Are you curious to learn how much DNA you share with each of your four grandparents? Read this post and gain all the details regarding any shared strands between you and them.
Your DNA relationship to each grandparent and how many segments should be shared between grandparents will also be discussed.
Actual examples of shared DNA between real people and their grandparents
What to Learn From Your Grandparent’s DNA Results
With DNA testing becoming more popular every year, more and more people have been testing to see how much of their genetic material they share with relatives; grandchildren and grandparents are no exception.
If one or more of your grandparents has taken a DNA test, this can be an incredible boon for you! Through their results you’ll gain more information about your ancestry than could ever be gained with just your results alone.
At the end of this post I will explain why. Don’t skip that part!
Let’s begin our DNA exploration by discovering how much of theirs we share and the nature of that shared genetic material.
Does Your DNA Match With Grandparents? On an autosomal DNA test such as those provided by Ancestry or 23andMe, your DNA will always match that of your grandparents – meaning they are DNA matches to you!
Your grandparents are your most recent ancestors, making them part of your direct bloodline and sharing a large proportion of DNA with them. As their descendants descend from you directly, a significant proportion of their genetic material can be found within you as well.
What percentage of your DNA do you inherit from each grandparent?
On average, approximately 25% of each grandparent contributes their DNA. This 25% average shared DNA between a person and each grandparent results from how genetic inheritance works.
Each person inherits 50% of their mother and father’s DNA, as well as 25% from each grandparent (i.e. 25% each for your mom and dad and your grandma and grandpa). We pass down 50% to ourselves from this point forward – making up for any possible differences that might exist due to other influences such as adoption or migration.
Given that our DNA had to come from somewhere, and since we have four grandparents, it stands to reason that around 25% would come from each. Of course, this figure should be seen only as an average.
Your DNA could share 18-33% with any one of your four grandparents. When comparing your DNA with that of one or more of these grandparents, the percentages shared could range anywhere between 18-33%.
Theory allows for variations outside this range; most likely however, shared DNA with grandparents falls somewhere within its middle range, leading to an “average” of 25%.
Why there is such a wide variation of shared DNA among grandparents has nothing to do with which grandparent you resemble most, the amount you share, gender differences or sexual preference; rather it explains the random way DNA is passed down that accounts for this variance among relatives – even close ones such as grandparents.
Your mother and father each inherited 50% of their DNA from each of their respective grandparents; however, through a process known as recombination this 50% was chosen specifically by these two people as your ancestors’ DNA was passed onto them through your genes.
Recombination in DNA inheritance creates a completely unique copy of every chromosome using bits from both copies; only 50% of its DNA may be passed down, meaning 50% remains unspread in future generations.
Your grandparents each possess two copies of each of their 22 numbered chromosomes (called autosomes). Your parent inherited one copy from each parent to equal two total copies for every number chromosome in total.
This process then repeated itself with you, which explains why only 25% of your DNA will likely be shared between any two grandparents and that it’s unlikely for more than 18% or 33% to share among both paternal and maternal grandparents.
How many centimorgans (cMs) of DNA do I share with a grandparent?
On average, we anticipate about 900 centimorgans (cMs) to be shared between grandparents or grandchildren; the range can go from 1300-2300 centimorgans (cMs).
There is a statistically small chance that you could share slightly under or slightly above 2300 cMs with one or both grandparents, meaning someone outside our typical range could still be your grandparent – especially if other evidence points this way.
How many DNA segments do I share with my grandparent? In assessing relationships between grandparents and grandchildren, the percentage or centimorgans of shared DNA should be taken into consideration; grandchildren often possess significant DNA shares with both sets.
However, many individuals are curious to know the percentage of DNA segments shared between relatives due to such wide variance. Recombination processes account for this disparateness – I described them in part one.
For this post, I analyzed shared DNA segments between several sets of grandchildren and grandparents comprising male/female combinations and found 19-29 shared segments on average; 25 were present most frequently (mode).
Size matters when determining how closely two people are related. Thus, I will present evidence from my very small study showing the range of longest shared DNA segments between grandchildren and their grandparents being between 145-220cMs.
An AncestryDNA match list shows an example of shared DNA between an individual and their grandparent; here it’s my paternal grandmother in this instance!
Noteworthy is the fact that I received 27% of my DNA from my grandmother – my father’s mother. This translated to approximately 1855 cMs across 25 DNA segments.
I wouldn’t be alarmed if my DNA shared significantly less with my grandmother than is expected – sharing less than 1000 or even 2000 cMs is perfectly normal with grandparents.
One conclusion I can draw is that I must have shared approximately 23% of my DNA with my paternal grandfather since 50 % must have come from either of my two paternal grandparents.
My maternal grandparents must each contribute 50% of my DNA.
What Can Be Gained from DNA Results of Grandparents? Incorporating DNA results of grandparents can provide valuable insight into where your ancestors may have lived over the last several hundred years and your family tree. You may discover ethnicity regions which don’t appear prominently in your results but still add vital clues.
Indeed, your grandparents could carry regions that match their DNA that don’t appear in your results – this could be due to some strands not passing down which could match additional regions; testing grandparent(s) can provide valuable insight. If possible, having both sets of grandparents tested is highly advised!
Your grandparents likely possess DNA matches that do not appear on your list; similar to how ethnicity estimates vary, these matches likely come from DNA that matches other relatives that were passed down but did not get passed onto you.
Furthermore, your grandparents likely share more DNA with DNA matches than you do and can offer valuable clues as to whether any relationships may exist between themselves and you.
All this information will prove to be incredibly beneficial in building and exploring your family tree, while uncovering its rich history.
Conclusion I hope this post has provided all of the answers you were searching for regarding percentage and centimorgans of DNA shared between grandchild and grandparents as well as anything related to this fascinating topic.
If you have any inquiries or would like to share how much DNA you share with your grandparents, or would simply like a chance to discuss anything read here in this post, feel free to join the discussion in the comment section. I welcome all contributions below!
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