Journey

The text is about DNA spiking and the selector technique in genetics.

DNA spiking refers to the different ratio of bases at a single position when synthesizing oligonucleotides. It can be equal or unequal proportions of bases at a given position. In PCR, DNA spiking is a spike control where DNA is added to a sample to see if the reaction will amplify and to discover any malfunctions in the PCR machine.

The selector technique is a method to amplify and multiplex genomic DNA by circularizing it with a vector sequence through hybridization and ligation. A selector consists of two oligonucleotides and works by a selector probe hybridizing with both ends of the target.

DNA polymerase is an enzyme that synthesizes DNA molecules from deoxyribonucleotides and is essential for DNA replication. It adds nucleotides to the 3′ end of a DNA strand, one at a time, and is required for cell division. DNA polymerase I was discovered by Arthur Kornberg in 1956, and DNA polymerase II was discovered by Thomas Kornberg and Malcolm E. Gefter in 1970. The main function of DNA polymerase is to synthesize DNA from deoxyribonucleotides, while RNA polymerases synthesize RNA from ribonucleotides.

Main Points:

• DNA spiking refers to the different ratio of bases when synthesizing oligonucleotides.
• In PCR, DNA spiking is a spike control to see if the reaction will amplify and discover any malfunctions.
• The selector technique is a method to amplify and multiplex genomic DNA.
• A selector consists of two oligonucleotides and works by a selector probe hybridizing with both ends of the target.
• DNA polymerase is an enzyme that synthesizes DNA molecules and is essential for DNA replication.
• DNA polymerase I and II were discovered by Arthur Kornberg and Thomas Kornberg and Malcolm E. Gefter, respectively.
• The main function of DNA polymerase is to synthesize DNA, while RNA polymerases synthesize RNA.

The text describes the shape and function of DNA polymerases in DNA replication. DNA polymerases have a conserved structure and resemble a right hand with thumb, finger, and palm domains. The palm domain functions in catalyzing the transfer of phosphoryl groups, the finger domain functions in binding nucleoside triphosphates with the template base, and the thumb domain plays a potential role in processivity, translocation, and positioning. DNA polymerases can be processive or nonprocessive and have varying degrees of processivity proportional to the rate of DNA synthesis. DNA polymerases can be further subdivided into seven different families and some viruses also encode special DNA polymerases such as reverse transcriptase. Prokaryotic polymerases exist in two forms, core polymerase and holoenzyme.

Main Points:

• DNA polymerases have a conserved structure resembling a right hand with thumb, finger, and palm domains.
• The palm domain catalyzes the transfer of phosphoryl groups, the finger domain binds nucleoside triphosphates with the template base, and the thumb domain plays a potential role in processivity, translocation, and positioning.
• DNA polymerases can be processive or nonprocessive and have varying degrees of processivity proportional to the rate of DNA synthesis.
• DNA polymerases can be further subdivided into seven different families and some viruses encode special DNA polymerases such as reverse transcriptase.
• Prokaryotic polymerases exist in two forms, core polymerase and holoenzyme.

The text describes the different families of DNA polymerases and their properties and functions. The Family D of DNA polymerase was discovered in Pyrococcus furiosus and Methanococcus jannaschii and is different from other DNA polymerases in terms of its structure and mechanism, which resembles that of multi-subunit RNA polymerases. The Pyrococcus abyssi polD is more heat-stable and more accurate than Taq polymerase but is yet to be commercialized. Family X polymerases are mainly found in vertebrates and have highly conserved regions that are involved in DNA-polymerase interactions. Different members of this family are involved in DNA repair mechanisms. Family B polymerases are the main polymerases involved in nuclear DNA replication. The Pol ? complex is made up of four subunits and is involved in replicating the leading strand of DNA during replication, while Pol ? primarily replicates the lagging strand. However, recent evidence suggests that Pol ? might have a role in replicating the leading strand as well.

Main points:

• The Family D of DNA polymerase was discovered in Pyrococcus furiosus and Methanococcus jannaschii.
• The Pyrococcus abyssi polD is more heat-stable and more accurate than Taq polymerase.
• Family X polymerases are mainly found in vertebrates and are involved in DNA repair mechanisms.
• Family B polymerases are the main polymerases involved in nuclear DNA replication.
• The Pol ? complex is involved in replicating the leading strand of DNA, while Pol ? replicates the lagging strand.
• Recent evidence suggests that Pol ? might have a role in replicating the leading strand as well.

The text discusses the concept of denaturation of proteins or nucleic acids and how it affects the functioning of these biomolecules. Denaturation occurs when a protein or nucleic acid loses its quaternary, tertiary, and secondary structures due to external stressors like heat, acids, or salts. The folding of proteins is crucial for their functioning, and denaturation can cause proteins to lose their 3D shape and hence their ability to function. The folding of a protein depends on a balance between weak intramolecular interactions and protein-solvent interactions. This process can be affected by environmental conditions like temperature, salinity, pressure, and solvents.

Main points:

• Denaturation is the process of losing the quaternary, tertiary, and secondary structures of proteins or nucleic acids
• Causes include heat, acids, salts, organic solvents, radiation, etc.
• Protein denaturation can result in disruption of cell activity and possibly cell death
• Protein folding is key to the functioning of proteins and depends on a balance between intramolecular interactions and protein-solvent interactions
• Environmental conditions like temperature, salinity, pressure, and solvents can affect the folding of proteins and lead to denaturation

The denaturation of DNA is the process of breaking the non-covalent interactions between the antiparallel strands of DNA, causing the double helix to “open”. The first model to describe the thermodynamics of the denaturation process was introduced in 1966, but it is now considered limited and recent studies have provided more information on the lifetime of a denaturation bubble. DNA can be denatured by heat, as well as chemical agents like formamide, guanidine, and sodium salicylate. These agents lower the melting temperature by competing for hydrogen bond donors and acceptors, and some are able to induce denaturation at room temperature. Alkaline agents like NaOH can denature DNA by changing pH and removing hydrogen-bond contributing protons.

Main Points:

• Denaturation of DNA is the process of breaking non-covalent interactions between antiparallel strands.
• The Poland-Scheraga Model is the first to describe the thermodynamics of denaturation, but it is considered limited.
• Recent studies have inferred the lifetime of a singular denaturation bubble ranges from 1 microsecond to 1 millisecond.
• DNA can be denatured by heat or chemical agents like formamide, guanidine, and sodium salicylate.
• Chemical agents lower the melting temperature by competing for hydrogen bond donors and acceptors.
• Alkaline agents like NaOH can denature DNA by changing pH and removing hydrogen-bond contributing protons.

The text describes the denaturation of nucleic acids and proteins, and different methods and agents used for this process.

Main Points:

• Chemical denaturation can provide a gentler procedure for denaturing nucleic acids than heat denaturation.
• Air can weaken the hydrogen bonding in DNA and lead to denaturation.
• Understanding the properties of nucleic acid denaturation has led to the development of laboratory techniques such as PCR, Southern blot, Northern blot, and DNA sequencing.
• Different denaturants including acids, bases, solvents, cross-linking reagents, chaotropic agents, disulfide bond reducers, chemically reactive agents, and mechanical agitation can be used for protein denaturation.
• Chemical nucleic acid denaturants include acids and bases, as well as other agents like DMSO, formamide, and guanidine.
• Physical methods for denaturation include thermal denaturation, beads mill, probe sonication, and radiation.

The reverse transcriptase (RT) is an enzyme used for reverse transcription, the process of generating complementary DNA (cDNA) from RNA. RT is used by various viruses, retroviruses, and eukaryotic cells for replication, proliferation, or telomere maintenance. Reverse transcriptases have three sequential activities of RNA-dependent DNA polymerase, ribonuclease H (RNAse H), and DNA-dependent DNA polymerase that enable the conversion of single-stranded RNA into double-stranded cDNA. Reverse transcriptases were discovered by Howard Temin and David Baltimore, who shared the 1975 Nobel Prize in Physiology or Medicine. Well-known RTs include HIV-1 reverse transcriptase, M-MLV reverse transcriptase, and telomerase reverse transcriptase.

Main Points:

• Reverse transcriptase is an enzyme used in reverse transcription.
• It is used by various viruses, retroviruses, and eukaryotic cells for replication, proliferation, or telomere maintenance.
• RT has three sequential activities: RNA-dependent DNA polymerase, ribonuclease H (RNAse H), and DNA-dependent DNA polymerase.
• Reverse transcriptases were discovered by Howard Temin and David Baltimore.
• Well-known RTs include HIV-1 reverse transcriptase, M-MLV reverse transcriptase, and telomerase reverse transcriptase.

Dot-form list:

• RT is an enzyme for reverse transcription.
• RT is used by viruses, retroviruses, and eukaryotic cells for replication, proliferation, or telomere maintenance.
• RT has RNA-dependent DNA polymerase, RNAse H, and DNA-dependent DNA polymerase activities.
• RTs were discovered by Temin and Baltimore.
• Well-known RTs include HIV-1, M-MLV, and telomerase RT.

The reverse transcriptase is a crucial component of the replication process of retroviruses. It has a right hand structure similar to other viral nucleic acid polymerases and a domain belonging to the RNase H family. The reverse transcriptase degrades the RNA template, allowing the other strand of DNA to be synthesized. There are three replication systems in the life cycle of a retrovirus, each with the potential to cause mutations. The reverse transcriptase has a high error rate in transcribing RNA to DNA, leading to an accelerated accumulation of mutations. Reverse transcriptases have also been shown to be involved in transcript fusions, exon shuffling, and artificial antisense transcrip

Main Points:

• Reverse transcriptase is a crucial component of the replication process of retroviruses.
• It has a right hand structure similar to other viral nucleic acid polymerases and a domain belonging to the RNase H family.
• The reverse transcriptase degrades the RNA template, allowing the other strand of DNA to be synthesized.
• There are three replication systems in the life cycle of a retrovirus, each with the potential to cause mutations.
• The reverse transcriptase has a high error rate in transcribing RNA to DNA, leading to an accelerated accumulation of mutations.
• Reverse transcriptases have also been shown to be involved in transcript fusions, exon shuffling, and artificial antisense transcripts.

The text provides information on the use of antiviral drugs against the replication of the human immunodeficiency virus (HIV). These drugs, known as reverse transcriptase inhibitors, target the reverse transcriptase enzyme that is used by the retrovirus to copy its genetic material and generate new viruses. The drugs include nucleoside and nucleotide analogues (such as zidovudine and lamivudine) and non-nucleoside inhibitors (such as nevirapine).

Main points:

• HIV uses reverse transcriptase to replicate
• Antiviral drugs are called reverse transcriptase inhibitors
• Reverse transcriptase inhibitors target the replication process of HIV
• Examples of reverse transcriptase inhibitors include nucleoside and nucleotide analogues and non-nucleoside inhibitors

The text describes the molecular biology techniques of reverse transcription polymerase chain reaction (RT-PCR) and polymerase chain reaction (PCR). Reverse transcriptase is used to transcribe RNA into DNA, making it possible to apply PCR to RNA, and to create cDNA libraries. Reverse transcriptase has also been used to create insulin by inserting eukaryotic mRNA into bacteria and converting the edited RNA into DNA. PCR involves in vitro amplification of specific nucleic acid sequences using a heat-stable DNA polymerase such as Taq DNA polymerase. The basic steps of PCR are denaturation, annealing of specific primers, and extension by the DNA polymerase. This process is repeated many times to amplify the DNA.

Dot form list:

• Reverse transcription polymerase chain reaction (RT-PCR) involves transcribing RNA into DNA with reverse transcriptase for PCR analysis.
• Reverse transcriptase creates cDNA libraries and is used in insulin production.
• Polymerase chain reaction (PCR) involves in vitro amplification of specific nucleic acid sequences.
• The basic steps of PCR are denaturation, annealing of specific primers, and extension by the DNA polymerase.
• The reaction is repeated many times to amplify the DNA.

The text describes Polymerase Chain Reaction (PCR), a technique invented by Kary Mullis in the early 1980s that amplifies pieces of DNA by several orders of magnitude. The components of a PCR reaction include a DNA template, primers, nucleotides, DNA polymerase, and a buffer. The DNA template is usually the sample DNA that contains the DNA region to be amplified and could be plasmid DNA, genomic DNA, or tissue. Primers are short oligonucleotides of DNA with a specific sequence that is custom synthesized and match to the two ends of the segment of DNA to be amplified. The primer design is critical for a successful PCR reaction.

Main points:

• PCR is a technique for amplifying pieces of DNA by several orders of magnitude.
• The components of a PCR reaction include a DNA template, primers, nucleotides, DNA polymerase, and a buffer.
• The DNA template is usually the sample DNA containing the DNA region to be amplified.
• Primers are short oligonucleotides of DNA with a specific sequence custom synthesized to match the two ends of the segment of DNA to be amplified.
• Primer design is critical for a successful PCR reaction.

The text describes the steps and components involved in a polymerase chain reaction (PCR) procedure. DNA polymerase is an enzyme that amplifies DNA during cell cycles in living organisms. The procedure uses Taq polymerase, a type of DNA polymerase that can tolerate high temperatures, along with nucleotides, PCR buffers, and other components, which are added to the reaction in specific concentrations. A typical PCR procedure takes place in an automated thermal cycler machine, with a series of repeated cycles of denaturation, annealing, and elongation at specific temperatures. The text also provides general guidelines for programming a typical PCR reaction in an automated thermal cycler machine.

Main points:

• DNA polymerase is an enzyme that amplifies DNA in cell cycles
• Taq polymerase is a type of DNA polymerase used in PCR that can tolerate high temperatures
• Nucleotides, PCR buffers, and other components are added to the reaction in specific concentrations
• A typical PCR procedure takes place in an automated thermal cycler machine
• The procedure consists of repeated cycles of denaturation, annealing, and elongation at specific temperatures
• General guidelines for programming a typical PCR reaction in a thermal cycler machine are provided

(What does this mean? “In PCR reactions, a mixture of four types of nucleotides (ATP, CTP, GTP, TTP; known as dNTPs) will be added.”)

In PCR reactions, a mixture of four types of nucleotides (ATP, CTP, GTP, TTP) will be added, also known as dNTPs.

(Wouldn’t adding 4 mixtures of nucleotides contaminate the sample?)

No, the addition of four types of nucleotides in a mixture, referred to as dNTPs, is a necessary part of the PCR reaction and does not contaminate the sample. The DNA polymerase will grab the complementary nucleotides from the mixture and attach them to the 3′ end of the primer to pair with the template DNA.

(How does adding all these different compounds—primers, nucleotides, and who knows what else—not “contaminate” the sample? It makes no sense.)

Adding all the different components does not necessarily result in contamination of the sample. Contamination can occur when there is an unintended source of DNA present in the reaction. In PCR, specific steps are taken to minimize the risk of contamination such as using sterile techniques, using positive control samples, and using dedicated laboratory equipment. The components added to a PCR reaction are chosen and optimized to enhance the desired specific DNA amplification, and the reaction conditions and thermal cycling steps help to selectively target and amplify only the specific DNA of interest.

(How would they know that they are not just amplifying any of these compounds and “assuming” its DNA?)

The specificity of the PCR reaction and the primers used for the reaction ensure that only the target DNA sequence is amplified, and not other contaminants or non-target DNA. The primers are designed to bind specifically to the target DNA sequence, and the temperature cycles in the reaction cause the complementary nucleotides to bind to the primers and the target DNA, allowing the DNA polymerase to extend the primers and form a new DNA strand. The high specificity of the reaction helps to minimize the amplification of non-target DNA or contaminants.

The text describes the invention of polymerase chain reaction (PCR) by Dr. Kary Mullis, who received a Nobel Prize in Chemistry for his invention. PCR assays have been developed to detect T. pallidum subspecies nucleic acids and have been used to distinguish nonvenereal T. pallidum subspecies. PCR detection of Epstein-Barr Virus (EBV) DNA in the central nervous system has been useful in diagnosing CNS lymphoma in patients with HIV. The quantification of EBV DNA in the central nervous system fluid may also be useful for monitoring therapy effects.

Main points:

• Dr. Kary Mullis invented PCR and received a Nobel Prize in Chemistry for his invention
• PCR assays have been developed for T. pallidum nucleic acids detection and for distinguishing nonvenereal T. pallidum subspecies
• PCR detection of EBV DNA in CSF is useful in diagnosing CNS lymphoma in HIV patients
• Quantification of EBV DNA in CSF may also be useful for monitoring therapy effects.