+353 (1) 685 6929 Sibling DNA testing is a means of determining what the nature of the relationship between siblings is. Siblings can have both parents in common, meaning they are full siblings; one parent in common, which would make them half siblings or perhaps no parents in common would mean they are not siblings at all.
Sibling DNA: How much DNA do they really share?
It is hard to provide an accurate percentage of shared DNA that applies to siblings; however, it is estimated that full sibling (which share both biological parents) will share around 50% of their DNA. There may be instances where full siblings share very little of their DNA or some cases in which they may have 100% of their DNA in common- the latter example is only seen however, with identical twins.
Sibling testing falls under the umbrella of relationship DNA testing. Relationship tests are designed so as to solve diverse familial relationships involving aunts, grandparents, cousins and of course siblings.
The proximity of the genetic relationship between full siblings makes sibling testing quite accurate.
With cousins, for example, things are more complicated should they wish to establish whether they are truly cousins- first cousins only share around 25% of their genetic makeup and this number falls by 1/5 with each successive generation. Half siblings will also share around 25% of their DNA.
How is a sibling DNA test done?
Sibling DNA tests are normally carried out by means of a simple mouth swab which is rubbed inside the mouth to collect cheek cells and saliva. The test is normally used to determine whether siblings share a common parent- usually the father. Since the accuracy of the test is not as high as a paternity DNA test, the first option to consider for any siblings wishing to know whether they have a common father is to do a paternity test- hence, testing directly the alleged father’s DNA sample and comparing this to the DNA of his children. However, in some cases, the father may not be available for testing and is such cases it is worth doing sibling testing.
Because sibling DNA testing involves establishing a biological relationship with another person without testing their DNA makes this test, as mentioned above, less accurate.