DNA-DNA Hybridization

DNA-DNA Hybridization

DNA-DNA hybridization generally refers to a molecular biology technique that measures the degree of genetic similarity between pools of DNA sequences. It is usually used to determine the genetic distance between two species. When several species are compared that way, the similarity values allow the species to be arranged in a phylogenetic tree; it is therefore one possible approach to carrying out molecular systematics.

Charles Sibley and Jon Ahlquist, pioneers of the technique, used DNA-DNA hybridization to examine the phylogenetic relationships of avians (the Sibley-Ahlquist taxonomy) and primates.Critics argue that the technique is inaccurate for comparison of closely related species, as any attempt to measure differences between orthologous sequences between organisms is overwhelmed by the hybridization of paralogous sequences within an organism's genome.DNA sequencing and computational comparisons of sequences is now generally the method for determining genetic distance, although the technique is still used in microbiology to help identify bacteria.
The DNA of one organism is labeled, then mixed with the unlabeled DNA to be compared against. The mixture is incubated to allow DNA strands to dissociate and reanneal, forming hybrid double-stranded DNA. Hybridized sequences with a high degree of similarity will bind more firmly, and require more energy to separate them: i.e. they separate when heated at a higher temperature than dissimilar sequences, a process known as "DNA melting".

To assess the melting profile of the hybridized DNA, the double-stranded DNA is bound to a column and the mixture is heated in small steps. At each step, the column is washed; sequences that melt become single-stranded and wash off the column. The temperatures at which labeled DNA comes off the column reflects the amount of similarity between sequences (and the self-hybridization sample serves as a control). These results are combined to determine the degree of genetic similarity between organisms.

DNA Repair

DNA Repair

DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light and radiation can cause DNA damage, resulting in as many as 1 million individual molecular lesions per cell per day.Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell's ability to transcribe the gene that the affected DNA encodes. Other lesions induce potentially harmful mutations in the cell's genome, which affect the survival of its daughter cells after it undergoes mitosis. Consequently, the DNA repair process is constantly active as it responds to damage in the DNA structure. When normal repair processes fail, and when cellular apoptosis does not occur, irreparable DNA damage may occur, including double-strand breaks and DNA crosslinkages.
The rate of DNA repair is dependent on many factors, including the cell type, the age of the cell, and the extracellular environment. A cell that has accumulated a large amount of DNA damage, or one that no longer effectively repairs damage incurred to its DNA, can enter one of three possible states:

1. Irreversible state of dormancy, known as senescence
2. Cell suicide, also known as apoptosis or programmed cell death
3. Unregulated cell division, which can lead to the formation of a tumor that is cancerous

The DNA repair ability of a cell is vital to the integrity of its genome and thus to its normal functioning and that of the organism. Many genes that were initially shown to influence life span have turned out to be involved in DNA damage repair and protection.Failure to correct molecular lesions in cells that form gametes can introduce mutations into the genomes of the offspring and thus influence the rate of evolution.

DNA forensics

DNA forensics



The sequence of all species of organisms can be identified by studying the DNA that is unique to this species. Identify individuals within the species is less accurate on the site, but if DNA sequencing technology, further development of direct comparison with the large DNA and possibly the entire genome of a viable and practical and allows you to clearly separate identity.

Identifying persons forensic scan 13 loci, or regions, which vary from person to person and use these data to create a DNA profile of the person (also called DNA fingerprinting). There is very little chance that another person with the same DNA profile of a specific set of 13 regions.

Some examples of the use of DNA for forensic identification

* Identification of the suspects, who can match DNA evidence left at the crime scene sites
* People to exclude falsely accused of crimes
* Recognition of victims of crime and natural disasters
* Establishment of paternity and other family relationships
* When determining the risk and protected species as an aid to wildlife officials can (be used for prosecuting poachers)
Detection of bacteria and other microorganisms that may contaminate air, water, soil and food
* Party organ donors with recipients in transplant programs
* Place rocks seeds or livestock
* The authenticity of food as caviar and wine

DNA is effective in identifying people?

DNA identification can be very effective if it is used to make sense. Parts should be changing the DNA sequence between the most use, in addition, the parties must be large NOK overcome the fact that the man is completely random mating.

Included in the State to investigate the crime. . .

We assume that blood is the conclusion to the scene. Type O occurs in approximately 45% of Americans. If investigators type only for ABO, finding that the suspect in a crime type O really does not talk too much.

If, in addition to the type of Ø, the suspect blond, blond and questions, you now have two pieces of evidence suggest that it was in reality. Nevertheless, there are a number of type O is a blonde.

If you are at the crime scene traces from a pair of Nike Air Jordan (unique design of the herd) and the suspect, because type O and blond, Air Jordan also works the same design of the crowd much closer to the samples of the suspect to the scene.

Thus, to collect evidence of a link in the chain, where each bit is not even a strong, but the version of each of them, very strong, we can say that they doubt that the human rights.

Since DNA is the same type of thinking, which is used, you can search for matches (on the basis of the order, or if the number of small repeating units of DNA sequences) in different locations in the human genome, one or two (even three) NOK not be sure that the right course, and thirteen sites use. Rare appearances in all twelve good that you (or perhaps the prosecutor or the jury) the strengthening of trust ( "beyond reasonable doubt") argue that human rights.

How DNA typing done?

But the tenth of a percent of DNA (about 3 million bases) differs from one person to another. Researchers can use the variable regions to create a DNA profile of the person, using samples of blood, bones, hair and other body tissues and products.

In criminal cases in question, as a rule, get samples of evidence from the crime and suspicious cases, DNA extraction and analysis of the current set of specific regions of DNA (markers).

Scientists find evidence of DNA samples through the development of small pieces of DNA (probes) that each query, and bind to complementary sequences of DNA in the sample. Creates a number of investigations related to the specific structure of the samples of human DNA. The scientists compare the DNA profiles of the law to determine appropriate evidence test sample. Mark himself, as a rule, not only for the individual, but in two samples of DNA that are similar to four or five regions, most likely that the samples of the same person.

If the sample does not match the profile, not the person placing the DNA at the crime scene.

If the nature of the suspect can be assisted in the sample. Although the likelihood that another person with the same DNA profile of a specific set of probe, the chances are very small. Q: How small probability must be convinced of the guilt or acquittal of the innocent right? Judges consider many of the materials in the jury considered in conjunction with other evidence in the case. Experts say that the technology of recombinant DNA-based forensic best of witnesses, where the probability of a correct definition in 50:50.

More probes used in DNA analysis, most likely from a template, and the occasional match, but each one must probe further increases the time and cost of testing.Recommended four to six sensors. Try to get some more conventional probes, observed John Hicks (Alabama State Department legal services). He predicted that the DNA chip technology (in thousands of short sequences of DNA data to insert a small chip) will be done much faster economic analysis using probes much larger and increases the probability of intersection of the parties.

What are some of the field of DNA technologies used in forensic investigations?

Excerpts restrictions Polymorphism (RFLP)
RFLP technique to analyze a variable length of DNA fragments resulting from digestion of DNA samples from a special type of enzymes. This enzyme, restriction endonuclease meetings on specific model of DNA sequences, known as restriction endonuclease recognition site. Creates the presence or absence of specific recognition sites in DNA of different length DNA fragments separated by electrophoresis education. Thus hybridization with DNA probes linked to the complementary sequences of DNA in the sample.

RFLP was one of the first applications of DNA analysis in forensic investigations. With the development of new and more efficient DNA-analysis techniques, RFLP is not used as much as it was before, because it requires relatively large amounts of DNA. In addition, samples of degraded environmental factors, such as dirt, and mildew, do not work well with RFLP.

PCR
Was used for chain reaction (PCR) to make millions of exact copies of DNA from biological samples. DNA amplification by polymerase chain reaction can analyze DNA from biological samples as small as a few skin cells. For RFLP, if the amount of quarter samples of DNA. The ability of PCR for amplification of small amounts of degraded DNA samples is the analysis. Care, however, should be adopted in order to prevent contamination with other biological material to identify, collect and preserve samples.

Street Analysis
SSR (str) technology is used to evaluate specific regions (loci) in the nuclear DNA. The diversity of regions, size can be used to distinguish one DNA profile from another. Federal Bureau of Investigation (FBI) uses a standard set of specific regions from 13 to St. CODIS. CODIS is a program that controls the local state and national DNA databases of convicted persons, unsolved crime scene and evidence of missing persons. The probability that two individuals of the same 13 loci of a profile in one billion.

Analysis of mitochondrial DNA
Analysis of mitochondrial DNA (mtDNA) can be used to study DNA samples can be analyzed by RFLP or size. Nuclear DNA must be extracted from the samples for use in RFLP, PCR, and size, however, mtDNA analysis uses DNA extracted from other cellular organelles mitochondria. Although adult biological samples may be missing the main cell materials, such as hair, bones and teeth, which analyzed the numbers and RFLP, could be analyzed with mtDNA. During the investigation, the case went unsolved for many years, mtDNA is extremely valuable.

All mothers are the same mitochondrial DNA to their children. This is because the mitochondria of each new embryo from the egg mother. Father's sperm contributes only nuclear DNA. Compared with the profile of mtDNA remain unknown to the profile of a potential maternal relative can be an important technique with the lack of research on human beings.

Y-chromosome analysis
Y-chromosome is passed directly from father to son, so that the analysis of genetic markers on the Y chromosome is especially useful for tracking relationships between men and for analysis of biological evidence involving multiple male contributors.

DNA-Binding Proteins

DNA-Binding Proteins

Structural proteins that bind DNA are well-understood examples of non-specific DNA-protein interactions. Within chromosomes, DNA is held in complexes with structural proteins. These proteins organize the DNA into a compact structure called chromatin. In eukaryotes this structure involves DNA binding to a complex of small basic proteins called histones, while in prokaryotes multiple types of proteins are involved.The histones form a disk-shaped complex called a nucleosome, which contains two complete turns of double-stranded DNA wrapped around its surface. These non-specific interactions are formed through basic residues in the histones making ionic bonds to the acidic sugar-phosphate backbone of the DNA, and are therefore largely independent of the base sequence.Chemical modifications of these basic amino acid residues include methylation, phosphorylation and acetylation.These chemical changes alter the strength of the interaction between the DNA and the histones, making the DNA more or less accessible to transcription factors and changing the rate of transcription. Other non-specific DNA-binding proteins in chromatin include the high-mobility group proteins, which bind to bent or distorted DNA. These proteins are important in bending arrays of nucleosomes and arranging them into the larger structures that make up chromosomes.


A distinct group of DNA-binding proteins are the DNA-binding proteins that specifically bind single-stranded DNA. In humans, replication protein A is the best-understood member of this family and is used in processes where the double helix is separated, including DNA replication, recombination and DNA repair.These binding proteins seem to stabilize single-stranded DNA and protect it from forming stem-loops or being degraded by nucleases.
The lambda repressor helix-turn-helix transcription factor bound to its DNA target
In contrast, other proteins have evolved to bind to particular DNA sequences. The most intensively studied of these are the various transcription factors, which are proteins that regulate transcription. Each transcription factor binds to one particular set of DNA sequences and activates or inhibits the transcription of genes that have these sequences close to their promoters. The transcription factors do this in two ways. Firstly, they can bind the RNA polymerase responsible for transcription, either directly or through other mediator proteins; this locates the polymerase at the promoter and allows it to begin transcription. Alternatively, transcription factors can bind enzymes that modify the histones at the promoter; this will change the accessibility of the DNA template to the polymerase.


As these DNA targets can occur throughout an organism's genome, changes in the activity of one type of transcription factor can affect thousands of genes.Consequently, these proteins are often the targets of the signal transduction processes that control responses to environmental changes or cellular differentiation and development. The specificity of these transcription factors' interactions with DNA come from the proteins making multiple contacts to the edges of the DNA bases, allowing them to "read" the DNA sequence. Most of these base-interactions are made in the major groove, where the bases are most accessible

Ways of giving Chemotherapy

Ways of giving Chemotherapy

Depending on the type of cancer, chemotherapy can be administered orally or intravenously (directly into the vein).

* Chemotherapy Oral (swallowing tablets)

These are in the form of tablets. If the health of the patient allows, he / she is able to put them into the house. Nevertheless, regular visits to hospitals are still needed to check on the health of the patient and the response to treatment.

It is vital for making tablets directly at specified. If the t forget to take one patient at a given time he / she should call the medical staff immediately.

* Chemotherapy intravenous (directly into the vein)

Intravenous chemotherapy can be given as follows:

o The direct injection into a vein.
o By drip (intravenous infusion).
o Three or infusion pump.
o Three pumps the patient bears for several weeks or months. This is known as continuous infusion, venous infusion fadálach, or ambulatory infusion (the patient may progress during the reception of the medication resources).

There are several ways to medication in the patient. These include:

o cannula - a thin tube is inserted through the skin into the vein - usually the body that comes through the back of the hand or low hand.

o infusion (intravenous infusion) - in order to dilute the medication may be rare in the bag. The solution in the bag through a tube in the hands of patients and in the vein (intravenous infusion). Cannula will be used. The solution slowly into the vein.

Chemotherapy by pressure are generally dripping from the pump. Do not hurry the pumping of the process, instead causes the solution into the vein at constant speed in a given period - the slower the rate, the longer it will take the whole thing.

o Central line - this is a long, flexible plastic line (thin tube) to come into the center of blood vessels in the chest, near the heart. The central line is usually the body goes through the center of the chest under the skin and increases in large artery near the collarbone (clavicle). The only visible part of the length of a line from the date is a little hole in the chest.

o peripherally inserted central catheter (PICC) line - the long, thin, flexible tube that is required in a vein, usually in the arm and makes its way into a large vein in the fund is near the heart. It is like a central line, but has a different point of entry.

o portacath (implantable ports) - which, for thin soft, flexible plastic tube going into a vein. It is the port (opening) just under the skin of the fund or arm. The port on which thin rubber disc special needles to pass a medical, or taken from the blood.

Pregnancy and contraception
Many chemotherapy drugs can cause birth defects. It is important to prevent a pregnant woman chemotherapy. Since most chemotherapy drugs in oral contraceptives is important to use a barrier method of contraception such as condoms, during the entire period of chemotherapy treatment and for years after treatment completion. If you are pregnant, you should tell the medical staff immediately prior. If you fall pregnant during treatment immediately tell the medical staff.