Name: What Your Family History Can’t Tell You
Uploaded: 2020-04-13T16:07:45.000Z
Duration: 6 min 41 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

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Thanks to the National Institutes of Health's

they'll probably ask about your family history.

Everything from heart disease to certain cancers

to type 2 diabetes—if one of your close relatives has had it,

These family histories can give your doctor a sense

of whether you, too, might carry an increased genetic risk

Not a complete sense, though—because it turns out

family history doesn't tell you everything about the risks

And to understand why, you have to look at

even beyond family history—is pretty straightforward,

because in some cases, a mutation in a single gene

can greatly increase your risk for a given disease.

Take the genes BRCA1 and BRCA2, for example.

Variants or mutations in those genes can give you a

45 to 65% chance of developing breast cancer

That's no joke—and something your doctor can help determine based on your family history.

They might recommend that you take a genetic test,

for example, if you have relatives with BRCA mutations

They're only present in a very small percentage of the population.

Researchers used to chalk this up to a hard and

fast line between sporadic and hereditary disease.

Hereditary disease is one that you, you know, inherit.

A sporadic one isn't inherited—it's seemingly caused by

something in your environment, or something else.

Except that distinction is starting to break down

a huge risk all by itself—like BRCA1 or 2.

Other times, though, it's more like a thousand little cuts,

because lots of genes are involved in increasing

Basically, a large number of gene variants each contribute

a teeny tiny amount to your risk of heart disease,

the more of them you inherit, the greater your risk.

That's true even if your parents or grandparents never got sick.

So from the point of view of your family history,

it wouldn't seem like you're at risk—even though you are.

We can detect the genetic part of these many-gene

or polygenic diseases, though, now that we have

One of the most important tools that whole genome

sequencing has given us is a type of study called

a genome-wide association study, or GWAS for short.

These studies examine genetic data from a huge number

of people—though, usually, there's no need

Instead, researchers look for genetic variants

called single-nucleotide polymorphisms, or SNPs.

These SNPs aren't necessarily the variants causing

an increase in your disease risk, mind you.

They may just happen to lie in close proximity

to the ones that did, and because of that,

By surveying for SNPs and inheritance patterns

in these large studies, we can finally see the thousand cuts

And “thousands” isn't an exaggeration.

Sometimes, we can identify literally thousands

of variants associated with genetic risk.

GWAS have identified genomic variants that can

contribute a tiny amount to your risk of a given disease,

even when you account for your lifestyle and your environment.

Though, figuring out just how at-risk a person

is of developing a given condition is not as simple

Risk variants can synergize or cancel each other

out in complex ways, so researchers have to do

The result of this math is something called a polygenic risk score:

a number that assigns a person's risk for a given disease

based on the combination of genomic variants they have.

And these numbers are helping us to understand

the genetic nature of diseases we used to think were sporadic.

Consider a study published in 2018 in the journal

They calculated a polygenic risk score for

coronary artery disease and found that 8% of their

study population had a three-fold greater risk

That's twenty times more at-risk people than

previous research could identify based on looking for

Or, consider another 2018 study which calculated

a polygenic risk score for aggressive prostate cancer.

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What Your Family History Can’t Tell You

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