The Khoisan people.
Image: Marczawel.com
From local research into our ancestry to working out the genetic lineages of the earliest modern humans in southern Africa, Quest looks at how science is unravelling the origins of humankind.
The dawn of humankind
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Interpreting mitochondrial DNA results Scientists from the MRC, NHLS and Wits University have been taking samples of blood from volunteers across South Africa to determine our genetic ancestry.
How are the results interpreted?
After they obtain samples of a volunteer’s mtDNA control region (this region does not code for any proteins and is highly prone to mutations) sequence in the laboratory, they compare the person’s sequence profile for this region (e.g. #HS as shown below) to a published sequence called the Cambridge Reference Sequence (CRS). They use about 800 base pairs of sequence from two specific regions within the control region where mutations are more concentrated and
therefore referred to as ‘hypervariable regions (HVRI and HVRII)’. They start reading the HVRI between positions 15961 to 16561 (starting at the position of the ▼ to the end of the sequence below) and HVRII (positions 31 to 407; data not shown). If a person’s sequence differs from the CRS at any position, they note the position and mark the change(s) or mutation(s) as shown in red in the diagram. Using the information, they then list the mutations and the positions at
HVRI
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e can reconstruct human history using a number of different methods. In the absence of written records, scholars have made use of information from disciplines as diverse as linguistics, archaeology, physical anthropology, cultural anthropology, history and paleo-anthropology to reconstruct their prehistory. The most direct account of our past is inferred from the fossil record. Skeletal remains have been instrumental in establishing the evolution of human ancestors in Africa, and they have also provided important information about the evolution of modern Homo sapiens. We all identify with the family unit: our siblings, parents, grandparents, great-grandparents and so forth. We are quick to recognise certain physical traits (characteristics) like hair colour, nose shape, etc., as well as behavioural traits, like temperament, voice, etc., that we attribute to having been inherited from one and/or the other parent. The concept of ancestry is deeply rooted in the different cultures. Paying respect to our ancestors is part of our cultural evolution. The thread that connects us biologically with our ancestry is stored in the human genome that carries biochemical instructions that determine inherited traits, and contains an indelible record of our evolutionary past.
▼start of sequence data
CRS 15961 GAAAAAGTCT TTAACTCCAC CATTAGCACC CAAAGCTAAG ATTCTAATTT AAACTATTCT #HS 15961 GAAAAAGTCT TTAACTCCAC CATTAGCACC CAAAGCTAAG ATTCTAATTT AAACTATTCT CRS 16021 CTGTTCTTTC ATGGGGAAGC AGATTTGGGT ACCACCCAAG TATTGACTCA CCCATCAACA #HS 16021 CTGTTCTTTC ATGGGGAAGC AGATTTGGGT GCCACCCAAG TATTGACTCA CCCATCAACA CRS 16081 ACCGCTATGT ATTTCGTACA TTACTGCCAG CCACCATGAA TATTGTACGG TACCATAAAT #HS 16081 ACCGCTATGT ATTTCGTACA TTACTGCCAG CCACCATGAA TATTGTACGG TACCATAAAT CRS 16141 ACTTGACCAC CTGTAGTACA TAAAAACCCA ATCCACATCA AAACCCCCTC CCCATGCTTA #HS 16141 ACTTGACCAC CTGTAGTACA wTAAAAACCCA ATCCACATCA AAACCCCCTC CCCATGCTTA CRS 16201 CAAGCAAGTA CAGCAATCAA CCCTCAACTA TCACACATCA ACTGCAACTC CAAAGCCACC #HS 16201 CAAGCAAGTA CAGCAATCAA CCCTCAACTA TCATACATCA ACTGCAACTC CAAGGCCACC CRS 16261 CCTCACCCAC TAGGATACCA ACAAACCTAC CCACCCTTAA CAGTACATAG TACATAAAGC #HS 16261 CCTCACCCAC TAGGATACCA ACAAACCTAC CCACCCTTAA CAGTACATAG TACATAAAGC CRS 16321 CATTTACCGT ACATAGCACA TTACAGTCAA ATCCCTTCTC GTCCCCATGG ATGACCCCCC #HS 16321 CATTTACCGT ACATAGCACA TTACAGTCAA ATCCCTTCTC GTCCCCATGG ATGACCCCCC CRS 16381 TCAGATAGGG GTCCCTTGAC CACCATCCTC CGTGAAATCA ATATCCCGCA CAAGAGTGCT #HS 16381 TCAGATAGGG GTCCCTTGAC CACCATCCTC CGTGAAATCA ATATCCCGCA CAAGAGTGCT CRS 16441 ACTCTCCTCG CTCCGGGCCC ATAACACTTG GGGGTAGCTA AAGTGAACTG TATCCGACAT #HS 16441 ACTCTCCTCG CTCCGGGCCC ATAACACTTG GGGGTAGCTA AAGTGAACTG TATCCGACAT CRS 16501 CTGGTTCCTA CTTCAGGGTC ATAAAGCCTA AATAGCCCAC ACGTTCCCCT TAAATAAGAC #HS 16501 CTGGTTCCTA CTTCAGGGTC ATAAAGCCTA AATAGCCCAC ACGTTCCCCT TAAATAAGAC CRS 16561 ATCACGATG #HS 16561 ATCACGATG end of sequence data
Quest 7(3) 2011 7