Home
Your Body
Nutrition
Health Problems & Therapies
Supplements & Vitamins
Ask a Question

Answer to your Health Question

Question (12/11/2013):

Title: Sibling DNA Results.

We had a dna test done with half brothers and I don't fully understand the results:

It was 74.62% combined half sibling index:2.9 shared alleles:32 of 39

Answer:

Siblingship tests are based on a prior probability of 50%. This means that 50% probability is the starting point and and results that lean towards being positive will raise that probability above 50%.

The probability of the stated outcome is 74.62%.

If the siblingship index is less than 1.00, this indicates non-relatedness. If the siblingship index is greater than 1.00, this indicates that the two tested individuals are more likely to be true full sibling or half siblings.

The genetic data are inconclusive but support a half-sibship relationship.

Combined Half-sibship Index: 2.9
Probability of Half-sibship: 74.62%

However, only those indices in excess of 25 are regarded as conclusive evidence. Therefore, the genetic data
in this case are, strictly speaking, inconclusive but comprise evidence in favor of half-sibship.

Unlike a DNA paternity test which will always provide a conclusive result, sibship tests are different. When a sibship test is conducted, the DNA laboratory will determine the genetic profile of the alleged siblings. Based on the type of genetic material inherited by each sibling, a sibship index is determined. If the sibship index is less than 1.00, this indicates non-relatedness. If the sibship index is greater than 1.00, this indicates that the two tested individuals are more likely to be true biological siblings. The higher the value of the sibship index, the greater is the likelihood that the two individuals are true biological siblings.

Regarding the shared alleles:32 of 39, for more distant familial relationships, allele sharing decreases.

While sibling testing can give a strong indication of probability of a relationship between two people, it is rarely conclusive. This is because although 2 people can share the same parent, they may only share a few of their recognizable DNA markers.

The more markers tested however, the more accurate the results may be. If both people are male, an alternative option includes Y Chromosome DNA Tests. These can conclusively conclude if 2 men share the same father or not.



Do you have any other questions? Enter your health question or go to Medwhat

Disclaimer: The information contained in this web site is for educational purposes only and is not meant to replace medical advice, diagnose or treat any disease.
Your use of this site indicates your agreement to be bound.