Home > News > Testing Guide >

What is DNA? PART 2: HUMAN DNA & HOW IT IDENTIFIES US

FAQS
  • What is the age limit for DNA tests?

    There is no age limit on DNA tests. A DNA test can be performed on an individual at any age.
  • What is a buccal swab?

    Buccal swabbing is a non-invasive way to collect DNA samples from the cells of a person's inner cheek. Buccal means cheek or mouth. A buccal swab resembles a large cotton tip. It is used to collect cheek cells by rubbing the inside of the cheeks. A buccal sample is as accurate as a blood sample. Check Sample Accuracy page to learn more.
  • What if the father is not available?

    It is possible to establish paternity even without doing an paternity test. Paternity can in fact be established by testing relative of the alleged father or your sibling. If only the child and relative of alleged father are tested, the results may not be completely conclusive. If the mother's DNA sample is available for the testing, the results will be more conclusive.
  • How long can I get my results?

    Once all the specimens have been received at the lab, results take an average of 3 business days. Rush results are available upon request.
What is DNA? PART 2: HUMAN DNA & HOW IT IDENTIFIES US
Issue Time:2015-10-12

From one person to the next, our DNA is almost identical. What makes us 'unique' at a genetic level is that our genes differ slightly from individual to individual. These variations in a person's genes are called polymorphisms. In human Identification, we are interested in a specific type of polymorphism known as Short Tandem Repeats (STRs).

STRs are short sequences of 2-5 base-pairs that repeat themselves in a single locus. For example, at locus of gene D7S280, the repeat sequence is "GATA" and it may occur six times. In another individual, the repeat sequence may be seen 10 times. This alternative form of a gene is known as an allele and it is expressed as the number of times the repeat sequence occurs.

Continuing our example with gene D7S280, alleles of this gene are found on human chromosome 7 and have between 6-15 tandem repeats of the "GATA" sequence. An example of a sequence with 15 tandem repeats can be seen in the table below. Note that the table below shows the base sequence for only one chromosome. Because we have a pair of chromosomes, there will be another sequence generated for the other gene.

If the genes from both chromosomes have identical alleles (homozygous), the sequences will have an identical number of tandem repeats. Therefore, both alleles are expressed as a single number.

For example:

LOCUS                     ALLELES

D7S280                         15

If the genes from both chromosomes are different alleles (heterozygous), the sequences will have different tandem repeats. Therefore, the alleles will be expressed as two numbers.

For example:

LOCUS                     ALLELES

D7S280                       6   15

DNA Profiles

The FBI has developed a standard set of 13 STR loci to be used for human identification, known as CODIS STRs. At our laboratories, we use up to 26 STR loci for testing, including all 13 CODIS STRs, to generate a DNA profile for every person tested. These loci have the highest degree of polymorphisms and are always used in forensic cases and relationship/paternity testing worldwide.

An example DNA profile in a DNA Profile report for a single individual would look like this:

 

An example of DNA profiles in a paternity test report would look like this:

 


You May Concern:

The Danger Of Unreliable Paternity Tests

No Room For Genetic Errors

DNA Tech Lab (DTL) Paternity Testing Process

What Is Junk DNA And How Does It Affect My Paternity Test?

KeyWords

Don't forget to sign up!

Find out early about all upcoming promotions and new products releases.

Contact Person
Aceprobe Technologies (India) Pvt. Ltd.
leave a message:
Contact Now
Address:
Aceprobe Technologies (India) Pvt. Ltd., Block No. C-2, Plot No. 296, First Floor, Janakpuri, New Delhi, India