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DNA is often called the 'molecule of life'. Within it are
the code words that
help build proteins and thus help our bodies to function.
However, most of it doesn't encode for anything at all -
we call these regions 'junk DNA' and they
contain no medical information whatsoever. |
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DNA Heritage uses 43 special markers along
the DNA strand in these |
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'junk' regions to read into the genealogy of the person. At
these markers, the sequence of bases repeats itself many times
(also called STR's - short
tandem repeats). |
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As an example, at a particular marker, our equipment reads
the DNA
sequence as: |
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where TCTA is
repeated 9 times. |
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Because the STR marker is named 'DYS391', we record: DYS391
= 9
At this particular marker, the number of repeats can be
anywhere between 7 and 14. The Y-chromosome is special in
that it doesn't undergo 'shuffling' with each new generation.
When a new baby is conceived, the chromosomes the baby receives
will be a mixture from both mother and father.
But the Y-chromosome only comes from the father so the number
of repeats in a baby boy will be the same as his father.* The diagram below shows the path of the Y-chromosome which travels down all males lines, thus paternally-related cousins will also share the same Y-chromosome. |
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* |
Very occasionally these repeats increase
or decrease, usually one at a time.
That is,
a father
may have
DYS391 =
9 and
his son
DYS391 =
10.
We have gained a TCTA
somewhere!
This is called a mutation and happens when the DNA is
copied slightly incorrectly within the body. It is worth
noting that this is a natural phenomenon and is indicative
of Darwin's 'Theory of Evolution' working at a molecular
scale! |
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These mutations are very useful because otherwise every
male would have exactly the same Y-chromosome. The fact that
related males that share the same surname will have identical
Y-chromosomes (or at least a very close match), is why Y-chromosomes
are so useful to genealogists. It is also very easy to tell
if two males aren't related at all.
Also, because we know roughly how often these changes take
place, we can also estimate when the most recent common ancestor
(MRCA) lived. |
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When we test for many STR's, we obtain a 'haplotype'.
This is simply a sequence of numbers from each marker - a bit
like a combination to a lock. Using a 21-marker test that
DNA Heritage used, your haplotype could look like this:
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The STR markers are labelled along the
top, with the haplotype of the individual given underneath.
So for DYS19, read 14 repeats.
And, for example, at GATA A10 read 12 repeats (note:
GATA and TAGA are also used for naming STR markers). |
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North American office: P.O. Box 1028, Richmond, TX 77406-1028 USA tel/fax: Toll free 866-7-DNA-DNA |
European office: 40 Preston Road, Weymouth, Dorset,
DT3 6PZ, UK tel:+44 (0) 1305 834936 fax:+44 (0)
1305 835925 |
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