All language subtitles for 17031x_MH_Inferring_Patterns_01_Symbolism_v1-en

MICHAEL HEMANN: In the case of mice and flies and yeast

and model organisms, we can actually

test, we can do experiments, we can increase our numbers to try

to more rigorously test our hypotheses

or exclude particular hypotheses.

Now, we can't do this, again, in humans.

In humans, we actually have to rely on the experiments that

have already been done, which is to say the crosses that people

naturally set up in their lives when they find partners

and they have children and we can actually

look at entire families and family histories.

And so now, we're going to start talking

about this idea of pedigree analysis

and how we look at inheritance patterns in people.

And again, this kind of analysis involves information.

And it involves taking family histories.

So, talking to people and getting a sense from them

in a family who has a particular phenotype.

Did your parents, did your grandparents, did your uncles,

did your aunts, did your children-- can

you assemble as large of a data set as possible

that's going to allow you to infer and hypothesize things

about patterns of inheritance that can tell us information

that informs decisions that people

make about having children or what they should look for?

It also allows us to do extensive mapping studies

to identify the location of genes and alterations

within the genome.

So pedigrees are absolutely essential for all

of the mapping studies that we're going

to talk about in the future.

So there's an established symbolism in pedigrees

that allow us to draw out these family histories.

And some but not all of these symbols are shown here.

And so for example, if you have people

that are unaffected by whatever phenotype you're looking

at-- it doesn't have to be a deleterious condition,

it can just be hair color, or eye color,

or any other characteristic-- we indicate them

as an empty square for males and an empty circle for females.

A line crossed through generally means the person is not around

any longer.

So sometimes, you want to generate pedigrees that have

great-great-grandparents and great-great-great-grandparents

if you have that information available.

When we have a square or a circle that's filled in,

we mean that this person has the phenotype that we care about,

so affected males or affected females.

And generally, if there's a dot inside,

it means that we know by some either genetic analysis

or based on inference-- that we'll talk about--

that they are a carrier.

So mating meaning, an interaction

that leads to offspring, is indicated by a line

between two individuals.

Consanguineous mating-- which is really important in looking

at some syndromes or conditions--

indicates a mating essentially between blood relatives.

And this underlies the etiology of a number

of recessive conditions.

And I'll bring one up in a couple of minutes.

And then we have sort of a reproductive unit

here where we have two people that have children,

and their children are indicated by a line that's

drawn below, having both male and female children.

So these aren't all of the symbols,

but there are many of the symbols that we'll look at.