Junk DNA: Not So Junky Anymore

Is Junk DNA Really Junky?

By Sam Kean

The delicious, religious debate over what most of our genome is good for.

Dancers' interpretation of DNA loops

Courtesy of Tom Whipps/Nature

In the 12 years since the human genome was sequenced, so many critters have had their DNA deciphered—oysters, bees, eels, camels, clawed frogs, elephant sharks—that it’s hard to suppress a yawn sometimes. But every so often, a genome cuts through the indifference and makes geneticists’ eyes goggle out. Take the humped bladderwort, a humble aquatic plant whoseDNA was sequenced this past May.

The humped bladderwort has yellow, snapdragon-like flowers, and it’s actually carnivorous, capable of trapping and eating not just insects but even tadpoles and tiny fish. But this combination of beauty and death isn’t what makes the bladderwort special. Most organisms have loads of junk DNA—less pejoratively, noncoding DNA—cluttering their cells. The bladderwort doesn’t: 97 percent of its DNA is classic, hardworking, protein-building DNA. And that lean, mean bladderwort DNA challenges some trendy notions about how all DNA works, including (if not especially) in human beings.

First, a primer on junk DNA, one of the most reviled terms in science. Anyone who took Bio 101 remembers (if only vaguely) that DNA gets turned into RNA, which in turn gets turned into proteins. The protein-producing stretches of DNA are called genes, and genes reside on much longer molecules called chromosomes.

A century ago, as biologists came to grips with the vast number of different proteins needed to build and maintain the body, they decided that genes must be packed very tightly together on chromosomes, since tight packing would be more efficient. They couldn’t have been more wrong. In humans, a typical species in this regard, less than 2 percent of our 3 billion letters of DNA actually builds proteins. Chromosomes were more like vast Saharan wastelands, broken up only sporadically by oases of genes.

So what does that extra 98 percent do? Here’s where things get contentious. Some of the excess—the pseudogenes, the transposons, the tedious stretches where Mother Nature held her fingers down on the keyboard (ACACACACACA ... )—does look like garbage. Heck, 8 percent of our genome is nothing but old, broken-down virus DNA, the genetic equivalent of a Pontiac Firebird on cinderblocks. The name junk DNAemerged in the early 1970s as a catchall term for this cruft.

Even at the time, though, some scientists objected to the term as too dismissive. Molecular biologists had already discovered bits of junk that, far from being irrelevant, actually managed genes: They turned genes on or off and regulated when and where genes were active. As more and more examples of this type of control emerged in the 1980s, the term junk DNA seemed less and less appropriate.

Cont. here:
http://www.slate.com/articles/health_and_science/human_genome/2013/10/junk_dna_debate_critics_of_the_encode_project_cite_humped_bladderwort.html





© History Chasers Click here to view all recent Historical Melungeons Blog posts

Enter your email address to start receiving this blog in your inbox

Enter your email address:
Delivered by FeedBurner

DNA Testing and the Melungeons

Thanks to the Melungeon Historical Society for permission to post this article that was written for them.

Roberta Estes, copyright 2006-2008, restes@comcast.net

DNA testing has become an integral part of any genealogical endeavor, generally as part of a surname project. However, genealogy testing for a larger group purpose, such as the Melungeons, poses some unique challenges.

As the DNA advisor for the Melungeon DNA projects, I would like to take this opportunity to discuss DNA testing, the various types of tests, how they work and why they are important to the Melungeon Historical Society and research process as well as to the personal genealogical research of each participant.

Before discussing how DNA works, let’s first talk about the kinds of questions we would like to attempt to answer by using various types of DNA testing.

1. Are the individuals of the same last name living in the primary Melungeon “home area” of Hancock and Hawkins County (and other very nearby locations) related on their paternal ancestral line? This means, for example, are all of the various Collins families (by way of example) from a common male ancestor?

2. Are the various individuals in this area related to the same maternal lines? This means are there “founding mothers” of this group? This is an important question because in both African and Native American cultures, families were matrilineal in nature, meaning that the surnames could be the same, from the mother, but the fathers in that social culture could be different.

3. How much truth is there to the various reports of African, Native American and Portuguese ancestry within the descendant families? Which families are admixed and can we determine the source of that admixture?

4. Can we tell, using DNA, the source of the Melungeons as a population group? Is the source of the entire group the same, or are there different subgroups? Can we eliminate or lend support to any of the proposed theories, such as shipwrecked sailors, descendants of the Lost Colony, “white Indians”, and others?

5. Can we connect the genealogy of the individuals, the documented historical records of the families, the recorded history of the areas where they are found in the earliest records and along the migration path to Hawkins/Hancock and the DNA to create an answer to the question, “who were the Melungeons and where did they come from”?

6. Are other groups, such as the Redbones, Brass Ankles, Carmel Indians, Salyersville Indians, Lumbee, Saponi and others, specifically other similar tri-racial isolate groups, related to the Melungeons, and if so, how? Perhaps in some cases the proper question is “are the Melungeons and these groups descended from common ancestors”, and of so, who, when and where?

Other questions may arise from the answers, such as “if your surname matches a core Melungeon surname, and your DNA matches as well, but your genealogy does not take you back to Hawkins/Hancock, are you a Melungeon”? These kinds of social and identity questions are not DNA-related questions and it is not my goal to address these kinds of issues.

Let’s take a look at how DNA testing works and the various types of DNA testing available in the market today and how they can address the various Melungeon scientific questions we have set forth above.

The company we have selected to be our partner for DNA testing is Family Tree DNA. This discussion will reference their tests and products. Family Tree DNA provides us with surname projects, geographical projects like the Melungeon project and related projects like the Cumberland Gap and Lumbee projects, as well as haplogroup projects for research. For participants, they provide a personal web page, e-mail notifications of matches, customer support, the benefits of project administrators and more. Some of the graphics below are courtesy of Family Tree DNA as well.
continue here