DNA Testing Information and Resources » DNA Testing Basics

Sibling Testing

admin — Thu, 30 Dec 2010 01:11:48 +0000

Sibling DNA testing is used to determine whether the two people in question share the same biological parents, especially when those parents are not available for testing. Sibling testing can determine if the test subjects are full siblings or half siblings.

Full siblings are individuals who are born of both biological parents. Half siblings share only one biological parent, either the mother or the father.

Sibling analysis is not as conclusive as paternity testing. The results will provide a statistical likelihood of whether two individuals are true biological relatives, but sibling analysis cannot provide a conclusive result. The statistical likelihood in this case is expressed as a likelihood ratio. The likelihood ratio summarizes the information generated from the DNA test. A likelihood ratio of LESS than one means that the test subjects are unlikely to be related. A likelihood ratio GREATER than one means it is likely that the test subjects are related. (The range is from one to infinity)

If any of the parents of the siblings who are being assessed are available for testing, this will increase the certainty of the result. As in a paternity test a DNA profile is produced for each person made up of a number of DNA markers. The DNA profiles of the two people are then compared.

On average full siblings will share more DNA markers than half siblings, and half siblings share more DNA markers than unrelated people. The statistical analysis performed will determine the most likely relationship given the DNA results.

There are different variations of sibling testing.

BROTHERS Y-TEST

This is premised on the fact that all men have one Y chromosome which they pass to all their sons. By testing this Y chromsome in two or more brothers, we can see if they have the same father. The results of sibling testing for males is 99.9%.

SISTERS X-TEST

The basis of this test stems from the fact that all men have one X chromosome which they pass to all their daughters. By testing the X chromosome in two sisters, it is possible to detect if the test subjects have the same father. This test is best carried out for sisters with different mothers.

MITOCHONDRIAL TEST

Mitochondrial DNA is only inherited from the mother, so it is the ideal test to see if siblings have the same biological mother. The accuracy of the test is highly dependent on the type of mitochondrial DNA you have. If two matching persons have a rare type of Mitochondrial DNA then they are more likely to be siblings, than two persons who match with a common type of mitochondrial DNA.

The full sibling test is required to test a brother and sister for the same father.

Hair Paternity Testing

admin — Thu, 23 Dec 2010 01:09:04 +0000

Testing of samples of the hair has become an important tool in paternity DNA testing. In many cases where the paternity of an unborn child is in question, it is not uncommon to see many alleged fathers refusing to submit themselves for testing using the conventional buccal swab technique. Since consent must be sought from all parties before medical procedures are carried out, hair paternity testing has become one of the so-called “discreet/forensic testing” methods. This is also important when pregnancy has resulted from sexual abuse or sexual assault, and in cases of retroactive testing when the subjects are dead or missing.

Hair paternity testing can therefore be defined as the process of determining the paternity of an unborn child using hair samples from the alleged father, while using other conventionally collected samples from the mother and foetus.

In all cases, hair samples used for hair paternity testing must be complete with the hair follicle or root attached so as to obtain a more complete DNA profile. Cut hair does not have a significant amount of DNA.

Many murder and rape cases have been solved by using hair paternity testing, especially if there was a struggle and the hair of the assailant was pulled on and got lodged in the woman’s nails.

Generally, 6-10 strands of hair are required to build a complete DNA profile for a hair paternity DNA test. Hair paternity test results are usually admissible in court if a legal battle ensues.

Pre Paternity Test – Best Way To Determine The Identity Of The Father

admin — Mon, 29 Nov 2010 00:57:09 +0000

Under certain circumstances it becomes necessary to do pre-paternity testing to determine the father of the child. These tests are available, but are not available as home testing kits. Pre-paternity testing has to be carried out by a trained physician.

While it may be necessary for the mother to want or need to know the identity of the father of the child, the life and health of the unborn fetus is of utmost importance to the doctor. The procedures that are available for pre-paternity testing are sometimes slightly invasive when taking some of the DNA in order to determine the identity of the father. Although the test is not harmful to the baby in most cases, it does involve the fetus being disturbed, and there are certain factors that need to be considered.

When considering pre-paternity testing, it is very important that the doctor examine the mother to see how far she is into the pregnancy in order to determine what type of re-natal paternity testing can be carried out. The doctor will also check the health of both the baby and the mother, to determine whether complications are a possibility or not. If the doctor has any doubts whatsoever, he/she will recommend that the pre-paternity testing be carried out after the birth of the baby.

There are two extraction methods that the doctor can carry out in order to obtain the DNA necessary for the test. The first method is CVS, or chorionic villi sampling, that can be performed during the tenth and thirteenth weeks of pregnancy. A sample of the placenta can be obtained either through the vagina or the abdominal area. This will give conclusive identity of the father, as the material that makes up the placenta has exactly the same DNA as the original egg cell.

Between the fourteenth and twenty-fourth weeks of pregnancy, an amniocentesis test can be carried out. A needle is inserted into the amniotic sac and a small amount of the fluid extracted. As this test is done directly into where the fetus is developing, there are risks involved, although complications from this test are very rare.

Although both methods pose a risk for the mother and the baby, both are safe in most cases. There is always concern that the needle may injure the baby during the amniocentesis test, but because doctors are now well trained in this method, the risks are a lot less than when the procedure was first introduced. Bleeding and cramping could also occur with both of these methods, however, staying in contact with the doctor will ensure that nothing goes wrong.

Due to the invasiveness of both procedures, and laboratory fees involved with extracting the DNA from the samples, pre-paternity testing is expensive. If an amniocentesis test is done to determine the health of the baby, there are some insurance companies that will cover this test, although not for paternity testing.

Paternity Test Before Birth

admin — Tue, 23 Mar 2010 11:55:05 +0000

With the rising numbers of children growing up without or not knowing their own fathers, there is a great need for a paternity test before birth. Often times, men deny that they have fathered the child, and women often do not know how to prove it. Thanks to advancements in medicine, these pre-natal paternity tests are readily available.

How Are These Tests Administered?

There are actually two ways to go about these tests. Both tests involve minor surgery that involves minimal risks. These tests have the ability to determine who the father is, through DNA testing. These test can also determine if the child is normal or not, which allows parents to prepare for the future.

Here are those methods:

Chorionic Villus Sampling (CVS)

This test can be administered 10 to 13 weeks after the woman’s last period. This test involves invasive surgery to both mother and child, since the child is still inside the womb. A sample of the placental tissue or CVS is gathered for DNA testing.

Amniocentesis

This test can be administered 14 to 16 weeks after the woman’s last period. This test involves inserting a needle into the mother that collects amniotic fluid. This fluid is found in the amniotic sac, which surrounds the developing fetus. This fluid contains fetal tissue that contains the baby’s DNA.

What Are The Risks?

There are a few risks that a paternity test before birth has that you should know about. Just like any medical procedure, there are risks involved. These risks include cramping, bleeding, and harm to the child inside the womb. This is why you should make sure that a trained and reputable professional is administering the procedure.

What Is The Purpose Of These Tests

There are a growing number of children abandoned by their fathers even before they are born. This leaves the mothers no choice, but to shoulder the financial support that was supposed to be shouldered by both parents. To avoid this from happening, the test determines who the father is. This prevents the father from denying the unborn child his responsibilities.

Initially, these tests were administered to determine through DNA testing, if the unborn child have any genetic abnormalities. In some cases, the pregnancy poses risks to both mother and child. A paternity test before birth enables the parents to take the necessary action to ensure both the child and mother’s safety.

What Are The Advantages?

Before these men can run away from their responsibilities, a paternity test before birth will enable the woman to take legal action, and get the child support that she needs. This prevents the possibility of financial strain to the expectant mother, and ensures a better future for the unborn child. This also lessens the stress of the expectant mother. We all know how stress can affect the development of the unborn child.

In any case, these tests will make sure that mother and child are in perfect health. A paternity test before birth also ensures that a father does not run away from his responsibilities.

DNA Testing

admin — Sun, 27 Dec 2009 00:40:03 +0000

What is DNA testing?

Deoxyribonucleic Acid is the genetic material in most of the living beings on planet world. Each individual has a unique set of DNA which is also a characteristic or profile of that individual. In forensic science the need for identifying a person through his genetic basis aroused when no other clue was left which could give proper details related to that person. Based on this requirement of the forensic sciences a technique called DNA testing was developed in which a person is identified by the patterns of his or her DNA. As no two individuals can ever have the same DNA this technique proved great help in solving many crucial cases and also led to many important discoveries.

The other names that have been given to this technique of DNA testing are DNA profiling, DNA typing and also Genetic fingerprinting. All of these terms indicate the same technique and methodologies. Since this technique is based on the DNA profiles it is important to know what DNA profiles are to understand the mechanism of this technique. The entire DNA Built of an individual is in the set of an encrypted language this is termed as DNA profiles. These DNA profiles are the genetic identity of a person and this is the code which differentiates us from the rest of the world.

In the human body only a 0.1% of the DNA is different from the other person. Almost 99.9% of the DNA is alike in all the humans. But this mere difference of 0.1% makes every individual dissimilar. For this technique of DNA testing VNTR’s are used. VNTR are Variable number tandem repeats. These are the DNA profiles which are variable and repetitive in the entire DNA of the person. The loci of VNTR can never be similar in two unrelated people. All this basic information is used for DNA testing of a person.

How it is done?

The course of action for DNA testing of a person is initiated by simply taking the sample of DNA of a person. Buccal swab is used for collecting DNA sample so that the reference sample does not gets contaminated any how. The DNA of another person (Supposed to be his relative) is also taken so that later comparisons can be made whether the person examined is linked to that person or not. After collecting the reference samples techniques like PCR, RFLP analysis, STR analysis are used for making a DNA profile of that person.

RFLP analysis: This was the most primitive method for profiling a person’s DNA which made use of restriction enzymes and then later the technique of southern blotting. This technique was overall very arduous and this is why it was later reinstated with PCR assays.

PCR analysis: The discovery of this method for DNA testing greatly reduced the complexity of the entire procedure and also improved the final outcome. PCR is polymerase chain reaction and in this technique the DNA of the person is amplified greatly which results in the examination of a small part of the DNA perfectly. This method is also sympathetic for identifying the loci of VNTR.

STR analysis: in this method short tandem repeats are used for profiling a person’s DNA using the polymerase chain reactions. Since every individual has different STR’s therefore the identification of STR loci becomes easy through this method.

History of DNA testing

Two breakthroughs in the medical technology ultimately led to the discovery of this highly important and useful technique of DNA testing. Sir Allec Jeffery in the year 1984 discovered the technique of DNA fingerprinting in England and simultaneously in United States of America Kary Mullis developed the technique of polymerase chain reaction. Both of these discoveries were made individually but when the two techniques were used together it resulted out in the invention of the ultimate modus operandi of DNA testing.

In 1986 Sir Jeffreys used DNA for investigating a criminal. Samples which were stained in semen were used for DNA fingerprinting. The final result of this investigation was worth the time invested in this procedure. This is how this entire technique popularized and ultimately gave rise to better techniques like DNA testing.

Types and purpose of DNA testing

Two major types of DNA testing are available up till now. These are:

Mitochondrial DNA Testing
Y Chromosome Testing

Through the technique of mitochondrial DNA testing the maternity history of a person can be found out. In this the three regions coding region, HVR2 and HVR1 are tested. A hyper variable region signifies for the areas where more VNTR are available.

Y Chromosome DNA testing is used to the paternal history of a person. Y chromosome decodes the information that is only passed to a son from his father in the form of his Y chromosome.

The purpose of DNA testing is found majorly in identifying the suspects of a crime. DNA testing is mostly used in the forensic science for solving a case. The links between two people are identified through their DNA genetic basis. This technique has helped in solving many cases. In cases of murder, rape and accidents DNA testing technique is of great use because it helps in solving the case with great ease. A culprit can never runaway from his own DNA information. The DNA helps in getting that criminal caught which ultimately leads to a solution.

This is why DNA testing is regarded to be a major discovery in the world of forensic science. It is simplified the way cases were solved. This technique has also helped scientists in making the DNA genome of a person and also in coding and decoding the various bases and base pairs in a DNA. New techniques are added from time to time for updating this method of DNA testing and for making it more reliable and accurate. DNA testing is therefore a great tool for the world of forensic science as no culprit can run away from them now.