How Accurate Is Genetic Paternity Testing?

Paternity test refers to the identification of the biological relationship between the accused parents and children based on the genetic laws of hereditary traits between offspring and parents using biology, genetics and related theories and techniques. The cases involved include: support disputes for children born out of wedlock, disputes over inheritance of property, identification of biological children caused by misadjusted newborns in the delivery room of the hospital, and claims for abducted and separated children. Paternity testing is mainly based on the genetic laws of human blood types and simple genetic traits other than blood types. The genetic traits are controlled by genes located on chromosomes in the nucleus of the cell. Offspring. Gene delivery follows a certain pattern. (1) The offspring genes are from the parents, half from the father and half from the mother. (2) The offspring will not have the gene unless one (or both) of the parents has the gene. (3) If one parent is homozygous for the gene, all offspring carry the gene. The most commonly used method in paternity testing is blood group testing. All blood group systems (erythrocyte blood group, white blood cell blood group, serotype, red blood cell enzyme type) are passed from parent to offspring according to Mendelian genetic laws, and can be used as parental identification Basis. However, the result of blood group identification can only be used as a basis for negating the biological relationship. Although the non-parent exclusion rate and the probability of affirming fatherhood can reach more than 99%, it cannot be 100% sure. The identification of genetic traits other than blood type, such as fingerprints, earwax type, PTC taste blindness, appearance characteristics, and duration of pregnancy, fertility, etc. can only be used as a reference for paternity testing. The development of modern biotechnology has been able to obtain DNA fingerprints by hybridizing molecules of DNA fragments. Such technology can be used to reduce the probability of randomization to one in 30 billion by applying paternity tests. ^[1]

Paternity test is a typical application of genetic statistics theory in forensic science. Paternity test is based on genotyping information of genetic markers of parents and offspring (such as STR loci). It is a method of inferring whether there is a genetic relationship between the father and the child through the likelihood ratio test in statistics. The statistical indicators commonly used in paternity testing are paternity index and average non-paternal exclusion rate. In the paternity test report, these two indicators are generally reported at the same time in order to comprehensively evaluate the test results ^[2]

The main reason for paternity testing: With the development of science and technology and the change of traditional family concepts, the level and demand of modern biotechnology coincide. Because of liberalization and people's openness to gender relations, ethical contempt, and changes in life style, many couples worry that their children are not their own after marriage. Most of them are husbands who suspect that their children are not biological, and that they have more than one child Women who have had sexual relations, in order to find out who the child's biological father is, they propose pregnancy.

Genetic theory has confirmed that half of each child's genomic DNA comes from the biological parent. The relationship identification conducted by the forensic medical evidence profession includes the following categories:

1. Routine biological blood relationship identification: This is the type of parental relationship identification with the greatest demand, including parent and child three parties (also known as triads), father and child (or mother and child) both parties (also known as duplexes). . The accuracy of this type of identification can reach 99.999999%.

2. Intergenerational kinship identification: This type of identification refers to confirming the kinship between great-grandparents, grandparents, and great-grandchildren (great-granddaughters) and grandchildren (granddaughters). It also includes simple paternal relationship identification to confirm the kinship between great-grandfather, grandfather, great-grandson, and grandson, and simple maternal relationship identification to confirm the kinship between great-grandmother, grandmother, and granddaughter .

3 Difficult kinship identification: In addition to the above two categories, there are some more difficult kinship identifications, such as identification of siblings (brothers, siblings, sisters, sisters), cousins, and uncles Identification of kinship between aunt, niece and niece, and niece (nephew).

The theoretical basis for judging the biological relationship is Mendel's genetic separation law. According to this rule, when gamete cells are formed, the paired alleles are separated from each other and enter the respective gamete cells. Sperm and egg cells fertilize to form offspring. The two genomes of the child are one from the mother and one from the father; therefore the alleles of the same pair are one from the mother and one from the father. If the identification result meets this rule, the biological relationship is not excluded, if it does not, the biological relationship is excluded (except for the variation). In most cases, the mother-child relationship is known, and the identification requires a hypothetical parent-child relationship. At this time, from the comparison of maternal and child genotypes, it is possible to determine the genes in the child's genes that may be derived from the father (born father gene, OG). Then observe the genotype of the hypothetical father. If you do not have the biological father gene, you can exclude the hypothetical father-child biological relationship. If it is assumed that the father also has the biological father gene, the result cannot be assumed to assume the biological relationship of the father. Assume that in a case the mother is FGA-22 / 23 and the child is 22/25. From the comparison, the biological father gene is FGA-25. In this case, it is assumed that Father 1 is FGA-22 / 24; Father 2 is 24/25. Among them, it is assumed that Father 1 does not have the biological father gene 25, so he can exclude the biological relationship between him and his child; in contrast, assume that Father 2 has FGA-25, which does not exclude the biological relationship with the child.

The steps of DNA paternity test are as follows:

Step 1: DNA extraction

The DNA contained in the nucleus of the sample is extracted and then purified to remove impurities from the sample.

Step 2: PCR amplification

The Chinese name of PCR is polymerase chain reaction. To put it simply, the step of PCR amplification is to make a large number of copies of the fragments we need through an enzymatic reaction on a PCR instrument, and enlarge it to be seen by some special instruments. Degree.

Step 3: Post-PCR reaction

This step is mainly on the preparation stage of the ABI sequencer. The double-stranded DNA is opened, and some internal standards for detection are added, which are mainly used to mark the length of the detected fragments.

Step 4: Capillary Sequencer Detection

Due to the charge of DNA, the electrophoresis speed of different fragments of DNA is different by capillary electrophoresis. At the same voltage and the same electrophoresis time, the swimming distance is different. These different lengths can be measured by the internal standard added earlier. It can be distinguished and displayed on the computer at the same time by a certain software, which is convenient for inspectors to process and analyze the data.

Step 5: Analyze the data and issue a report

The main purpose is that the tester analyzes, summarizes, and calculates the results, and then draws out conclusions and reports.

Shanghai family paternity test is a very serious matter, and it is also a paternity test derived from China s unique hukou management system. It is widely used in the field of paternity test. In the 2010 census, due to preferential measures for Shanghai hukou Set off a paternity test fever.

I. The paternity test needs to be done before the household registration:

1. No birth certificate. For various reasons, the child was not born in a hospital with a maternity and obstetrics qualification, or was not born in a hospital, so there is no standardized birth certificate, and a paternity test is required when entering the household registration. Or you have a birth certificate, but the parent s name on the birth certificate is inconsistent with the name on the household registration book. A paternity test certificate is required.

2. Because the child was trafficked, lost, and later retrieved through various channels, the hukou needs to be brought up with the biological parents, and a paternity test report certificate is required.

3. Unmarried birth, the existing legal documents cannot prove the child's biological parental relationship. Or single-parent families, the child's household registration needs to be transferred from the father's side to the mother's side, or from the mother's side to the father's side, to do a paternity test.

4, abandoned children go home. If the child is being adopted and adopted, or because of avoiding family planning, the child's account must be transferred to the name of the biological parent under the name of another person, and a paternity test must be performed.

5. Special regulations of the department, because some departments are afraid of other industries to enter special industries when recruiting and recruiting, parents and children of this industry need to prove their parent-child relationship when recruiting. For example, the Zhengzhou railway system requires a paternity test certificate to recruit workers.

6. If the adopted child comes to the household, it is necessary to prove that the child and the adoptive parent are not in a biological relationship.

2. The procedures required for the parent-child identification of the household: The parent-child identification of the household is a process of self-evidence by the person in charge of the household. Therefore, the identification certificate only needs to be provided by the party concerned:

1. Certificates that can prove the identity of the person being identified: such as ID card, household registration book, military identity certificate, birth certificate, etc. Those without the above certificates need to apply for appraisal certificates from the people's governments at or above the township level, street offices, and police stations.

2. The appraised person must go to the judicial appraisal center to collect blood to participate in the appraisal and complete the identity verification work. Mainly verify the identity certificate, fingerprints and photos.

3. If it is really inconvenient for the appraiser to sample at the judicial appraisal center, etc., you can contact the staff of the judicial appraisal center to sample and verify the identity.

Third, select the identification agency. There are many agencies for paternity tests, but the household paternity test belongs to the category of judicial appraisal. Therefore, when selecting an appraisal agency, you must have "". The paternity test report must be valid nationally and recognized by the national public security and judicial departments. At the same time, internationally recognized judicial appraisal agencies are required to do the appraisal (such as kidnapping of children to foreign countries or Hong Kong).

4. Parent-child appraisal of people in the households: Only considering the needs of the households, it can be a father-son (female) or mother-child (female) appraisal. But due to paternity test

It is assumed that the ratio of the probability that the father provides the biological father gene to become the child's biological father to the probability that the random man provides the biological father gene to become the child's biological father is called the paternity index (PI). The former possibility is assumed to be X; the latter possibility is assumed to be Y. The above example assumes that the father 2 genotype is 24/25 heterozygotes. The probability that he will provide the biological father gene FGA-25 is 1/2, that is, X = 1/2. The chance that a random man provides the biological father gene FGA-25 is the frequency of the gene, that is, Y = 0.0958. Therefore, the PI value in this example is 0.5 / 0.0958 = 5.22. If it is assumed that Father 2 is indeed the child's biological father, no matter how many sites are detected, the biological relationship between him and the child will not be excluded. At all the detected sites, one PI value can be calculated for each site. The cumulative PI value of a point is equal to the product of the PI value of each point, but the prerequisite is that there is no genetic linkage relationship between the detected points.

The triplet genotype combination can be summarized into three principles:

(1) When the father is assumed to be homozygous, X = 1; when the father is assumed to be heterozygous, X = 1/2, but when the heterozygote assumes that both genes of the father may be biological father genes, X = 1.

(2) When only one biological father gene is involved, the Y value is equal to the frequency of the biological father gene.

(3) If two biological father genes are involved, the Y value is the sum of the frequencies of the two biological father genes.

1. What is a DNA paternity test?

DNA (

I. Bloodstain Sample Collection Method :

1. Prepare alcohol cotton balls, blood collection needles, medical sterilized gauze, and paper envelopes before blood collection.

2. When taking blood, first sterilize the blood collection site with an alcohol cotton ball, and sterilize the blood collection needle. Take five drops of thumb-sized blood and drop it on the medical yarn.

Cloth.

3. The blood of adults and children is dripped on different gauze, and marks (parents and children) are recorded to record the date of collection.

Precautions:

1. Blood stains can be taken from ear margin blood or fingertip blood, and infants can collect heel blood.

2. Bloodstains should be allowed to dry naturally in the shade on the tabletop, and should not be heated or exposed to the sun.

3. The blood samples of different people cannot be in contact with each other. Put them in different kraft paper envelopes, and the envelopes are clearly marked.

Methods of nail collection

Sampling method:

1. Before the sample is collected, the person providing the sample must first remove the dirt in each nail (such as a toothpick, etc.), then wash the hands with water and dry the hands with disposable paper towels or disposable gauze;

2. The sampling staff should also wash their hands and wear gloves before sampling;

3. Use nail clippers or scissors (wash with water or alcohol before each use to avoid the DNA content of the former) to remove the free edge of the nail, and then put it on the white paper prepared in advance;

4. The closer to the inside (near the finger meat) when cutting nails, the better it is. After cutting, wrap them in clean white paper (do not use plastic bags to seal). At least 3 nails are required;

Precautions:

1. When collecting samples, do not touch the nails directly with skin other than the provided samples;

2. Put it in a paper envelope after it has dried naturally. Do not use plastic wrap or plastic bags to prevent mildew from affecting the quality of the test.

3. After sample extraction is completed, please send it to our company as soon as possible. If you need to store it, please store it in a dry, low temperature and dark place.

Methods and requirements for collecting cigarette butts

1. Collect 2-3 cigarette butts (after removing the ashes) from the appraiser;

2. Pack the cigarette butts into a paper envelope bag after collection (not sealed with a plastic bag) and mark them.

Precautions:

1. Make sure the collected cigarette butts have been consumed by the same appraiser;

2. Try to avoid touching the part of the cigarette butt when collecting samples;

3. After sample extraction is completed, please send (mail) to this identification center as soon as possible to avoid degradation of DNA due to environmental factors and affecting test results.

Extraction of amniotic fluid samples

special reminder!

What is the difference between a legal use test and a personal test?

The methods and accuracy of the legal appraisal and private appraisal are exactly the same. The only difference is that legal appraisal requires the subject to provide fingerprints, photos, and identification, and the sample sampling process needs to be performed by a legitimate witness. Private identification does not need to provide photos or fingerprints, and the entire sampling process can be carried out by itself, completely confidential. Therefore, the DNA identification results of the private collection of specimens have no legal effect.

Can a paternity test be performed without the birth of a mother?

The birth mother may choose not to participate in the identification. In paternity tests, samples from children and hypothetical fathers are usually sufficient to know the results, and mothers may choose not to participate in the tests. The biological mother also tested and the conclusion was more accurate. Because the child's genes come from the mother and one from the father. If a biological mother is used as a reference (ie, parent identification), the gene of the biological father can be more clearly derived based on the genotypes of the mother and child, so as to compare it with the disputed parent (that is, you). If there is no mother, the biological gene of the father is derived directly from the child's gene. There are many possible situations, and the final statistical value is relatively large.

In fact, we commonly used the results of testing 15 STR loci for computer simulation of a single parent case. Two unrelated people, using this detection system, at least 3 violated the genetic laws, 99.99% of non-parents. Can be excluded, but there may be 1/1000 that cannot be ruled out and mistakenly identified. Therefore, the difference between single parent identification and other organizations is that we also add a kit and add 9 detection indicators, which is more accurate and avoids deviations as much as possible. This is why the cost of single parent identification is higher than that of the biological mother involved in the identification.

Do paternity tests need to be present?

Paternity tests can be divided into two types. One is the need for judicial effect, such as lawsuits, immigration, and household registration. The other is just to understand the results and does not involve judicial purposes. For the former, it is only necessary to provide identification information of the parties, parents provide ID cards, and children can provide birth certificates or household registration certificates to prove the identity (the client is the guardian of the child). If you have entered judicial procedures or have hired a lawyer, the judge or lawyer may commission an evaluation. It can also be entrusted jointly or unilaterally by both parties. For the second type, there is no need to provide any information, it can be anonymous, and you can bring your own samples. The two types of fees, identification methods, and evaluation standards are exactly the same, but the differences in procedures, that is, legally valid judicial identification certificates, require us to review the identity card of the party and take a picture.

Will a paternity test cause harm to pregnant women and the fetus?

The forensic center of the appraisal center said that there is no need to worry because the technology is very mature. Whether it is to take villi or amniotic fluid samples, it is the same as the prenatal diagnosis of the fetus, which basically will not cause any harm. Fetal paternity testing is performed by extracting villi or amniotic fluid from pregnant women. To ensure safety, pregnant women are recommended to choose a top three maternity hospital for sampling. The technologies in the relevant aspects of the top three maternity hospitals are mature and will not harm the fetus and pregnant women.

The appraisal center has a special car pick-up service and staff to accompany customers for sampling services on fetal paternity tests. Amniotic fluid extraction is also performed by a professional top three doctor under the B ultrasound, which is safe and reliable. And the appraisal center has accepted tens of thousands of cases of fetal (prenatal) appraisal commissioned nationwide, and has rich appraisal experience.

What circumstances need to do immigration paternity test?

1. The child's parent is a non-Chinese nationality, the child was born in China, and the household registration relationship needs to be transferred abroad.

2. Both parents of the child are foreign nationals. The child was born in China, and the child will settle abroad with the parents.

3. Foreign nationals who have immediate family members in China need to settle abroad;

4. Chinese nationals who settle abroad, children's relocation, etc .;

Fetal paternity test refers to the use of genetic technology to identify the father in the genetic sense of the fetus. When the father in the genetic sense of the fetus is unknown, the "antenatal paternity test" can extract cells from the amniotic fluid of a pregnant woman and confirm the father-son relationship by identifying the fetal DNA (DNA). The paternity test can be used to detect fetal DNA through villus biopsy and amniotic fluid identification from the fetal stage. After 10 weeks of pregnancy, villous puncture surgery can be performed, and after 16 weeks of pregnancy, amniotic fluid can be tested. This article describes the method of paternal paternity testing.

One.

When we plan to do a paternity test, our mental state is most important at this time.

In most people's opinion, the most straightforward way of paternity test is to test whether the spouse (to be exact, the wife) is loyal. Men are not afraid of suffering, tiredness or even sacrifice. However, wearing a "green hat" is one of the most taboo and shameful things for men ...
The husband suspected that his wife had a "third party", and even coaxed and cheated to take the child for a "medical examination", but the paternity test was done on the back; the young girl deliberately let herself "accidentally" get pregnant in order to save money, He also took paternity tests as a threat, and was particularly happy to be a "second wife" ... I don't know when, paternity tests seem to become "patents" for digging "third parties" and "sugar daddy".
"In fact, this is a misunderstanding. Paternity tests have extraordinary social significance in terms of disasters, such as finding a dead body (such as an earthquake), looking for abducted children, and helping raped women find evidence for suspects." For example, previously The raped woman must find the evidence and wait until the child is born. This is undoubtedly an unbearable pain for the victimized woman. Through fetal DNA

Genetic theory has confirmed that half of each child's genomic DNA comes from the biological parent. The relationship identification conducted by the forensic medical evidence profession includes the following categories:
1. Routine biological blood relationship identification: This is the type of parental relationship identification with the greatest demand, including parent and child three parties (also known as triads), father and child (or mother and child) both parties (also known as duplexes). . The accuracy of this type of identification can reach 99.999999%.
2. Intergenerational kinship identification: This type of identification refers to confirming the kinship between great-grandparents, grandparents, and great-grandchildren (great-granddaughters) and grandchildren (granddaughters). It also includes simple paternal relationship identification to confirm the kinship between great-grandfather, grandfather, great-grandson, and grandson, and simple maternal relationship identification to confirm the kinship between great-grandmother, grandmother, and granddaughter .
3 Difficult kinship identification: In addition to the above two categories, there are some more difficult kinship identifications, such as identification of siblings (brothers, siblings, sisters, sisters), cousins, and uncles Identification of kinship between her, her aunt and her nephew, and between her and her nephew (nephew) ^[1] .