Trace Your Ancient Ancestry Through DNA
AbstractDid you ever wonder about your ancient ancestors? Who they were? Where they came from? In this science project, you will investigate the secrets of your distant past as revealed by your DNA. In order to obtain a sample for DNA analysis, you will scrape a soft swab inside your mouth to collect cheek cells. The cheek cell sample will be sent to a lab for processing, and the results of the analysis will be sent to you. Based on the genetic markers in your DNA, the ancient clan that your ancestors belonged to will be identified. The resources you receive back will introduce you to your ancient ancestors and allow you to explore their migrations.
David B. Whyte, PhD, Science Buddies
In this science project you will analyze your DNA to learn about your ancient ancestors.
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. The recombination of DNA makes it useful to look at recent (several generations) of ancestry, but if you want to look back further thousands of years to trace human migration, you need to look at DNA that changes less frequently. There are two types of human DNA which have traditionally been used for this: mitochondrial DNA (mtDNA) and Y chromosome DNA (Y-DNA). Both have very low levels of recombination.
The Y-chromosome is passed from father to son without change, unless the DNA undergoes a rare mutation. Until recently, it was thought that mitochondrial DNA was passed from mother to children (both sons and daughters). New data puts that assumption in doubt. Researchers are still working on confirming this information, but there may be a low rate of mtDNA transfer from fathers to children too. This video is a good starting place to learn more:
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 find a company that does either mitochondrial DNA (mtDNA) or Y-DNA testing and send a sample of your cheek cells to them. 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 (available to males or females) or your Y-chromosomal DNA (available to males only).
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 (several thousand years) common ancestry.
Terms and Concepts
- Single Nucleotide Polymorphism (SNP)
- Short Tandem Repeat (STR)
- Common ancestor
- 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 learning about haplogroups and taking in to account what you know about your family history, can you predict which haplogroup you will most likely belong to?
- Genetic Science Learning Center. (n.d.). Making SNPs Make Sense. University of Utah Health Sciences. Retrieved December 17, 2014.
- 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.
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
Decide on whether you want to analyze your mitochondrial DNA (mt-DNA) or Y chromosome DNA (Y-DNA), then do a web search for a company that specializes in one of those. There are several to choose from.
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.
- Choose and order either a mt-DNA or a Y-DNA kit.
- You will need your parent's consent to submit a sample for analysis.
- Carefully review your results when they are available.
- List your polymorphisms in your lab notebook.
- Research each polymorphism and write your findings in your lab notebook.
- Note which polymorphisms were used to assign your DNA to a haplogroup.
Research your haplogroup. Roughly when did each polymorphism arise in the human population? In what geographic region are members of your haplogroup indigenous? What route did your ancestors take on their migration out of Africa?
Ask an Expert
- Compare oral family history with DNA family history. Which takes you back farther? Which provides more detail about recent (last 3-4 generations) migrations?
- Alu repeats are short (approximately 300 base pair) sections of DNA which appear in different numbers in different human populations. Using the Human Alu DNA Extraction and Amplification from Carolina you can PCR up the Alu repeats from the PV92 region of chromosome 16 from friends and family members and see what this data indicates about their ancestry. You will need access to a lab equipped with a PCR machine, pipettes, and gel electrophoresis equipment to do this project.
If you like this project, you might enjoy exploring these related careers:
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