other organisms, including eukaryotes such as humans. It might offer a tool for curing genetically based diseases.

DNA has become a versatile polymeric substrate for making nanotechnological structures and artificial molecular-scale machinery for computation, pattern formation, and nanoscale assembly. For several decades now, these efforts have drawn on methods developed in and for biotechnology, and similarly they are likely to find ways of exploiting the advantages of the new technique called CRISPR/Cas9 for manipulating DNA.

Antibody (Immunoglobulin)

Antibody:
Antibody also called immunoglobulin, a protective protein produced by the immune system in response to the presence of a foreign substance, called an antigen.
When an alien substance enters the body, the immune system is able to recognize it as foreign because molecules on the surface of the antigen differ from those found in the body.
Antibodies are produced by specialized white blood cells called B lymphocytes (or B cells). When an antigen binds to the B-cell surface, it stimulates the B cell to divide and mature into a group of identical cells called a clone. The mature B cells, called plasma cells, secrete millions of antibodies into the bloodstream and lymphatic system.

Antibody structure:
The four-chain structure of an antibody, or immunoglobulin, molecule. The basic unit is composed of two identical light (L) chains and two identical heavy (H) chains, which are held together by disulfide bonds to form a flexible Y shape. Each chain is composed of a variable (V) region and a constant (C) region.

Antibodies are grouped into five classes according to their constant region.
Each class is designated by a letter attached to an abbreviation of the word immunoglobulin: IgG, IgM, IgA, IgD, and IgE.

CORONAVIRUS

Coronaviruses (CoV) are a large family of viruses that cause illness ranging from the common cold to more severe diseases such as Middle East Respiratory Syndrome (MERS-CoV) and Severe Acure Respiratory Syndrome (SARS-CoV). A novel coronavirus (nCoV) is a new strain that has not been proviously identified in humans.

Coronaviruses are a family of viruses that cause disease in animals. Detailed investigations found that SARS-CoV was transmitted from civet cats to human and MERS-CoV from dromedary camels to humans. Several known coronaviruses are circulating in animals that have not yet infected humans.

The new coronavirus, officially called Covid-19 currently has fatality rate between 0.7 per cent to 3.4 per cent. This is much lower than fatality rates for Mers (30 per cent) and SARS (10 per cent), but still a significant threat. However, the new coronavirus (Covid-19) is spreading fast. The bulk cases and fatalities have been confined to China, but the virus is spreading internationally.

The source of the coronavirus is believed to be a "wet market" in Wuhan which sell both dead and live animals including fish and birds. Such markets pose a heightened risk of viruses, jumping from animals to humans because hygiene standards are difficult to maintain if live animals are being kept and butchered on site. Typically, they are also densely packed.

The animal source of the latest outbreak has not yet been identified, but the original host is thought to be bats. Bats were not sold at the Wuhan market but may have infected live chickens or other animals sold there.

Bats are host to a wide range of zoonotic viruses including Ebola, HIV and rabies.

Scientist in China believe that Covid-19 has mutated into two strains, one more aggressive than the other, which could make developing a vaccine more complicated.

It is impossible to say which way the disease will go but, on its current trajectory, it is likely to spread to more countries, affecting many more people. The number of cases is beginning to decrease in China but is increasing in the rest of the world.

Initial common symptoms of Covid-19 include fever, dry cough, tiredness and a general feeling of being unwell. In more severe cases, infection can cause pneumonia, severe acute respiratory syndrome, kidney failure and even death. Symptoms are thought to appear between 2 and 10 days later after contracting the virus, but it may be up to 24 days

The virus is spread via droplets when a person coughs or sneezes. The droplets land on surfaces and are picked up on the hands of others and spread further. People catch the virus when they tough their infected hands to their mouth, nose or eyes. Standard recommendations to prevent infection include regular hand washing, covering mouth and nose when coughing and sneezing, thoroughly cooking meat and eggs. Avoid close contact with anyone showing symptoms or respiratory illness such as coughing and sneezing.

Various crazy conspiracy theories have been circulating that the virus somehow escaped from a Chinese lab, either by accident or design. However, that is categorically untrue and scientists studying its genetic code have linked it to bats. It probably then jumped to another animal, which passed it on to humans.

The 1918 Spanish Influenza or the H1N1 virus remains the most devastating flu pandemic in the modern history. The disease swept around the globe and is estimated to have caused between 50 to 100 million deaths. A version of the same virus was also behind the 2009 swine flu outbreak, thought to have killed as many as 575,400 people.

Other major influenza outbreaks include Asian flu in 1957, which led to roughly 2 million deaths, and Hong Kong flu which killed 1 million people 11 years later.

But coronavirus outbreaks have so far been far smaller. Sars eventually spread to 27 countries in total, infecting around 8000 people and killing 700