Homeotic Genes

‘Aristiotle said that  the ‘concept ‘ of a chicken is implict in an egg or that an acorn is ‘informed’ by the plan of an oak tree…The unity of life is an empirical fact. Erasmus Darwin was outrageously close to the mark: ‘One and the same kind of living filament has been the cause of all organic life…’ The secret of life is indeed a thread... Life is a slippery thing to define, but it consists of two very different skills: the ability to replicate, and the ability to create order. Living things produce approximate copies of themselves…Rabbits eat grass, transform it into rabbit flesh and somehow build bodies of order and complexity from the random chaos of the world…Rabbits build packets of order and complexity called bodies but at the cost of expending large amounts of energy. In Erwin Schrodinger’s phrase, living creatures ‘drink orderliness from the environment’. The key to both of these features of life is information…A rabbit’s egg carries the instructions for assembling a new rabbit…An adult rabbit, with its ability to both reproduce and metabolise, is prefigured and presupposed in its recipe. This is an idea that goes right back to Arisotle…The filament of DNA is information.’ Matt Ridley, Genome: The Autobiography of a Species in 23 Chapters, Fourth Estate, 2000

‘What is the source of the tension instigating next/ The rudimentary tail and gills, the cobweb of veins?/  What is the impetus slowly directing the hard-core/ current right up the scale to that one definite moment/ when a fold of cells quivers suddenly for the first time/ and someone says loudly “heart”…’ A.R. Ammons, Mechanism

‘The DNA in the cells of the early embryo replicates like mad…’ Ian Wilmut, Keith Campbell,  Colin Tudge, The Second Creation, Headline 2001

‘One of the most remarkable, beautiful and bizarre things that Mother Nature achieves without apparent difficulty is something for which we have no human analgoy at all: the development of the human body from an undifferentiated blob called a fertilised egg… Without the handrail of analogy, it is difficult even to understand Mother Nature’s feat. Something, somewhere must be imposing a pattern of increasing detail upon the egg as it grows and develops. There must be a plan. But unless we are to invoke divine intervention, that imposer of detail must be in the egg itself. And how can the egg make a pattern without starting with one... nature’s answer, as ever, turns out to be both simpler and much more easily understood - though the details are ferociously intricate. It all revolves around genes, which do indeed contain the plan in digital form. One large cluster of these developmental genes lies close to the middle of chromosome 12. The discovery of these genes and the elucidation of how they work is probably the greatest intellectual prize that modern genetics has won since the code itself was cracked. It was a discovery with two stunning and lucky surprises at its heart. As the fertilised egg grows into an embryo, at first it is an undifferentiatied blob. Then it gradually develops two asymmetries - a head - tale axis, and a front - back axis…the asymetries are almost certainly chemical. Each cell can, as it were, taste the soup inside itself, feed the information into its hand held GPS microcomputer and get out a reading: ‘you are in the rear half of the body, close to the underside’…But knowing where you are is just the beginning. Knowing what you have to do once you are there is a wholly different problem. Genes that control this process are known as ‘homeotic’ genes. For instance, our cell, on discovering where it is located, looks this location up in its guidebook and finds the instruction: ‘grow a wing’, or ‘start to become a kidney cell’…a guidebook is a handy analogy…because the great beauty of embryo development, the bit that humans find so hard to grasp, is that it is a totally decentralised process. Since every cell in the body carries a complete copy of the genome, no cell need wait for instructions from authority…’ Matt Ridley, Genome: The Autobiography of a Species in 23 Chapters, Fourth Estate, 2000

Organic and chemical orchestration

Organic and chemical orchestration of a script,

played by time and space, particular to here -

this space out of all others - among stars and green,

appearance of amoebae; fish, insects, lizards, birds,

mammals, the red marches of history, to converge

at this self-appointed building in life’s happening -

her holy stores stuffed with accelerating learning;

textures of beauty and cruelty - function, musical

unfolding of the embryo in the proper place,

the immaculate conditions for reproduction –

invisible flower-packed seed or warm, muddling,

tottering baby; fly cousins loving dirt and germs.

All patterns are laid in darkness, by some unknown

maker of garments - life robes, spectacular dresses -

subject to excitement of the identical beginnings,

which might bring sea urchin children or humans,

mouse or fly, from the same forming creature;

unspooling, releasing notes, appropriate, self-

tuned to the whole by some elaborate but simple

baton unseen, integral; part of the great principle.

If we had means to see cells immaculately making

the sculpture of the hand, wing, eye, as it happens,

what miracles might we not believe in, celebrate -

if this, the simplest of things, life, is so wonderful,

in conception, elucidation, practical illustration;

unfurling her astounding banners - so costumed

for the play, disguised in such colours, embroideries -

sackcloth and spines, cloaks of divergence; but united

beneath, in fundamental structure, same means

of production – a compulsive, propelling force

driving the common realisation of life among light -

starfish, human, sea urchin at first indistinguishable.

‘The result was the first of two almost incredible discoveries, which between them amount to one of the most wonderful additions to knowledge of the twentieth century. The scientitst found a cluster of eight homeotic genes lying together on the same chromosome, genes which became known as Hox genes… what was truly strange was the each of the eight genes affected a different part of the fly and they were lined up in the same order as the part of the fly they affected. The first gene affected the mouth, the second the eye…A second surprise was in store. In 1983 a group of scientists… discovered something common to all these homeotic genes. They all had the same ‘paragraph’ of text, 180 ‘letters’ long, within the gene – known as the homeobox. At first this seems irrelevant…Gehring’s colleague, Eddie de Robertis, acting on no more than a hunch, went fishing among the genes of frogs for a ‘paragraph’ that looked like the homeobox. He found it. When he looked in mice, there it was again; almost exactly the same 180-letter string. Not only that, the mouse turned out to have clusters of Hox genes…and, in the same way as the fruit fly, the genes in the clusters were laid our end-to-end…The discovery of mouse-fly homology was bizarre enough…What we doubly strange was the the mouse genes were recognisably the same genes as the fruit-fly genes…the similarity is still mind-blowing. It was so mind-blowing when it first came to light that few embryologists believed it. There was widespread scepticism…At the level of embryology we are glorified flies. Human beings have exactly the same Hox clusters as mice…the evolutionary implication is that we are descended from a common ancestor with flies…indeed, even more different creatures, such as sea urchins, are now known to use the same gene clusters…The incredible conservation of embryological genetics took everybody by surprise.’ Matt Ridley, Genome: The Autobiography of a Species in 23 Chapters, Fourth Estate, 2000

‘A 525,000-base region of the X chromosome consisting of 89% of repeated sequences is the most cluttered. At the other extreme are the 'HOX clusters' which regulate development. These contain less than 2% of repeated elements.’ Henry Gee, Nature

Hox Genes

Clusters of Hox genes, laid, in potential, correctly head to feet -

dressmaker nature preparing her pattern, invisible future-fabric;

firing the homeotic genes, chemical switches to spin the wing,

spine, feather, eye - exactly where nothing and message meet

in God and Nature’s physical and supernatural organic magic.

The same simple text - one hundred and eighty letters long -

homeobox’ in fish and man, lion and mouse; all just fantastic

variations, slow doodlings of millennia on the basic scheme -

chorus singing the same song; different poems recited in life’s

ancient language, repeating, elaborating – old story re-written

by everything alive; sea urchin child, human, sharing the same

words to create themselves - purpose and matter, form married.

Sometimes we have seen this common, implemental tongue

of life - in the eyes of our dog, gorillas looking from a cage,

prisoner hands curling bars; also in the human hands of mice.

Proved to us now our hands still hold the fin - wing and paw;

the communal template for life survives – shape, flesh, colour -

species, just intricate veils, fog; beautiful complexities of theme.

‘What is true of mice is just as true of people. Flies and people are just variations on a theme of how to build a body that was laid down by some worm-like creature in the Cambrian period. They still retain the same genes doing the same job….‘Indeed, so close are the similarities between genes that scientists…can knock out a gene in a fly…replace it with the equivalent gene from a human being and grow a normal fly. The technique is known as genetic rescue…Genes are just chunks of software that can run on any system; they use the same code and do the same jobs. Even after 530 million years of separation, our computer can recognise a fly’s software and vice-versa...’ Matt Ridley, Genome: The Autobiography of a Species in 23 Chapters, Fourth Estate, 2000

Spooling from the dark

Spooling from the dark, I came.

As first hot stars began to shine -

my high relations, I was imagined.

Evolving from random molecules,

until genes sparkled with messages

of me; in chemical engines, reading

Nature’s holy script - informing air -

Earth in the creation of my materials.

First water remembering in blood,

where sea creatures, lizards, birds

laid down their lives, learned bodies,  

that we might breathe this one day -

on a white shore, looking up to origin,

distance, mystery - light before stars -

where everything is illumined -

from where my pattern emerged.

‘..arthropods and vertebrates are upside-down versions of each other…Some time in the past they had a common ancestor…Pause for a second to pay homage to a great Frenchman, Etienne Geoffrey St Hilaire, who first guessed this fact in 1822 from observing the way embryos develop in different animals and from the fact that the central nervous system of an insect lies along its belly while that of a human being lies along its back. His bold conjecture was subjected to much ridicule in the intervening 175 years…but he was absolutely right.’ Matt Ridley, Genome: The Autobiography of a Species in 23 Chapters, Fourth Estate, 2000

In the womb is an unarticulated remembering -

memory of the wing, worm, living under water;

like this, in darkness, dimly aware of some place

else brighter; but not rocking, warm and peaceful

like here, where we will come with eyes shut -

so immersed, hearing some recognised sounds.


What spasm in the shoulderblade muscle

at a high cliff edge – head-spinning thrill

of flashing bright memory-wings an instant,

swan and eagle-like spread. White and gold

recitation of some poem in a forgotten language;

brilliant memory archived in life’s living library.

Science uncovers the miraculous

Science uncovers the miraculous;

she is her own species of light -

among fog, darkness and dour, wolf grey

of undisturbed loch. Her bright candles -

spotlights stutter, link, flame, blaze, die.

She is unlimited in creative speculation -

exploration, innovation, invention;

yet see her kneeling now - so low,

in presence of the Human Genome;

shuddering at first sight of such art,

still veiled in chemical code and letter -

the ancient, simple, pristine heart of life.


Gene sequences switch Off/On

Gene sequences switch Off/On,

as earless leaves hear Spring’s

shrill green soprano or Autumn’s low

gold baritone - winter’s deathly lyric -

tuned by silent mechanisms, as violins

give no physical clue to ethereal music.

Tree roots manufacturing bud-bombs;

exploding slowly, clenched lime fists,

relaxing into green summer poetry

of fluttery fingers recited into sky -

until timed autumnal conflagration,

detonated flames, but arsenal saved.

Complexity from Simplicity

We have revealed the magician’s trick;

complexity from simplicity - but why

remains the mystery. Why this happening

of embryology - making of organic matter

out of blank and scripted darkness;

response of life to such conditions.

We are the Master Print

We are the Master Print, uniquely doodled;

the Master Pattern, originally embroidered -

Master Song specially sung with new verses;

the Master Poem - spoken in our own words.

My body has heard the Word -

My body has heard the Word -

voice calling in unformed dark;

same throat calling among stars

and planets looking for homes -

it has found me - coming to reside

a little while, temporarily fulfilled.

‘Where do genomes come from? We actually have two genomes each! We get one copy of our genome from each of our parents. A sperm cell has only one copy of a genome, and an egg cell also only has only one copy. At the moment of fertilisation, the sperm cell and the egg cell join together to make a cell containing two genomes. The fertilized egg is like all the other cells in our body: it has two copies of the genome. These will act as a complete set of instructions to make a new human being!’

‘…most people tend to assume that a new individual is ‘conceived’ when sperm and egg meet to create a zygote. But in the zygote the male and female genomes remain separate until the zygote itself divides. Do two divided individuals form an ‘individual’?’ The Facts of Life Revisited, Ian Wilmut, The Second Creation, Headline, 2001

Not in charge

It is not my body. My name

is but loosely applied - yet I

feel fiercely ripe with identity.

I am not in charge of most

of what’s happening here -

am simply the host for life,

unfolding its coded patterns -

weaving, stitching, patching;

the unseen hand like a string

of lights, scatter of stars linking

arms - such eagerness knocking

my prisoning ribs, the squirming

fish in my warm stock bowl

already anxious - drowning

a little without air and light.

‘Multicellular creatures like oak trees and human beings produce specialist sex cells known as gametes – and again, two gametes must fuse to form just one new embryo. Sex, in short, is anti-replication. Replication implies that one individual divides to become two or more. But with sex, two combine into one.’ Ian Wilmut and Keith Campbell, The Second Creation, Headline, 2001

Mixing our Genomes

As our child grows, I see our genomes

writing him - now offering clues to us -

genetic principles. Eyes highly arched -

North Sea colours, with wave-tumbled

glass-green scribbles. Scottish skin,

that luminous skimmed-milk white,

rough straw hair of the bleached north -

witchy fingers. His father’s Cupid bow,

gorgeous girl’s eyelashes -

(sooty butterflies fluttering);

enviously fast metabolism -

but deleting his wonky toe,

shark-descended teeth -

mummy’s curious knees;

her slightly pocine, mushroom snitch…

Hurrah! Nature is definitely an artist.

Culture of four billion years

From us - you have taken the best

of all things. You have exulted us,

made us better, written us again;

more perfectly, more beautiful -

you have shown us what love means,

at last: a culture of four billion years.

Note from the author
exploring the project

    Gene Story
    Romantic Science
    Some Special Genes
        Homeotic Genes
        Embryo Story
        The Amazing Tale of
        Cell Division
        The ‘Selfish’ Gene
    X & Y

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