What’s a CentiMorgan, Anyway? How DNA Tests for Family History Measure Genetic Relationships
If you’re doing DNA tests for family history, you may see lots of predicted cousin matches: 2nd, 3rd, 4th, etc…..But what does that predicted genetic relationship actually mean? Learn about centimorgans, the powerful genetic genealogy unit of measure, and how it helps your research.
How DNA Tests Measure Genetic Relationships
When we are looking at genetic relationships, there are also many ways we can measure them. But ultimately, we want the testing company to tell us how likely it is that a particular individual shares a single, recent common ancestor with us. One factor in this calculation is to take into account the total amount of DNA we share with that match.
Currently, all the testing companies are reporting this sum in centimorgans (cMs). Every company reports to you the total number of shared cMs, as outlined below.
AncestryDNA: Click on the match to access the personal profile page for that match. In the second section, under Predicted Relationship, you will see the confidence level. To the right of the confidence level, you will see a grey circle with a little “i” in it. Clicking there will show you the total amount of shared cMs as well as how many pieces of DNA you share.
- Family Tree DNA: On the main match page for your Family Finder results, you will see the total amount of shared cMs in the third column.
- 23andMe: You can see the percentage of shared DNA from the main DNA Relatives home page. To convert the percentage into centimorgans, just multiply your percentage by 68 (that will at least get you close). You can also see total shared cMs in the chromosome browser tool (go to Tools > DNA Relatives > DNA).
- MyHeritageDNA: The total amount of shared DNA is shown on the main match page under the title Match Quality. MyHeritage also has a new DNA Match Review page. Click here to read more about that.
Centimorgan: A Genetic “Crystal Ball”
It is very tempting to think of a cM just like you would think of an inch or a centimeter, and for all practical purposes, that is okay. But it is actually much more complicated than that.
A cM is actually more like a crystal ball: it helps us predict how likely a piece of DNA looks exactly as it did a generation ago. This, in turn, helps us calculate how far back we should be looking for the common ancestor between two people.
But for our practical purposes, you can use the total amount of shared DNA, in combination with this chart compiled by Blaine Bettinger and the Shared cM Project, to better assess your genealogical relationship with your match based on your genetics.
To use the chart, take the total amount of shared DNA you have with a match, and look up that number in the chart to get an idea of what kind of genealogical relationship might best fit the genetics that you see. For example, if I share 69 cM with my match, we might be third cousins. But we might also be second cousins once or twice removed.
How do you figure out which one? Simply put: do genealogy research! It’s time to use traditional records and research skills to better understand the genetic clues in your family history mysteries.
My series of DNA quick reference guides can help you get the most out of your DNA tests for family history. I definitely recommend the value-priced bundle of all 10 guides. But I especially recommend the guides listed below if you’re to the point where you’re trying to understand what genetic relationships mean:
- A Guide to AncestryDNA
- A Guide to Family Finder at Family Tree DNA
- A Guide to 23andMe DNA
- Breaking Down Brick Walls with DNA
- Organizing Your DNA Matches
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RootsTech 2014: Use your iPad for Genealogy Research at the Family History Library
Thinking about attending RootsTech in Salt Lake City, Utah in 2014? Then I’m guessing a trip to the Family History Library (FHL) is part
of your plan. Here’s a great tip: bring your iPad or tablet computer and don’t make a single photocopy while you’re there!
Last year, I spent two days researching at the FHL before RootsTech got going. I was up and down a lot between floors, looking at all kinds of books, microfilmed and microfiched materials and even big old maps. On a previous trip, I would have spent a LOT of money on photocopying, even though the copy services there are very low priced. I would have wanted color copies of the maps, so that would have cost more. I would have wasted a lot of time in line to use the copiers–time I would have wanted to spend researching.
But I didn’t waste any time or money. I used my iPad. I have a generation 4 with the rear-facing, 5 megapixel camera, and I used it practically nonstop…
1. Copying material from books. Whenever I found a book page (or a few pages) I wanted to copy, I first imaged the cover pages with the source citation info. Then I imaged the inside pages, making sure the image captured the page number. When I needed to record that a book didn’t have anything on my ancestors, I put a sticky note on the inside front cover saying “checked for Johnsons, didn’t find” (or whatever), then imaged the page with the sticky note on it. This was easy and fast. I sometimes imaged books while standing right in the library stacks! I didn’t have a scanning app on my iPad at the time, but remember you can also use an app like Scanner Pro to scan multipage documents, convert them to PDFs and straighten out and enhance the images.
2. Copying material from microfilm. Okay, it’s not perfect quality, but you can take decent digital images of microfilmed material right from the microfilm reader. First, image the microfilmed page at the beginning saying what the source is (or a note with the source description or even the box with the microfilm number on it). Then stand just in front of the microfilm reader with the iPad. Point the camera down to the displayed image, taking care not to block the projection of the image from the reader above. Here’s an example of what it looks like. Like I said, it’s not perfect because of the angle and lighting. Glare can be a problem so you may want to take a few shots. But you can read these images and most of the time, you don’t need keepsake quality out of microfilm. You just need to capture data. I followed up with some cropping and enhancement editing right on my iPad.
3. Copying material from a map or other folio items. The same general idea applies to imaging maps and other oversized materials. First, image the source citation information, often found on a label at the bottom of the page or on the back. Image the map key, including which way is north, scale, and other details. Then image as much of the map as possible to get an “establishing shot.” Finally, zoom in to the areas of greatest importance to you. Again, it’s not perfect. Laminated items may have glare issues as you can see by the shot shown here. But you may get what you need out of your digital image, especially if you move around so the glare isn’t covering the important areas on the map.
Remember to organize all your images when you get back to your hotel room or home while your memory of the visit is still fresh. Keep source citation shots together with the images you took. Load them into Evernote, if you use it. Organize them as you would other computerized research materials: in surname files, etc.
Finally, remember that fair use and copyright laws still apply to all images you take, whether on a photocopier or your personal digitizing equipment. The Family History Library does allow people to take their own digital images, but not all libraries and archives do. Some repositories rely on the income from copying to fund their facilities. ASK before using your iPad at other libraries! But as you can see, you can save yourself time and money–and have all your research notes and copies already digitized and ready for use on-the-go.
This post was written by Genealogy Gems Contributing Editor Sunny Morton. (Just so you know, I’m not a longtime iPad pro. I learned everything I know about using an iPad for genealogy from reading Turn Your iPad into a Genealogy Powerhouse. Then I adapted what Lisa taught me for the way I research.)
Find Genealogy Apps with the FamilySearch App Gallery
Do you ever wonder whether you’re missing something when you browse iTunes or Google Play for genealogy apps? Well, FamilySearch has created a space JUST for family history apps: The FamilySearch App Gallery.
According to a FamilySearch press release, the gallery helps people “more easily find the right application from FamilySearch’s many partner applications, or services, to enhance their family history efforts. With just a few clicks, patrons can now begin to search partner apps to find those that meet their specific need.”
For example, you can search the App Gallery by:
- what the app does (family tree software, find ancestor, photos and stories, charts and tree views and tree analyzing);
- platform (web, windows, Mac OS, Android, iPhone/iPad and Windows phone);
- price (free for everyone, one-time payment, subscription, or free trial);
- language (English, French, German, Italian, Spanish, Portuguese and more);
- and FamilySearch compatibility (reads from FS, updates into FS or FS account not required).
Remember, the nature of apps is usually very specific. The BillionGraves for Android (or iOS) app, for example, lets you image and index gravestones for the BillionGraves website. But you may not have ever come across some of these apps before–and may find them very useful for your current or future research. For example, Historic Journals lets you run your own indexing project with your own group. You can tag, index, share or archive historic documents in a public or private environment.
I’m pleased to report that the Genealogy Gems Podcast app for iOS and Android are in the FamilySearch App Gallery! In case you don’t already know about the Genealogy Gems Podcast app, it brings the free Genealogy Gems Podcast to your smart phone or tablet along with exclusive bonus material. And in January the app celebrated it’s 5th anniversary! In addition to getting access to the show, you’ll also receive access to special features like PDFs with tips and ideas from the show; Genealogy Gems wallpaper; bonus audio and video content; the ability to follow the show on Twitter; and call-in audio comment feature (iPhone only). (Not all features available for all episodes.)
While the FamilySearch App Gallery is a great resource, it isn’t a comprehensive home for ALL family history related apps. And a lot of genealogy-friendly apps aren’t categorized as such in Google Play or the App Store. Learn more about TONS of apps to further YOUR family history in Lisa’s book Turn Your iPad into a Genealogy Powerhouse. This book introduces you to the tablet/iPad way of “thinking” (it’s different than how you use a computer). It gives you an in-depth look at over 65 genealogy-friendly apps, 32 fabulous tips and tricks and links to online videos where you can watch things for yourself. Got a tablet? No problem–apps available in Google Play are included, and the tips include clues about features to look for in your brand of tablet.
Create a Family History Website with Your Tree
Recently I heard from David with this question:
“Because of your consistent message of starting a family blog [and] anecdotal success from listeners, I started a family history website. A blog just seemed too small…. The ultimate goal is to display the family information for my known relatives as well as create a site that will pop up on Google search results and hopefully put me in contact with new relatives.
My question is about displaying the family tree on the website. I want to have a page that shows my family tree. I did not know how to accomplish that, so I decided to include links to my ancestry and myheritage family trees. The problem with this method is that ancestry requires you to have an account to view the tree, and MyHeritage only shows you some of the family tree and requires an account to view the rest. This is not a great method to share the family tree with relatives because not everyone has, or wants, an account with these sites. Is there a website where I can upload my family tree’s GEDCOM file and then link to it on my website where it will display all the members of my tree?”
It’s always great to hear that Genealogy Gems is helping out. Congrats on the website David! I recommend blogs to my readers because they are quicker and easier to set up, but in reality I would rather recommend they create a family history website like you are doing. It’s better suited for the long haul of getting your word out and connecting with others.
You pose a great question, and so I did what I just coached everyone in my latest episode #171 to do: just Google it! What you are describing is a ‘website plugin’ so I Googled: family tree website plugin and…Ta-da! There are some out there.
I found one for Word Press (which is where I build my site) so I may have to give that one a try. However, since you are using Weebly I went back and added “weebly” to the search and there are definitely some hits there, though I’m not sure if they specifically include a visual tree plug in. Try the searches and see if you find something you like.
My friend Caroline Pointer has a YouTube video called “Build a Family History Website & Blog on Weebly.” Around the 5:50 mark she shows how she embedded family tree charts into Weebly. Looks like she used Scribd.
Keep up the great work on your family history site!