BBC Science The Theory of (nearly) Everything 2019

THE NEXT BIG STEPS FOR SCIENCE

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by DR NESSA CAREY (@NessaCarey)

Dr Carey is a molecular biologist and

author of The Epigenetics Revolution.

GENETICS

F

rancis Crick and James Watson

became household names for

their 1953 discovery of the

structure of DNA, a breakthrough

that formed the basis for our

understanding of how attributes are

passed on f rom one generation to t he

next. But DNA – the genome – isn’t the

whole of the story.

Since the 1970s, the role of the

‘epigenome’ has come under ever-

greater scrutiny. The epigenome is

the name given to tiny chemical

modifications, to DNA and the

proteins it wraps around, made by

factors such as environment and diet.

So, while your green eyes or dark

skin are due to the DNA you inherited

from your mother, your wiry build

could have something to do with how

your grandmother was living while

she was carrying her.

Does this mean that the Darwinian

model of evolution is dead? Of course

it doesn’t, even t hough t here a re now

epigeneticists who refer to themselves

as neo-Lamarckians (see page 72).

Most of the time, eggs and sperm are

protected from epigenetic changes to

the environment, and relatively few

newly established modifications are

likely to ma ke it t h rough to t he next

Dr Nessa Carey reveals

how diet, lifestyle and the

environment affect your genes

How epigenetic modifications are passed on to our kids

HOW IT WORKS

EPIGENETICS

The latest discoveries and cutting-edge genetic

techniques being developed in labs around the world

Epigenetic

modifications

are also

found on the

histones’ tails

DNA wraps around

proteins called histones,

which cluster together

in groups of eight

Epigenetic modifications

can occur on a strand

of DNA as well as on

histone proteins

Each histone

has a tail

DNA is curled around proteins

called histones. When a cell receives

signals from the environment,

tiny chemical modifications are

made to the DNA and to the

histone proteins. These are called

epigenetic modifications, and

they regulate expression from

the DNA. There is a huge range of

different modifications, especially

to histone proteins, and they come

in a dizzying array of combinations,

creating vast flexibility in gene

expression. And because cells pass

on the same pattern of epigenetic

modifications to daughter cells

when they divide, these effects on

gene expression are maintained.

generation. Even when they do,

the modifications and the effects

they cause tend to die out within a

few generations.

Despite this, there is an increasing

a nd facile tendency to ‘bla me’

epigenetic inheritance for current

problems, especially with respect

to the human obesity epidemic.

Fascinating though this field is, it’s

not a get-out. The most important

things that are happening to your

health are happening here and now:

no one gains weight in 2015 just

because their grandad had a fondness

for doughnuts in the 1960s.

THE FUTURE OF