Abstract

Objective

In this science project you will analyze your DNA to learn about your ancient ancestors.

Introduction

The goal of the National Geographic's Genographic Project is to understand the human journey—where we came from and how we got to where we live today. We know from the fossil record that our species, Homo sapiens, arose in Africa over 100,000 years ago, and then spread throughout the globe over the past 60,000 years or so. Even though we share a common ancestry dating back to Africa, we have clearly grown into a diverse family. Clues explaining this diversity can be found within all of us—it's called our DNA.

When DNA is inherited from one's parents, it is recombined, which means that every chromosome contains a patchwork of DNA from each parent. Two types of DNA that escape recombination are useful for determining lineage: mitochondrial DNA and the Y chromosome. Mitochondrial DNA is passed from mother to children (both male and female), intact; that is, it is identical in the children and the mother, unless a rare mutation occurs. The Y chromosome is passed from father to sons. Again, it is passed along without change, unless the DNA undergoes a rare mutation. Mutations, though rare, can accumulate within a population over long periods of time. When mutations occur in mitochondrial or Y-chromosomal DNA, they have the potential of becoming "markers," or tags that allow geneticists to trace a common lineage back through the ages.

One type of marker is a single nucleotide polymorphism . DNA sequences are polymorphic when there are two or more forms of the sequence within a population. A single nucleotide polymorphism (SNP, pronounced snip) is a DNA sequence variation involving just one nucleotide. Nucleotides are the four bases that are the building blocks of DNA: A, T, C, or G. For example, the sequences ATGC and ATGT are polymorphic at the fourth nucleotide. In the example just given, the SNP can be written as C4T, indicating that the C at position 4 has been changed to a T.

Another type of marker, useful for characterizing the Y-chromosomes, is called a short tandem repeat, or STR. STRs are regions of DNA that contain a repeated sequence. The repeated sequence is short (3 to 5 bases) and it occurs in the same orientation each time it is repeated (tandem). These regions are useful as markers because the number of repeats varies considerably within the human population. The STR called DYS393, for example, can have between 9 and 17 copies of the short sequence AGAT. The Genographic Project looks at 12 different STRs on the Y-chromosome.

In this science project, you will send a sample of your cheek cells to a laboratory. The cells will be broken open and the DNA will be analyzed for the presence of markers that shed light on your ancient past.

You can choose to analyze either your mitochondrial DNA (male or female) or your Y-chromosomal DNA (for males). Mitochondrial DNA traces your maternal lineage. Going back in time, your mitochondrial DNA was copied from your mother, who received her copy form her mother, and so on, going back hundreds of generations. Males get their mitochondrial DNA from their mothers, too, but they do not pass it on to their children. The Y-chromosome, on the other hand, traces your paternal lineage, also going back hundreds of generations, but you only have the chromosome if you are male. If you are a female and would like to learn about your paternal lineage, then a male relative—such as a father, a brother, or a paternal blood relative of your father's, such as his brother—can test his Y-chromosome DNA. The results will reveal a female's paternal lineage.

Your DNA sequence will be compared to a database of DNA sequences from all over the world to look for the best matches. The report you receive from the laboratory will assign you to a haplogroup. The people within a haplogroup share a common ancestry. Members of mitochondrial haplogroup H5, for example, all share a common ancestor who inhabited a region in what is now Great Britain, thousands of years ago.

It is important to remember that we all share a common ancestry, going back to Africa. But haplogroups represent sub-populations with relatively recent common ancestry.

The National Geographic Society's Genographic Project website has a wealth of information about the history of human migrations as revealed by analysis of DNA samples like yours. There are also a number of books, listed in the bibliography, that discuss how modern genetics is helping to define the routes and timelines of ancient migrations out of Africa and into Europe, Asia, Oceana, and the Americas.

NOTE: This is an advanced project involving independent research. You will have to make some decisions for yourself (such as doing a mitochondrial vs. a Y-chromosomal test), and you will have to research advanced topics. The time commitment will pay off as you will learn about your ancient ancestors, and you will be able to explore the secrets of human evolution as revealed in your genetic code.

Terms, Concepts, and Questions to Start Background Research

• DNA
• Mutation
• Marker
• Single Nucleotide Polymorphism (SNP)
• Short Tandem Repeat (STR)
• Haplogroup
• Polymorphism
• Common ancestor

Questions

• What is a polymorphism?
• How are different haplogroups defined?
• Which members of your family share the same mitochondrial DNA? Include your aunts, uncles, and grandparents.
• Which members of your family share the same Y-chromosomal DNA? Include your aunts, uncles, and grandparents.
• After studying the resources on the Genographic Project website, can you predict which haplogroup you will most likely belong to?

Bibliography

• The Genographic Project website has excellent introductory information, including a Genetics Overview and an Atlas of the Human Journey.
  National Geographic Society. (2008). The Genographic Project. Retrieved May 16, 2008 from https://www3.nationalgeographic.com/genographic/
• The National Geographic website has extensive lesson plans tailored for various grade levels.
  National Geographic Society. (2008). Genographic: Mapping the Human Journey. Retrieved May 16, 2008 from http://www.nationalgeographic.com/xpeditions/lessons/09/g912/genographic1.html
• Answers to frequently asked questions about The Genographic Project are available on the Project's FAQ page:
  National Geographic Society. (2008). Genographic Project FAQs. Retrieved May 15, 2008 from https://www3.nationalgeographic.com/genographic/faqs.html
• This site has information about how the DNA tests are performed and how your results will be made available to you.
  The Ancestry DNA Project. Retrieved May 15, 2008 from http://www.familytreedna.com/ftdna_genographic.html#q4
• Read about hundreds of Chicago Public School students who discovered their ancient migratory histories through the Genographic Project.
  National Geographic. (2007, January 23). Who Are You and Where Did You Come from? Tracing Your Ancient Ancestors in the Classroom. Retrieved May 15, 2008 from https://www3.nationalgeographic.com/genographic/silk_route_announcement.html
• The National Center for Biotechnology Information has a website explaining single nucleotide polymorphisms:
  National Center for Biotechnology Information. (2007, September 20). SNPs: Variations on a Theme. Retrieved May 27, 2008 from http://www.ncbi.nlm.nih.gov/About/primer/snps.html
• This site has technical information about short tandem repeats found on the Y-chromosome:
  Butler, J.M. and Reeder, D.J. (2008, January 28). Y-Chromosome STRs. Retrieved May 27, 2008 from http://www.cstl.nist.gov/div831/strbase/y_strs.htm

  There are a number of books about the exciting science that is revealing our genetic ancestry. Here are three noteworthy ones:

• Olson, Steve. Mapping Human History. New York: Houghton Mifflin Company, 2002.
• Sykes, Bryan. The Seven Daughters of Eve. Norton: New York, 2001.
• Wells, Spencer. The Journey of Man. New York: Random House, 2002.

Materials and Equipment

• To analyze your DNA, you will send a sample of your cheek cells (also called buccal cells) to a laboratory for DNA sequencing.
• The kit can be ordered from the National Geographic Genographic Project website: https://www3.nationalgeographic.com/genographic/participate.html. The Participation Kit costs $99.95 (plus shipping and handling, as well as tax, if applicable). The kit includes:
  • Buccal swab kit, instructions and a self-addressed envelope in which to return your cheek swab sample
  • DVD with visual instructions on how to collect a DNA sample using a cheek scraper, and a bonus feature program: the National Geographic Channel/PBS production The Journey of Man
  • National Geographic map illustrating human migratory history
  • Confidential Genographic Project ID # (GPID) to anonymously access your results at the Genographic website
  • Alternatively, you can order the kit directly from Family Tree DNA at http://www.familytreedna.com/, which is the lab that works with the National Geographic Genographic Project to obtain DNA sequence information.

Experimental Procedure

To start this project, you should be familiar with basic genetics and the terms and concepts listed above in the "Terms, Concepts and Questions" section. The Genographic website has good introductory information on these subjects.

1. Order the DNA sample kit from The Genographic Project or Family Tree DNA.
2. You will need your parent's consent to submit a sample for analysis.
3. Carefully review your results when they are available.
4. List your polymorphisms in your lab notebook.
5. Research each polymorphism and write your findings in your lab notebook.
6. Note which polymorphisms were used to assign your DNA to a haplogroup. (The report from the Genographic Project will have this information.)
7. Can you determine roughly when each polymorphism arose in the human population?
8. Research your haplogroup.
9. In what geographic region are members of your haplogroup indigenous?
10. What route did your ancestors take on their migration out of Africa?

Variations

• Compare oral family history with DNA family history. Which takes you back farther? Which provides more detail about recent (last 3-4 generations) migrations?

• For more science project ideas in this area of science, see Genetics & Genomics Project Ideas.

Credits

David B. Whyte, PhD, Science Buddies

Last edit date: 2008-07-23 22:00:00