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This talk is
on chromatin genes and disease.
And my name is Richard Gibbons.
And I'm a clinical geneticist
and molecular biologist working
in the MRC molecular
hematology unit,
and the Weatherall Institute
of Molecular Medicine, which
is part of the University of Oxford.
My particular interests are
in how genes are regulated.
That's how they're
turned on and off.
And in the field of epigenetics.
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So what does this term mean?
It accounts for differences in
the phenotype type of cells,
or organisms that are
genetically identical.
It's involved in alterations
in gene expression.
And also, the important thing is,
this pattern of gene expression
is maintained on cell division.
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For instance, these different
organisms here, the caterpillar,
the chrysalis, and the butterfly,
are genetically identical.
But they're
phenotypically different.
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Here we see a tortoiseshell cat.
And the different coat color it
has, the orange and black stripes,
are from cells that are
genetically identical,
but they produce the
different colors.
And this is because the coat color
genes are on the X chromosome,
although this female
has two X chromosomes.
And in any one cell, any
one of those Xs is active.
It's called X inactivation.
So if the paternal X encodes for the
black color, and maternal X encodes
for the orange color, in any one
cell, only one will be active.
And the progeny of those cells
will have the same pattern.
So you give rise to this
mosaic pattern of coloring,
depending on which X is active.
But the important thing is,
those cells are genetically
identical, but
epigenetically different.
