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Y-chomosome STR testing |
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This tutorial will help you understand how to use DNA in your genealogical research. It's quite long (4 pages) but you'll be an expert
by the end of it!
Or for those that can't wait, there's our 60 second tutorial. |
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DNA Heritage looks at the DNA in the Y-chromosome within males.
This
is one of the sex chromosomes and is responsible for maleness. All
males
have one in each cell and copies are passed down (virtually) unchanged
from father to son every generation.
Therefore, the Y-chromosome test is solely for males,
but can be a cousin, brother or other male relative. |
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To understand where DNA comes from we shall put it in the context
of the cell.
Let's take a close look at a cell. Our cell is split in half. |
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Key |
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Cell wall = Blue |
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Nucleus = Yellow |
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Chromosomes = Orange |
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Mitochondria = Red |
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Y-chromosome = Purple |
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We can see that the cell contains a nucleus within its centre. The
nucleus |
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contains the DNA wrapped up in 46 chromosomes. The Y-chromosome
is highlighted in purple.
The cell also contains other structures, like the red mitochondria
shown, which are the 'power packs' of the cell. They make up about
one-fifth of the total cell volume.
Here a close up of the nucleus shows the chromosomes in more detail
(not all are shown). |
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Below is an actual close up of the Y-chromosome which has been enhanced |
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with colour. As in the other illustrations, the Y-chromosome
is purple and the other chromosomes are coloured orange. As
you can see, the Y-chromosome is much smaller than many other
chromosomes - compare it with the X-chromosome pictured centre.
Each chromosome is made up of a very long DNA molecule carefully
wrapped around proteins. |
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If we pull one end of the Y-chromosome
we can start to unravel our model. We
now see the familiar double-helix
structure of DNA.
This is made up of two corkscrew-like
structures connected by lots of smaller
cross-links. |
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If we then untwist and flatten our helix onto the computer screen, |
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a simple ladder-like structure is formed. |
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When DNA is studied, it is only the rungs of the ladder which are
looked |
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at. Our ladder is colour coded. These coloured rungs of our ladder
represent 'complementary bases'.
Notice that whenever a blue base occurs, a red is on the other side.
They fit together thus complementing themselves. Also, yellow
complements green.
| Thymine (Blue) |
= |
T |
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Guanine (Green) |
= |
G |
| Adenine (Red) |
= |
A |
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Cytosine (Yellow) |
= |
C |
So we can rewrite the DNA as:
A
G A C G A T C T G T A C C T C T etc.
Because both sides of the ladder match each other, we need only rewrite
one side out.
When we say the Y-chromosome is passed from father to son, this actually
means the sequence of letters remain the same. |
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