What is genetic testing and gel electrophoresis???

Answer 1

Genetic testing
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Genetic testing allows the genetic diagnosis of vulnerabilities to inherited diseases, and can also be used to determine a person's ancestry. Every person carries two copies of every gene, one inherited from their mother, one inherited from their father. The human genome is believed to contain around 25,000 - 35,000 genes. In addition to studying chromosomes to the level of individual genes, genetic testing in a broader sense includes biochemical tests for the possible presence of genetic diseases, or mutant forms of genes associated with increased risk of developing genetic disorders. Genetic testing identifies changes in chromosomes, genes, or proteins. Most of the time, testing is used to find changes that are associated with inherited disorders. The results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person's chance of developing or passing on a genetic disorder. Several hundred genetic tests are currently in use, and more are being developed.

Since genetic testing may open up ethical or psychological problems, genetic testing is often accompanied by genetic counseling.
Contents
[hide]

* 1 Types
* 2 Medical procedure
o 2.1 Interpreting results
* 3 Cost and time
* 4 Benefits
* 5 Risks and limitations
* 6 Testing
* 7 Direct-to-Consumer (DTC) Genetic Testing
o 7.1 Controversy
o 7.2 Government Regulation
* 8 Fiction
* 9 See also
* 10 References
* 11 External links

[edit] Types

Genetic testing is "the analysis of human DNA, RNA, chromosomes, proteins, and certain metabolites in order to detect heritable disease-related genotypes, mutations, phenotypes, or karyotypes for clinical purposes " (Holtzman & Watson 1997). It can provide information about a person's genes and chromosomes throughout life. Available types of testing include:

* Newborn screening: Newborn screening is used just after birth to identify genetic disorders that can be treated early in life. The routine testing of infants for certain disorders is the most widespread use of genetic testing—millions of babies are tested each year in the United States. All states currently test infants for phenylketonuria (a genetic disorder that causes mental retardation if left untreated) and congenital hypothyroidism (a disorder of the thyroid gland).
* Diagnostic testing: Diagnostic testing is used to diagnose or rule out a specific genetic or chromosomal condition. In many cases, genetic testing is used to confirm a diagnosis when a particular condition is suspected based on physical mutations and symptoms. Diagnostic testing can be performed at any time during a person's life, but is not available for all genes or all genetic conditions. The results of a diagnostic test can influence a person's choices about health care and the management of the
* Carrier testing: Carrier testing is used to identify people who carry one copy of a gene mutation that, when present in two copies, causes a genetic disorder. This type of testing is offered to individuals who have a family history of a genetic disorder and to people in ethnic groups with an increased risk of specific genetic conditions. If both parents are tested, the test can provide information about a couple's risk of having a child with a genetic condition.
* Prenatal testing: Prenatal testing is used to detect changes in a fetus's genes or chromosomes before birth. This type of testing is offered to couples with an increased risk of having a baby with a genetic or chromosomal disorder. In some cases, prenatal testing can lessen a couple's uncertainty or help them decide whether to abort the pregnancy. It cannot identify all possible inherited disorders and birth defects, however.
* Predictive and presymptomatic testing: Predictive and presymptomatic types of testing are used to detect gene mutations associated with disorders that appear after birth, often later in life. These tests can be helpful to people who have a family member with a genetic disorder, but who have no features of the disorder themselves at the time of testing. Predictive testing can identify mutations that increase a person's chances of developing disorders with a genetic basis, such as certain types of cancer. For example, an individual with a mutation in BRCA1 has a 65% cumulative risk of breast cancer [1]. Presymptomatic testing can determine whether a person will develop a genetic disorder, such as hemochromatosis (an iron overload disorder), before any signs or symptoms appear. The results of predictive and presymptomatic testing can provide information about a person’s risk of developing a specific disorder and help with making decisions about medical care.
* Forensic testing: Forensic testing uses DNA sequences to identify an individual for legal purposes. Unlike the tests described above, forensic testing is not used to detect gene mutations associated with disease. This type of testing can identify crime or catastrophe victims, rule out or implicate a crime suspect, or establish biological relationships between people (for example, paternity).
* Research testing: Research testing include finding unknown genes, learning how genes work and advancing our understanding of genetic conditions. The results of testing done as part of a research study are usually not available to patients or their healthcare providers.

[edit] Medical procedure

Genetic testing is often done as part of a genetic consultation. Once a person decides to proceed with genetic testing, a medical geneticist, genetic counselor, primary care doctor, or specialist can order the test after obtaining informed consent.

Genetic tests are performed on a sample of blood, hair, skin, amniotic fluid (the fluid that surrounds a fetus during pregnancy), or other tissue. For example, a medical procedure called a buccal smear uses a small brush or cotton swab to collect a sample of cells from the inside surface of the cheek. The sample is sent to a laboratory where technicians look for specific changes in chromosomes, DNA, or proteins, depending on the suspected disorder. The laboratory reports the test results in writing to a person's doctor or genetic counselor.

Routine newborn screening tests are done on a small blood sample, using a 'heel stick', by pricking the babies heel and blotting the blood on a special paper. Unlike other types of genetic testing, a parent will usually only receive the result if it is positive.

[edit] Interpreting results

The results of genetic tests are not always straightforward, which often makes them challenging to interpret and explain. When interpreting test results, healthcare professionals consider a person’s medical history, family history, and the type of genetic test that was done.

A positive test result means that the laboratory found a change in a particular gene, chromosome, or protein of interest. Depending on the purpose of the test, this result may confirm a diagnosis, indicate that a person is a carrier of a particular genetic mutation, identify an increased risk of developing a disease (such as cancer) in the future, or suggest a need for further testing. Because family members have some genetic material in common, a positive test result may also have implications for certain blood relatives of the person undergoing testing. It is important to note that a positive result of a predictive or presymptomatic genetic test usually cannot establish the exact risk of developing a disorder. Also, health professionals typically cannot use a positive test result to predict the course or severity of a condition.

A negative test result means that the laboratory did not find a dangerous copy of the gene, chromosome, or protein under consideration. This result can indicate that a person is not affected by a particular disorder, is not a carrier of a specific genetic mutation, or does not have an increased risk of developing a certain disease. It is possible, however, that the test missed a disease-causing genetic alteration because many tests cannot detect all genetic changes that can cause a particular disorder. Further testing may be required to confirm a negative result.

In some cases, a negative result might not give any useful information. This type of result is called uninformative, indeterminate, inconclusive, or ambiguous. Uninformative test results sometimes occur because everyone has common, natural variations in their DNA, called polymorphisms, that do not affect health. If a genetic test finds a change in DNA that has not been associated with a disorder in other people, it can be difficult to tell whether it is a natural polymorphism or a disease-causing mutation. An uninformative result cannot confirm or rule out a specific diagnosis, and it cannot indicate whether a person has an increased risk of developing a disorder. In some cases, testing other affected and unaffected family members can help clarify this type of result.

[edit] Cost and time

The cost of genetic testing can range from under $100 to more than $2,000, depending on the nature and complexity of the test. The cost increases if more than one test is necessary or if multiple family members must be tested to obtain a meaningful result. In countries with private health insurance, in many cases, health insurance plans will cover the costs of genetic testing when it is recommended by a person's doctor.

From the date that a sample is taken, it may take a few weeks to several months to receive the test results. Results for prenatal testing are usually available more quickly because time is an important consideration in making decisions about a pregnancy.

[edit] Benefits

Genetic testing has potential benefits whether the results are positive or negative for a gene mutation. Test results can provide a sense of relief from uncertainty and help people make informed decisions about managing their health care. For example, a negative result can eliminate the need for unnecessary checkups and screening tests in some cases. A positive result can direct a person toward available prevention, monitoring, and treatment options. Some test results can also help people make decisions about having children. Newborn screening can identify genetic disorders early in life so treatment can be started as early as possible.

[edit] Risks and limitations

The physical risks associated with most genetic tests are very small, particularly for those tests that require only a blood sample or buccal smear (a procedure that samples cells from the inside surface of the cheek). The procedures used for prenatal testing carry a small but real risk of losing the pregnancy (miscarriage) because they require a sample of amniotic fluid or tissue from around the fetus.

Many of the risks associated with genetic testing involve the emotional, social, or financial consequences of the test results. People may feel angry, depressed, anxious, or guilty about their results. In some cases, genetic testing creates tension within a family because the results can reveal information about other family members in addition to the person who is tested. The possibility of genetic discrimination in employment or insurance is also a concern.

Genetic testing can provide only limited information about an inherited condition. The test often can't determine if a person will show symptoms of a disorder, how severe the symptoms will be, or whether the disorder will progress over time. Another major limitation is the lack of treatment strategies for many genetic disorders once they are diagnosed.

A genetics professional can explain in detail the benefits, risks, and limitations of a particular test. It is important that any person who is considering genetic testing understand and weigh these factors before making a decision.

Many people are also concerned about the privacy implications of genetic testimony. In the United States, federal law requires that this kind of medical information to be kept confidential. Violators will often be fined, but charges may be as serious as the death penalty.

[edit] Testing

Diseases and conditions for which testing is available (among the 1300+ tests[1]) include Cystic Fibrosis, Down's syndrome, Huntingtons Disease, Hypertrophic cardiomyopathy, Phenylketonuria, Sickle-cell trait and Tay-Sachs disease.





Gel electrophoresis is the separation of deoxyribonucleic acid, ribonucleic acid, and protein through an electric charge. It is usually performed for analytical purposes, but may be used as a preparative technique to partially purify molecules prior to use of other methods such as mass spectrometry, PCR, cloning, DNA sequencing, or immuno-blotting for further characterization.
Contents
[hide]

* 1 Separation
* 2 Visualization
* 3 Applications
o 3.1 Nucleic acids
o 3.2 Proteins
* 4 History
* 5 See also
* 6 References
* 7 External links

[edit] Separation

"Gel", refers to the matrix used to separate the molecules. In most cases the gel is a crosslinked polymer whose composition and porosity is chosen based on the weight and composition of the target of the analysis. When separating proteins or small nucleic acids (DNA, RNA, or oligonucleotides) the gel is usually made with different concentrations of acrylamide and a cross-linker, producing different sized mesh networks of polyacrylamide. When separating larger nucleic acids (greater than a few hundred bases), the preferred matrix is purified agarose (a component of agar which is a red seaweed extract). In both cases, the gel forms a solid but porous matrix that looks and feels like clear Jell-O. Acrylamide, in contrast to polyacrylamide, is a neurotoxin and needs to be handled using Good Laboratory Practices (GLP) to avoid poisoning.

"Electrophoresis", refers to the electromotive force (EMF) that is used to push or pull the molecules through the gel matrix; by placing the molecules in wells in the gel and applying an electric current, the molecules will move through the matrix at different rates, towards the anode if negatively charged or towards the cathode if positively charged (note that gel electrophoresis operates as an electrolytic cell; the anode is positive and the cathode is negative).

[edit] Visualization

After the electrophoresis runs, when the smallest molecules have almost reached the anode, the molecules in the gel can be stained to make them visible. Ethidium bromide, silver, or coomassie blue dye can be used. Other methods can also be used to visualize the separation of the mixture's components on the gel. If the analyte molecules fluoresce under ultraviolet light, a photograph can be taken of the gel under ultraviolet light. If the molecules to be separated contain radioactive atoms, an autoradiogram can be recorded of the gel (as in the example shown here).

If several mixtures have initially been injected next to each other, they will run parallel in individual lanes. Depending on the number of different molecules, each lane shows separation of the components from the original mixture as one or more distinct bands, one band per component. Incomplete separation of the components can lead to overlapping bands, or to indistinguishable smears representing multiple unresolved components.

Bands in different lanes that end up at the same distance from the top contain molecules that passed through the gel with the same speed, which usually means they are approximately the same size. There are special markers available - ladders - which contain a mixture of molecules of known sizes. If such a marker was run on one lane in the gel parallel to the unknown samples, the bands observed can be compared to those of the unknown in order to determine their size. The distance a band travels is approximately inversely proportional to the logarithm of the size of the molecule.

[edit] Applications

Gel electrophoresis is used in forensics, molecular biology, genetics, microbiology and biochemistry. The results can be analyzed quantitatively by visualizing the gel with UV light and a gel imaging device. The image is recorded with a computer operated camera, and the intensity of the band or spot of interest is measured and compared against standard or markers loaded on the same gel. The measurement and analysis are mostly done with specialized software.

[edit] Nucleic acids

In the case of nucleic acids, the direction of migration, from negative to positive electrodes, is due to the natural negative charge carried on their sugar-phosphate backbone. Double-stranded DNA fragments naturally behave as long rods, so their migration through the gel is relative to their radius of gyration, or, for non-cyclic fragments, roughly size. Single-stranded DNA or RNA tend to fold up into molecules with complex shapes and migrate through the gel in a complicated manner based on their tertiary structure. Therefore, agents that disrupt the hydrogen bonds, such as sodium hydroxide or formamide, are used to denature the nucleic acids and cause them to behave as long rods again.

Gel electrophoresis of large DNA or RNA is usually done by agarose gel electrophoresis. See the "Chain termination method" page for an example of a polyacrylamide DNA sequencing gel.

[edit] Proteins

Proteins, on the other hand, can have different charges and complex shapes, therefore they may not migrate into the gel at similar rates, or at all, when placing a negative to positive EMF on the sample. Proteins therefore, are usually denatured in the presence of a detergent such as sodium dodecyl sulfate/sodium dodecyl phosphate (SDS/SDP) that coats the proteins with a negative charge. Generally, the amount of SDS bound is relative to the size of the protein (usually 1.4g SDS per gram of protein), so that the resulting denatured proteins have an overall negative charge, and all the proteins have a similar charge to mass ratio. Since denatured proteins act like long rods instead of having a complex tertiary shape, the rate at which the resulting SDS coated proteins migrate in the gel is relative only to its size and not its charge or shape.

Proteins are usually analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), by native gel electrophoresis, by quantitative preparative native continuous polyacrylamide gel electrophoresis (QPNC-PAGE), or by 2-D electrophoresis.

Answer 2

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Answer 3

Genetic testing is finding the genes in our DNA. They determine everything about us and these tests can tell much about us from exactly who we are, where we come from or if we will get certain diseases.

Gel Electrophoresis is when you cut up the long strings of DNA to small pieces and use electricity to separate these pieces into a pattern in order to read a genetic test.

Genetic tests can be done in many other ways but gel electrophoresis is the way it is done for evidence in court or legal trials because it has proved less prone to error.

Answer 4

Electrophoresis is the separation of particles caused by an electric current. Scientists use this process to examine the human body and other species at the genetic level. The process separates components of DNA to determine the presence of certain genetic makers and even the presence of disorders and diseases. The relative low cost and extreme accuracy of the testing has enabled science to map genetic markers for a variety of blood-borne disorders, including sickle cell anemia...

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Answer 6

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