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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.

genetic relationships and centimorgans

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:

Thanks for sharing this post with someone who would enjoy reading it! You’re a gem!

Disclosure: This article contains affiliate links and Genealogy Gems will be compensated if you make a purchase after clicking on these links (at no additional cost to you). Thank you for supporting Genealogy Gems!

RootsTech 2014: Use your iPad for Genealogy Research at the Family History Library

RT-Blogger-badge-150sqThinking 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.

sunny_morton 100 px

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.)

 

 

 

 

Episode 265 Writing a Family History Book with Author J.M. Phillips

Show Notes: If you’ve been wondering how to write and self-publish a book about your family history, my guest has answers for you! In this episode author J.M. Phillips shares:

  • How to be a great family history storyteller
  • Her favorite writing techniques that help create a compelling story
  • What she learned about self-publishing (and what you need to know)
  • Her experience living on and writing about Lamlash Street

Click here for the full show notes.

Listen to the Podcast

 
Amazon Link to Buy the Book

Click here to buy the book. (Thank you for using this link which helps make this free show possible.) J.M. Phillips is the author of the new book Lamlash Street, A Portrait of 1960’s Post-War London Through One Family’s Story available at Amazon in paperback or Kindle. 

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Genealogy Gems Podcast Episode 251

Free Online Records at the Allen County Public Library Genealogy Center

If you’re looking for a wide array of free online genealogical records for your family history, look no further than then Allen County Public Library’s Genealogy Center in Fort Wayne, Indiana. It’s the second largest genealogy library in the country. In addition to the in-house collection, the Genealogy Center offers a vast amount of free digitized resources through their website and partnerships with other websites. 

I invited Allison Singleton, Senior Librarian at the Allen County Public Library Genealogy Center in Fort Wayne, Indiana to the show. She is taking us on a tour of the website and sharing her tips and strategies for finding genealogy gems. 

To Listen click the media player below (AUDIO ONLY):

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This audio from this episode comes from Elevenses with Lisa episode 31. Log into your membership and then click here to download the handy PDF show notes that compliment this podcast episode. 

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Don’t miss the Bonus audio for this episode. In the app, tap the gift box icon just under the media player. Get the app here

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MyHeritage.com is the place to make connections with relatives overseas, particularly with those who may still live in your ancestral homeland. 

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Show Notes: The audio in this episode comes from Elevenses with Lisa Episode 31. Visit the show notes page here. 

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