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By Jonathan Crowe

What links a queen honeybee to a particular group of four atoms (one carbon and three hydrogen atoms, to be precise)? The answer lies in the burgeoning field of epigenetics, which has revolutionized our understanding of how biological information is transmitted from one generation to the next.

The genetic information stored in our genome – the set of chromosomes that we inherit from our parents – directs the way in which we develop and behave. (We call the attributes and behaviours exhibited by an organism its ‘phenotype’.) Traditionally, the genetic information was thought to be encoded solely in the sequence of the four different chemical building blocks from which our DNA is constructed (that is, our genome sequence). If a DNA sequence changes, so the resulting phenotype changes too. (This is why identical twins, with genomes whose DNA sequences are identical, look the same, but other individuals, whose genomes comprise different DNA sequences, do not.) However, the field of epigenetics opens up a strong challenge to this traditional view of our DNA sequence being the sole dictator of phenotype.

So what actually is epigenetics? In broad terms, epigenetics refers to the way that the information carried in our genome – and the phenotype that results when this information is ‘deciphered’– can be modified not by changes in DNA sequence, but by chemical modifications either to the DNA itself, or to the special group of proteins called histones that associate with DNA in the cell. (It’s a bit like taking a book, with a story told in the author’s words, and adding notes on the page that alter how the story is interpreted by the next person to read it.)

But what has epigenetics to do with the group of four atoms, the one carbon and three hydrogen atoms mentioned at the start of this blog post? These four atoms can combine to form a methyl group – a central carbon atom, with three hydrogen atoms attached; the addition of methyl groups to both DNA and histone proteins in a process called methylation is a primary way in which epigenetic modification occurs. For example, the addition of a methyl group to one of the four chemical building blocks of DNA (called cytosine, C) either when it appears in the sequence CG (where G is the building block called guanine) or the sequence CNG (where N represents any of the four chemical building blocks of DNA) appears to result in that stretch of DNA being ‘switched off’. Consequently, the information stored in that stretch of DNA is not actively used by the cell; that stretch of DNA falls silent.

But what of our queen honeybee? Where does she fit into our story? A queen honeybee has an identical DNA sequence to her workers. Yet she bears some striking differences to them in terms of physical appearance and behavior (amongst other attributes). These differences are more than just skin-deep, however: the pattern of methylation between queen and worker larvae differs. Their genomes may be the same at the level of DNA sequence, but their different patterns of methylation direct different fates: the queen honeybee and her workers develop into quite distinct organisms.

Things take an interesting turn when we consider the cause of these different methylation patterns: the diets that the queen and workers experience during their development. The queen is fed on large quantities of royal jelly into adulthood, while worker larvae face a more meager feast, being switched to a diet of pollen and nectar early on. It is these diets that influence the way in which the queen and worker bees’ genes are switched on and off.

It is not just the queen honeybee whose genome is affected by the environment (in her case, diet). Mice exposed to certain chemicals during pregnancy have be

 




I recently read Naomi Shihab Nye's Honeybee, and I really enjoyed it. I admit that parts of it felt too preachy for me, and other parts a bit inaccessible. But so many poems from it really struck my heart. Here are just a few favorites out of the 80+ poems in this collection.

The United States Is Not the World

and this I was reminded of by
            mamas in silk saris
            grandpas in burgundy turbans,
                        smoky overcoats
            Sikh boys with powder-puff topknots
            braided girls munching Belgian chocolate
            and a gloomy little lad with a strange golden cone on his head

            Thank you, I said. O thank you Gate
                        D-4, Amsterdam to Delhi
            months of smug Americana dissolving
                        quickly
            as tiny white no-jetlag pills
                        on the tongue

--by Naomi Shihab Nye, all rights reserved

Don’t Say

God said.

You made it up

then put it in God’s pocket.

God may have thrown it out already.

--by Naomi Shihab Nye, all rights reserved

To One Now Grown

If we could start over, I would let you get dirtier.
Place your face in the food, it's okay.

In trade for great metaphors,
the ones you used to spout every minute,
I'd extend your bedtime,
be more patient with tantrums,
never answer urgency with urgency,
try to stay serene.

In one scene you are screaming
and I stop the car.
What do I do next?
I can't remember.
I have buried it in the drawer of small socks.

Give me the box of time.
Let's make it bigger.
It's all yours.

--by Naomi Shihab Nye, all rights reserved

Well, the entling apparently did NOT win a trip to J.K. Rowling and the Moonlight Signing at London’s Natural History Museum, on July 21st. There were ONLY 40,000 plus other entries. I note that a 17 year old girl in the area did get the call.

Hokey smokes, look at the line up B&N and Disney Publishing has put together for July 20 at Barnes & Noble Union Square in Manhattan!

Dave Barry (via video) and Ridley Pearson
Eoin Colfer (via video)
Rockstar Rick Riordan
Jonathan Stroud
Cinda Williams Chima (anybody read her books?)
Uber Narrator, Jim Dale

They will be webcasting the event.

Update: B&N is rescheduling the authors. They are now saying "each author will be individually rescheduled at a later date." -- from Mickey News

I have been listening to Book 6 so I will be ready. The entling has been reading them in reverse order, as is her tradition.