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Hi, my name is Giles Yeo, and
I'm a geneticist based at
the University of Cambridge.
This lecture is entitled 'Genetic
Testing: Prediction vs Risk'.
We'll go into why I'm talking
about this in a moment, but
in effect we're talking about what
genetic testing can tell you and
how much of genetic testing is predictive,
meaning that given a specific genotype
you can predict a specific phenotype or
a specific disease, and how much
of it is just speaking about risk.
We'll go through this
as the lecture goes on.
Whenever we think about genetics,
we think about Mendel and his peas.
Mendel was an Austrian monk
who was growing peas and
trying to figure out what was responsible
for the peas having specific colours.
He came up with the concept of dominance,
where one colour was dominant
over another, or recessive,
meaning that two copies of a specific
gene were needed in order to give
the pea colouration that he wanted.
He was the father of genetics as
we consider it today, so much so
that we now have these conditions
called Mendelian conditions,
from the name Mendel.
These are genetic conditions with 100%
penetrance, which means that if you
have a specific mutation in a given gene,
you will get a specific disease.
For example, cystic fibrosis is what we
call an autosomal recessive condition,
autosomal means that the mutation is not
on a sex chromosome, and recessive means
that you need two copies of a specific
mutation in order to give you a disease.
Giles Yeo: Cystic fibrosis is caused by
mutations on an autosomal chromosome, and
you need two copies of
the mutation to see the disease.
The next one we have here is
Duchenne's Muscular Dystrophy.
This is an X-linked recessive disease,
which means that it's
a mutation on chromosome X.
And it's recessive in a sense, so
you need both copies of the gene to be
mutated if you are female, but as a male
because you only have one X chromosome,
then any mutation on the X
chromosome will lead to the disease,
thus it's called an X-linked
The final one listed here
is Huntington's disease,
which is an autosomal dominant mutation.
The mutation happens not on the sex
chromosome and you only need one mutation,
because the mutation is dominant you
will actually end up with the disease.
So many of us will have studied
this in high school and
I'm sorry if this is 'teaching Grandma to
suck eggs', but I thought we should begin
from an even playing field so
we all understand what's going on.
The first question relates
to how we look at DNA, so