So you may buy a DNA test to fill out the leaves and branches of your family tree? Hold on — you could be in for an odyssey of discovery and pain.

“DNA [testing] is just like a big roller coaster of emotions.” Bennett told a crowd of about 150 people attending her RootsTech 2018 lecture in the Salt Palace Convention Center on Wednesday. “People talk about being frustrated, overwhelmed, unable to think clearly and speechless” when they get their results.

“There’s also sometimes denial, that ‘this just can’t be true,’” she added. “They are tearful, excited [and some get] cold hands and a lump in the throat, a dry mouth, and some get so irritable they just can’t deal” with the unexpected, even unwelcome heritage revealed by DNA data.

Bennett’s talk was one of hundreds of speeches, workshops and presentations planned during the four-day convention, promoted as the largest of its kind in the world. More than 25,000 family history buffs were registered to attend, with another 50,000 expected to participate in online offerings.

In addition to myriad events for family history researchers — ranging from beginner to intermediate and expert levels — attendees also get to try the latest in genealogical research software and mobile apps.

Bennett focused on how the addition of DNA testing to the highly personal, centuries-old craft of genealogy had stretched well beyond mere science to touch the souls of inquirers.

(Francisco Kjolseth | The Salt Lake Tribune) Geneologist Bernice Bennett speaks on the "emotional side" of DNA testing as the RootsTech Conference attracts thousands to the Salt Palace Convention Center on Wednesday, Feb. 28, 2018.

In her own case, it connected her with a previously unknown first cousin in South Carolina. As the two together followed DNA links to others, Bennett eventually learned that not only had her ancestors been African slaves in the pre-Civil War South, but also that she shared paternal genetic markers with a white slave owner.

For Bennett, that revelation — although historically connected to human bondage and exploitation — fleshed out her history and, as such, she accepted it.

For others, she has helped in their DNA test-aided genealogical expeditions, with results that can bring wildly differing reactions.

“Secret scandals and lies also do exist, and some people will take those to the grave,” Bennett warned, “but they do come out in your DNA.”

So be prepared for revelations both wonderful and distressing, she said, findings that may enrich as well as rewrite the story of who you thought you were, and how you got here.

“What would you do if you found out your father is not your biological father?” Bennett asked. “Or your mother refuses to tell you the name of your father [or that] your sister is your half-sister?”

Such are risks to be prepared for, but there also is the potential for rejoicing, when an adoptee previously without a past connects to birth parents or unexpected siblings.

“Yes, there’s joy,” Bennett said, “because we do sometimes find that connection.”

RootsTech, organized by Family Search, the genealogy arm of The Church of Jesus Christ of Latter-day Saints, continues Friday and Saturday.

On the final day, Dallin H. Oaks, first counselor in the LDS Church’s governing First Presidency, along with his wife, Kristen, will share their family history insights during a 1 p.m. address.

RootsTech concludes with a 6 p.m. musical production at the LDS Church Conference Center, “My Family, Mi Herencia.” That event, celebrating stories and culture from Latin America, also will be streamed live on lds.org/latino2018 in English, Spanish and Portuguese.

(Francisco Kjolseth | The Salt Lake Tribune) The RootsTech Conference attracts thousands to the Salt Palace Convention Center on Wednesday, Feb. 28, 2018.