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I'd like to estimate what percentage of DNA my sister and I share. I cannot find anywhere on Ancestry.com that states how many total cM's are tested, but another testing website mentioned 6800. I also noticed the Shared cM Project tool equated 100% to 7460 cM. Is anyone familiar with the total number of cM tested by AncestryDNA? Thanks for your help.
Someone in this category is likely a brother or sister who shares both biological parents with you. In the rare situation that you have a half-sibling who is also your first cousin, they may appear in this category too. You will share about 2,400—2,800 centimorgans with a full sibling."
Since there will be some SNPs that Ancestry.com tests for that neither sibling has, you cannot go by the full range of SNPs tested.
I hear ya', and I'm not looking for an exact %, just talking numbers. But when I Google this topic, I just get a bunch of sites that seem to contradict each other.
Another way to express how much DNA you share is in form of percentages. You can convert centiMorgans into percentages simply by dividing the total number of cMs by 68. Why 68? There are roughly 6,800 possible centiMorgans in a person’s DNA. So if you share 3,400 centiMorgans with a match you can say you share 50% of DNA (that is, 3400/6800*100 or simply 3400/68).
2. Also, The Shared cM Project 3.0 tool v4 will take the total number of matching cM and convert it to %, which means it must have a total number of cM in order to make the conversion. From playing with it, that number appears to be about 7460.
3. On the other hand, WhoAreYouMadeOf.com, another website I'd never heard of states:
Quote:
Identical twins who are truly identical will appear as themselves on a DNA test. Depending on the DNA testing company that they test with, it will probably say “Self” in the estimated relationship category. The approximate amount of shared DNA, in centimorgans (cMs) is 3400.
The Shared cM Project tool interprets 3400 cM shared DNA as a 45% match, which seems screwy when talking about truly identical twins. It doesn't feel like it should be a difficult question, but I'm beginning to think it's one that just should be left alone. Thanks for your feedback.
In this case, however, it's not a question of relationship. Our amount of shared DNA matches very closely to the chart's average value for siblings. The question I was asked (by someone not truly interested in the science) was: how closely did we match? At the time, percentages seemed like a simple way to answer the question, but that's beginning to feel naive.
Perhaps, the better answer is to compare our amount of shared DNA to the value expected for identical twins, and let it go at that.
I hear ya', and I'm not looking for an exact %, just talking numbers. But when I Google this topic, I just get a bunch of sites that seem to contradict each other.
2. Also, The Shared cM Project 3.0 tool v4 will take the total number of matching cM and convert it to %, which means it must have a total number of cM in order to make the conversion. From playing with it, that number appears to be about 7460.
3. On the other hand, WhoAreYouMadeOf.com, another website I'd never heard of states:
The Shared cM Project tool interprets 3400 cM shared DNA as a 45% match, which seems screwy when talking about truly identical twins. It doesn't feel like it should be a difficult question, but I'm beginning to think it's one that just should be left alone. Thanks for your feedback.
Identical twins will be identical on both sides of that approximate 3400 cM. Each chromosome has two sides - one side you get from your father, the other from your mother. 3400 cM is the approximate total on one side because that's the approximate length of all the chromosomes combined. The total is not necessarily always expressed as a double of that number, but rather 3400 cM on both sides or "Base Pairs with Full Match". So 3400 cM base pairs with full match would be an identical twin (100%), while 3400 cM base pairs with half match would be a parent/child (50%). But that is an approximate - different companies have different cM totals.
"AncestryDNA uses 3475 as the total cM according to the help screen for confidence level in a DNA match. This presumably excludes the X chromosome."
So including both sides of that the total would be 6,950 cM. Full siblings will share some base pairs with full match and some base pairs with half match.
In this case, however, it's not a question of relationship. Our amount of shared DNA matches very closely to the chart's average value for siblings. The question I was asked (by someone not truly interested in the science) was: how closely did we match? At the time, percentages seemed like a simple way to answer the question, but that's beginning to feel naive.
Perhaps, the better answer is to compare our amount of shared DNA to the value expected for identical twins, and let it go at that.
I see what you're saying with Ancestry. Both my mom and her sister had their DNA tested with Ancestry and all it says is 2,607 centimorgans shared across 66 DNA segments, 100% chance they are sisters (no kidding!), and not really a break down of what overall % they share.
I think My Heritage might be able to answer your question, but you would have to upload your raw DNA and your sister's raw DNA and pay a fee for each. With My Heritage, they have this thing called a chromosome browser and you can select up to 7 other DNA matches and see where you match across each chromosome.
They also give you an overall % of matched DNA. So none of my sisters are on My Heritage or my mother or her sister, but I manage my father's DNA on there and one of his brothers is also on there. So when I click on my father's DNA and go into the chromosome browser and add his brother to compare it says they have 36.6% shared DNA a total of 2,597.6 cM across 46 segments with the largest being 175.1 cM.
I think that 36.6% of shared DNA between the two of them is what you're looking for with you and your sister, no?
I would try My Heritage, but it will cost you a wee bit, too bad Ancestry doesn't have a chromosome browser!
If you do some math using what my father and his brother share, 2,597.6 cM and divide that by 0.366 (% they share), the total cM would be 7,097.3 cM tested.
I see what you're saying with Ancestry. Both my mom and her sister had their DNA tested with Ancestry and all it says is 2,607 centimorgans shared across 66 DNA segments, 100% chance they are sisters (no kidding!), and not really a break down of what overall % they share.
I think My Heritage might be able to answer your question, but you would have to upload your raw DNA and your sister's raw DNA and pay a fee for each. With My Heritage, they have this thing called a chromosome browser and you can select up to 7 other DNA matches and see where you match across each chromosome.
They also give you an overall % of matched DNA. So none of my sisters are on My Heritage or my mother or her sister, but I manage my father's DNA on there and one of his brothers is also on there. So when I click on my father's DNA and go into the chromosome browser and add his brother to compare it says they have 36.6% shared DNA a total of 2,597.6 cM across 46 segments with the largest being 175.1 cM.
I think that 36.6% of shared DNA between the two of them is what you're looking for with you and your sister, no?
I would try My Heritage, but it will cost you a wee bit, too bad Ancestry doesn't have a chromosome browser!
If you do some math using what my father and his brother share, 2,597.6 cM and divide that by 0.366 (% they share), the total cM would be 7,097.3 cM tested.
Agree with my heritage. It's a free upload that gives family matches. The charge is $30 for one test but you'd be able to access all the tools for that one test.
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Thanks for your feedback. 
