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Drosophila Drosophila melanogastermelanogaster

ENTHUSIAST’S MANUALENTHUSIAST’S MANUAL

Drosophi laDrosophi laMelanogasterMelanogasterEnthusiast ’Enthusiast ’ ssManualManual

written by Dr J R S Whittledesigned and illustrated by H A Barnett

Models covered:All models fitted with the 2nd and 3rd issuegenomes from 1999 to 2004

© Metamorphosis & Design Publishing 2004All rights reserved. No part of this book may be reproduced ortransmitted in any form or by any means, electronic ormechanical, including photocopying, recording or by anyinformation storage or retrieval system, without permission inwriting from the copyright holder.

Metamorphosis & Design PublishingSchool of Life SciencesUniversity of SussexFalmerBN1 9QGUnited Kingdom

Contents

Chapter Section Page

Introduction Acknowledgments 1About this manual 1Introduction to Drosophila Melanogaster 2Quick Reference data 3Tools and work facilities 4/5The Naming of Genes 6/7

1/ Body plan and parts Introduction 8/9

2/ The Head Introduction 11Problems with the existing model 12Modification options 13

3/ The Thorax Introduction 15Legs 16Antennapedia 16Notum 17WIngs 18/19

4/ The Abdomen Introduction 21Segments 22Important note 23

5/ Advanced Modifications The World is your Fruitfly 25Cations and caveats 26Tickling and grooming responses 27Advanced Strategies 28Homeotic Mutations 29Imaginal discs 29

Short Conclusion 31

Glossary of Terms 33

I n t r o d u c t i o n 1

The aim of this manual is to assist those owners of a stock of Drosophila melanogaster to get the bestout of their insect. By doing this work themselves, they will be able to spot minor faults and correctthem before they develop into serious defects requiring genetic modification of a fundamental nature.With familiarity, owners may be able to progress to customising their fruitfly to reflect their own lifestyle.

The manual is divided into chapters, and each chapter is divided into numbered sections, which areheaded in bold type. Throughout the manual there are illustrations showing the layout and design of thebodywork and external structures.

The operations described assume that a well-found genetic laboratory is available. Where special toolsand genotypes are essential, their source and use are specified.

When the left or right side of the insect is mentioned, to orientate yourself, imagine that you yourselfare the insect.

Acknowledgments

Thanks go to Edith M Wallace, the artist employed by Thomas Hunt Morgan between 1920 and 1940,who produced amazing line drawings of mutants with such great detail.

The Genome of Drosophila melanogaster by Dan L Lindsley and Georgianna G Zimm (AcademicPress, San Diego, 1992) from which these images were taken for modification.

To the open, friendly and supportive international community of Drosophila geneticists.

Flybase, a database of the Drosophila genomehttp://fly.ebi.ac.uk:7081/

Photographs by Heather Barnett, except on pages 17 and 29, by Robert Whittle

About this manual

D r o s o p h i l a M e l a n o g a s t e r E n t h u s i a s t s M a n u a l2

Introduction to Drosophila melanogaster

Drosophila melanogaster, the particular species of fruitfly which has become the focus ofcontemporary research in genetics and development, was first ‘domesticated’ in Columbia University,New York at the beginning of the 20th century. It was probably chosen because it was commonlyavailable, easy to culture on cheap media like bananas, and bred rapidly. In the ‘fly lab’ of Thomas HuntMorgan in Columbia, it was the experimental material from which pioneering and fundamental

knowledge of genetics was gained.Recognition of sex-chromosomeinheritance patterns, and the idea ofbeing able to construct genetic linkagegroups from recombination mappingall started there.

Its ‘virtues’ for genetic research wereunknown and could not have beenpart of the choice; indeed their virtuesbecame defined after the fact.Contrast that with the very deliberatechoices made more recently to initiategenetic analysis on the nematodeworm Caenorhabditis elegans and thezebrafish Danio reri. Valid and verifiedreasons were advanced for adoptingthese latter species as subjects forsuccessful genetic analysis.


Quick Reference Data

Capacities and settings:

Genome size ............................................................... 1.7 x 108 base pairsGene number .............................................................. 13,600 (being revised upwards)Length ......................................................................... 2400μMass ........................................................................... 0.8gmsBody height ................................................................ 900μGround clearance ....................................................... 400μLife cycle .................................................................... 10 days at 25C.

Culture conditionsThere are legion proven individual fuels,lubricants and construction materials available.We recommend those based upon maize flour,yeast and glucose because they support thereliable construction of new individual fruitflies.We are less prescriptive about the diet of thegeneticist.


Tools and work facilities

A selection of good laboratory protocols is a fundamental requirement for anyonecontemplating the modification of a fruitfly. To help the average owner to decide which genetictechnologies are needed to carry out the various modifications detailed in this style manual, wehave compiled lists of procedures and their sources.

Working facilitiesMaintained-temperature incubators arenecessary. Most geneticists prefer to work in anambient temperature between 19C and 22C, witha daylength of 16 hours with 8 hours darknessand low ambient noise.

Up to date informationIt would be a serious mistake for any enthusiastnot to take full advantage of the public domaininformation on the genetics, evolution anddevelopment of the fruitfly. Realising theexistence of this body of information is not the same as being able to grasp its detail, but we dorecommend that you visit http://flybase.net/ to be amazed.


Special toolsTo determine DNA sequences, you will require good extractionprocedures and a fast-turnaround sequencing service. To constructand introduce novel genetic material into the fruitfly genome, youwill need the facilities of a standard molecular biology laboratory.Generating new meiotic recombinants of a specified genotype isvery accessible to the enthusiast because it only requiresintelligence and logic rather than high-cost equipment.

Dissection toolsTo examine and to perturb the construction process as it isproceeding, you will need to practice dissecting larval stages, andthen learn to recognise internal structures called imaginal discs (seeChapter 5, page 29).

Basic toolsPaint brush or watchmakers forceps, a gooddissecting microscope with ‘cold’ light source, andpiped carbon dioxide supply for anaesthesia (of the flies).


Gene names


Each gene carries information for the constructionof a particular large molecule called a protein. Youmight have imagined that the best system to havebeen adopted might have been to name eachgene after what protein it ‘encoded’ or perhapswhat the gene ‘did’. However, many genes cameto the notice of geneticists one by one, and thenonly in a situation when they had failed to work.As a consequence, the resulting fruitfly carryingthis error had an imperfection in its appearance orfunction. The practice arose of naming each geneby describing some feature of what went wrongwhen the gene was not fully operational. Forexample, white was the name given to a genewhich when it failed, led to the fruitfly notaccumulating the correct pigments in its eyes(which are normally a dull brick red colour). Astime passed and more genes became known, thenaming process became more esoteric. There aregood reasons for this; to be unambiguouslyidentified, each gene requires a unique genesymbol derived from its name. A word label rather

than a numerical code makes it easier for you totalk about each gene. To illustrate this point, the following are all namesof fruitfly genes: oskar, sevenup, tudor, tinman,roundabout, caupolican, arrow, mirror, miranda.

Only the unwary fall into the trap ofthinking that genes are the agents ofdisaster and that organisms might bebetter off without genes. Do not join that club.

The naming of genes

SAFETY WARNINGThe naming practice for genes is a pitfall for the unwary. Please read the following safety warning so that you can avoid working in breach of conceptual clarity and rigour.

There are no grounds for the suggestion thatthis naming system was established so thatfruitfly geneticists could display their culturalheritage or establish an esoteric conceit thatwould later be locked into the language andconversations of other enthusiasts.


Head

Thorax

Abdomen

Chapter 1/ Body Plan and Parts

C h a p t e r 1 / B o d y P l a n a n d P a r t s 9

Standard Drosophila melanogaster body plan

D r o s o p h i l a M e l a n o g a s t e r E n t h u s i a s t s M a n u a l

C h a p t e r 2 / H e a d 11

Chapter 2/ Head

Eyes

Antennae

Proboscis

The fruitfly is a dipteran insect, and the construction of the head has avery complex evolutionary history. The current model does not easilyreveal the segmental origins of the structures. We do suggest that youregard the head as a sealed unit and that you do not attempt anydeconstruction or servicing of it yourself.

1. Unkempt bristles

As the accompanying figure shows, thehead is supplied with a large number ofmechanosensory organs on its surface.Despite a long-standing dialogue withthe manufacturers, no policy decisionhas ever been made to improve theunattractive and disordered layout ofthese ‘bristles’. It is argued that theprecise orientation of these bristles iscrucial to their function asmechanosensory detectors, but thatdoes seem a defeatist attitude for aninsect design studio.

2. Sexing flies

It has been widely reported that theefficient operation of the fruitflybrain is sensitive toincompatabilities in the peripheralsattached to it, and that upgrades inparticular peripherals will result inconsiderable downtime for yourinsect. For instance, a ‘female’brain does not work well in a ‘male’body. There are external structuraldifferences between the two sexes,and a host of physiologicaldistinctions, particularly in theabdomen relating to thereproductive sub-system. Beforeyou undertake sex-changetransformations, it will have to beaccepted that such products maybe reproductive failures.


Problems with the existing model

M F

?

C h a p t e r 2 / H e a d 13

One of the few accessible customising procedures immediately available to you is to alter thecolour of the two compound eyes in the head.

The standard model comes with specific quantities of two pigments, ommochromes andpteridines, already loaded into the eyes. It is possible to reset this programming so that therelative levels of these two components is altered or that one of the two pigments is omitted fromthe assembly process. As a result the compound eyes can have a colour that ranges in a spectrumfrom colourless (usually called white) to very pale lemon, through apricot to orange and bright red,and then to plum and brown shades. The naming of genes involved in the production of thesepigments follows the rule described earlier (see The naming of genes, page 7).

Despite evident successful progress in natural product biochemistry in the first half of the 20thcentury, the naming of the genes implicated in eye pigmentation is very much in the vernacular (forexample, burgundy, claret, karmoisin, scarlet, rosy, brown, sepia, vermilion, apricot).

Modification Options : Choice of eye colour

On the dorsal thorax, there is asuture that breaks the otherwiseair-smooth and beautifullypatterned array of sense organs

C h a p t e r 3 / T h o r a x 15

Chapter 3/ Thorax

Problems with the existing model

Less than elegant tarsalsegments that break the smoothoutline of the leg

An unnecessarily complicatedwing hinge structure


The Legs

The six-legged walking machine hasachieved enormous popularity ininsects. The process through whichappendages, including antennae as wellas wings and halteres, are built is anextremely elegant solution to a complexproblem in topology. This is more thancan be said for the appearance of thecompleted leg, which most enthusiastshave voted as the least attractive featureof their fruitfly.

At a late stage in its development, the 2-dimensional sheet of cells comprising each leg transformsinto a tube by eversion, formally similar to the way many telescopes can be unfolded. There is aclose spatial mapping (topological) relationship between the location of each cell in the flat sheetand its eventual position on the circumference and long axis of the everted leg.

AntennapediaA genetic modification that leads to atransformation of the tissue destined to becomethe antenna so that it instead forms a leg. Theresulting fruitflies therefore have eight legs, sixas normal on the thorax and two extending fromthe head. The ectopic legs do have connectionsto the brain and these flies show the proboscisextension reflex when sugar solution ispresented to the ‘head-legs’. Although this

transformation is fascinating, it has not becomepopular, and most enthusiasts have walkedaway from it.

Nasobemia was the name given to the genein which mutation causes a leg to develop in placeof the antennal segment. The name comes from aSwiss fairy story about the giant Nasobem whowalked on his nose. Subsequently this was shownto be part of the Antennapedia gene.

The Notum

The notum is the virtually flat skeletalplate that occupies the mid-lineposition on the middle segment of thethorax, between the two wings. It isbest viewed from above the fruitfly. Atfirst glance, there appears to be abewildering array of seeminglydisorganised bristles of various sizesdistributed over its surface.

Closer inspection of the notum, whichis possible without many workshopfacilities, will reveal that there is astereotypical pattern to these bristles.Furthermore, the larger bristles form atotally invariant array, and are asstriking a feature as the five digits on ahuman hand, though smaller.

Examination of this area of the thoraxin related insect species reveals thatthere are several components to thefruitfly bristle pattern and that it may bepossible to retrace the possibleancestry of this design. Now that it isbecoming possible to remove orexchange genes between differentspecies, features of this evolutionaryhistory model are being tested directly.


The Wings

The standard fruitfly is fitted with two fixed-geometry wings which are mirror-symmetric. Each wingis supplied with five longitudinal veins in a stereotypic pattern. The size and shape of each wing ina group of fruitflies related by direct ancestry are usually identical, and the invariance of thesefeatures speaks for the robust nature of the construction process.

Non-standard wings are available, reflectinggenetic differences inherited from the parentsof such individuals. Above are shown nine outof legion pattern changes that are availableupon demand.

(a) is a wing from the mutant Lyra, named after thatmusical instrument. This wing is clearly incompleteand looks as if parts have been cut off. (b) is a Lanceolate mutant wing. The overall shapeis changed but the components are all still present. (c) is a disrupted wing in which the vein pattern isdisturbed centrally and the overall outline has beenchanged. (d) lacks the posterior cross vein joining veins 4 and 5. The gene involved is called Confluens.

(e) is produced by a mutation in the Broad geneticcomplex. The wing is small and its shape has beenchanged. (f) is the result of a dominant mutation in the geneapterous. Complete loss of this function in the wingimaginal disc (see page 29) leads to fruitflieswithout any wings, as the gene name suggests. (g) shows a genetic failure in the genecrossveinless. (h) is the wing from a Dichaete mutant.

You can obtain such variants by requestingthem from stock centres as ‘readymades’ andthis is far easier than attempting to create themyourself as de novo genetic modifications, orby microsurgery or RNA interference, see p 19.



STOCKS

It is important to realise that if you set out tocustomise your fruitfly stock, then the easiestway is to set about it indirectly by altering thecomplement of genes in the fertilised egg. Eventhen, you rarely have to resort to directnanoengineering of any of the genes. You willfind it far more straightforward to collect anumber of fruitfly stocks, each of which isalready carrying one of the modifications thatyou require. Then all you need to do is become

a stockbreeder and build flies carrying thenecessary genetic modifications, and then letthe process of development run itself. Incomparison with assembling a microlite aircraftor replacing a heart valve, which you might wellhave done in the past, you will be using a farmore indirect or ‘hands-off’ approach. You willgradually become more skilled at setting upnovel genetic conditions for building a fruitfly,but in each case the construction proceedswithout you having to be there at the time.

1. Abolishing the instructions, or inactivationor removal of DNA sequences. In the trade,this is commonly called mutagenesis. Previouspractice has led to the accumulation of a largecollection of fruitfly stocks, each of which carriesand perpetuates a genetic defect in a knowngene. In the case of the examples illustrated,the criterion for saving the variant would havebeen that the wings were changed in some way.The majority of these can be ordered on line asreadymades at low cost. Attempting to combine the attributes of twoseparate variants in one individual fruitfly is anoption, but the outcome is unpredictable, unlessyou have full understanding of the constructionprogramme for the wing.

2. Upset at the point of delivery, or RNAInterference. A more recent technologicaldevelopment has been to offer a modification kitwhich allows you to ‘knock down’ thecontribution of any chosen gene or genes in realtime at the point of their operation. Realise thatif you follow this route, you do not make anychanges to the DNA so you would have torepeat this intervention in each successivegeneration in order to ensure a supply of yourchosen variant.

3. Re-writing part of the program, ortranscriptional modification. This dependsupon a deeper understanding of molecularconnectivity within the transcriptional apparatus,and would not be a recommended route for anenthusiast starting out on their own.

All three strategies could be pursued in theabsence of full technical support and know-how,and you may be pleasantly surprised, but thereis no guarantee of success, and you abdicateany design control. This approach is akin tochoosing your holiday destination by joining anunknown check-in queue at the airport, orpreparing to give a dinner party by shopping in asupermarket in total darkness.

Three complementary workshop strategies are available for the modification of wings to customise them.

21C h a p t e r 4 / A b d o m e n

Chapter 4/ Abdomen

The abdomen is the part of the fruitfly thatmost obviously reveals its segmentednature.

On the dorsal side, each segment has arelatively rigid exoskeletal plate called atergite, and these are connectedlongitudinally by a more flexible part. In thesame way as the other exoskeletalcomponents of the fruitfly that are mirror-imaged about the mid-line, each tergite isactually the product of two separate hemi-tergites which are constructed separatelyand then merged at the mid-line.

The registration at the mid-line is usuallyexcellent and well-engineered.


Segments

Although in this manual we are describingthe external body styling, there are alsoimportant differences under the surfacewithin each segment. Within each sex, theorder or array of abdominal segments isunique and largely invariant from model tomodel, provided that the constructionprocess has been correctly followed. Themost common aberrations of manufacturethat you may come across are the absenceof one hemi-tergite and the occasionalincorrect mid-line fusion (for example, thatthe left hemitergite 3 has fused to the righthemitergite 4). There is clearly somecommon denominator to the fusion processfor all tergites, and indeed all mid-linejunctions. These incorrect midline joiningsare usually evidence of traumas sufferedduring the assembly process.

The tergites, the dorsal exoskeletal plates ofthe abdomen, have a more complex three-dimensional shape and the anterior twotergites do not have the elegance orsimplicity of the more posterior plates. It isunclear whether this design solution reflectsa constraint linked to the ‘wasp waist’ ofinsects or whether our aesthetic sense ismore limited here.

C h a p t e r 4 / A b d o m e n 23

IMPORTANT NOTE

Other manuals have been known todescribe the construction of theexoskeleton of a fruitfly as as anassemblage of plates like that of aVolkswagen beetle, but in our view this isseriously misleading to the enthusiast.

It is not the case that the adult can easilybe taken apart and re-assembled in a neworder to make a different model, as canbe done with a Volkswagen.

To achieve such a metamorphosis, it isthe programming that has to be ‘re-written’. We conceed that both fruitfliesand Volkswagen beetles are mass-produced products but we think thatneither simile nor metaphor belong in aninstruction manual for engineeringpractice.

C h a p t e r 5 / A d v a n c e d M o d i f i c a t i o n s 25

CHOICES

This manual has introduced you to a varietyof basic operations in fruitfly construction.Once you have obtained a reasonablefacility in genetic manipulation, you are atliberty to pursue your own projects andinterests. The biotechnology industry hasadopted the fruitfly enthusiastically, so youwould be moving in a sophisticated society.We list a few proposals to show the possiblescope you have.

• A collection of live customised fruitfliescould be installed as an object d’art, usingCC digital TV to obtain images that can bestreamed onto the walls of the living room.

• A series of stocks with particular eyecolour variants could supplant the Pantone© set of standard colour matches used incolour image reprography.

• Because humans and fruitflies have manygenes that are identical or very closematches, fundamental aspects of humandevelopment can be analysed moreeffectively using fruitflies. For instance,genetic mimics of human genetic diseasescan be created in these insects.

Chapter 5/ Advanced modifications

The world is your fruitfly


CAUTIONS AND CAVEATS

There is now a considerable body ofbioengineering knowledge about theconstruction of a fruitfly.

Individual protein molecules are specifiedwithin the genome, and the behaviour ororganelles and cells depends upon thecomposition and the abundance of theseassemblies of different molecules. Identicaland similar arrays of molecules aredeployed during the construction process atdifferent times and in separate locations.Profiles of these molecular inventories arenow coming onto the market. At the time ofgoing to press, there still remain someuncertainties about the full inventory ofproteins that a fruitfly contains, or thosewhich have had a transient existence duringthe construction phase.

Another fundamental choice faces you now,whether to aim for a working model ormerely a static display. Your startingmaterial is a sophisticated machine alreadyoptimised, and it is a considerable challengeto make a modification on aesthetic groundsand simultaneously ensure that it is afunctional entity.

Integrated construction

The consequence of this ‘integratedconstruction’ is that any attempt to modifythe events involved in one particularprocess may have untoward andunexpected outcomes for other parts of thefly. The desired customising may beimpossible or be accompanied by anunacceptable ‘design change’ or malfunctionelsewhere in the animal body.

Until the complete programmingspecification for the fruitfly has beenanalysed and published, this uncertainty willalways accompany any attempts byenthusiasts to modify their fruitfly. Meetingand dealing with these problems willcontinue to provide the excitement forenthusiasts whilst simultaneously offeringchallenges for the developmental geneticist.

26


There is a useful test that you can apply toyour fruitfly. It will begin to reveal thesignificance of the larger bristles on thedorsal part of the thorax, and issimultaneously a test for functionality of thenervous system.

First, immobilise your fruitfly, using anarrangement that does not damage anythoracic structures. Observing the insectunder a dissecting microscope, stand thefruitfly on its legs and gently touch oneparticular large bristle on the thorax or onpart of the wing. Expect to see a groomingreflex in which an ipsilateral leg will be usedto ‘clean’ the region in the vicinity of thebristle that you touched. It should bepossible to map the relationships betweenindividual mechanosensors and specificmotor responses. This will tell yousomething about the neurol-muscle circuitry.You could regard these procedures asformally similar to the routines undertakenby the pilot of a plane before take-off.

If you first subvert the genotype of yourfruitfly, so that the pattern and number ofbristles is altered, you will then have theopportunity to investigate the extent to

which this neuro-muscular circuitry hasbeen altered. As you do this, you can againcontemplate the relationships between theexternal body form, its functionality, andaesthetic criteria.

Tickling: testing the grooming responses of your fruitfly

Stop-motion action of leg grooming after tickling

Action of head grooming after tickling

Action of abdomen grooming after tickling

Advanced strategies

Re-programming transcriptional activation


Once you have a basic grasp of the rules forconstructing a fruitfly, you may well wish toprogress further than minor customising ormerely cultivating pathologically abnormalindividuals. This section introduces you to slightlymore sophisticated strategies for geneticmodification that you can employ to create orengineer a fruitfly of novel appearance. Yourdegree of success will depend upon how wellyou can execute novel designs, using the‘genetic programming’ language used in buildinga fruitfly.

GAL4A prime tool of considerable power available toyou is the GAL4 transcriptional activationsystem, which allows you to re-specify the profileof activity of any particular gene. It has beenestablished that, for many genes, the preciselocation and timing of their transcription andtranslation is an important determinant in theprogramming. In other words, it is as crucial thatcertain genes are silent in particular groups ofcells as it is that they are active in other cells.The GAL4 system makes available to you eitherthe complete cis-activation signals from a knowngene, or a chosen sub-set of these regulators,that you can use to drive transcription of anothergene. You can uncouple these cis-activationcomplexes from their normal responders by DNAmanipulation, and use them to drive transcriptionof any other transcription unit or units that youchoose. Indeed, the target for activation could bea gene that does not exist in the fruitfly genome.

Many of these GAL4 constructs are available offthe shelf but you may still have to alter theiroutput for your own needs. Many cis-activationcomplexes respond to multiple and successivemolecular cues that trigger their activity, some ofwhich may subvert what you wish to achieve,

and in the limit they may block developmentalprogress through to the formation of the adult.

To guard against this possibility, you may wish toincorporate the GAL80 repressor in yourmolecular circuitry, to lockdown your chosentarget gene from activation, and then release thisrepression by transposon-mediated cis-FLIPrecombination at a chosen developmental stage.

PAX6The compatibility of genetic elements taken fromthe genomes of widely different species maysurprise you, but should also be anencouragement. For example, it has beendiscovered that the coding sequence of a genecalled PAX6 taken from the mouse genome willreplace a related fruitfly DNA sequence andfunction satisfactorily in the construction of afruitfly despite the two construction programmeshaving diverged from one another a long timeago. Because the protein coded by each genecan show very specific interactions with othermolecular species, the fact that the ‘mouse’ geneworks satisfactorily in the fruitfly tells you that allthe crucial molecular recognition eventsthemselves could not have changed significantlybetween fruitfly and mouse, despite thedissimilarity of these two products. The longevityof this programming language contrastssignificantly with the transient nature ofprogramming languages used for wordprocessing, including the one used in writingthis manual.

WarningBefore you commence any of theseoperations, you must file a hazard document,estimating the risks involved, because you willbe working with genetically modified animals.

28

Homeotic mutations

The transformations that are most striking andwhich all enthusiasts read about from the outsetare those in which entire body parts orsegments are replaced by other structures orappear in foreign locations. The classictransformations are those resulting frommalfunction in the gene clusters called theBithorax and Antennapedia complexes (anexample is shown on page 16).

It has long been suggested that for a singlegenetic change to cause such a globalsubstitution, like the appearance of an extra pairof wings in place of the balancing organs in

thoracic segment three, that genes must beinvolved at a high level in the hierarchy ofdevelopmental decisions. This conclusion doesassume that the parallel between decision-making hierarchies constructed by humanbeings and fruitfly developmental ‘programming’is a good one.

Moreover, the temptation of enthusiasts toincorporate these mutations in their customisingchoices commonly leads to disappointment. Itmay be impossible to construct the imaginedfruitfly because some aspect of the‘programming’ cannot be achieved at the cellularor molecular level. The only solution would be towork in virtual reality using image manipulationsoftware.

Imaginal discs: an opportunityfor micro-surgery

Each of the segmental components of a fruitfly,the legs, the wings, or the antenna for example,has a modular origin. Inside the larva can befound coherent groups of cells each of which isdestined to form one of the segmentalstructures. These cell groups are called imaginaldiscs. You can verify the ‘destiny’ or the ‘fate’ ofeach of these imaginal discs as follows. Dissecta chosen disc from one larva and transplant itinto another larva. You will discover that thelarva become a fruitfly with one extra set ofsegmental structures. For example, choosing adisc of a particular size and location will giveyou a fly with one complete extra wing.Unfortunately this extra structure is not usuallylocated on the surface of the fruitfly but is foundcrumpled up inside the abdominal cavity.Nevertheless, using this successfultransplantation procedure will give you accessto a host of ‘hands-on’ microsurgicalpossibilities, and it is the exception to the morepervasive ‘hands-off’ approach of using ‘geneticprogramming’ to customise your fruitfly.


Conclusion 31

A SHORT CONCLUSION

We hope that this handbook will have provided many opportunities for you to enhance thevalue of your own stocks of the fruitfly for your own individual interests. It may be sufficientfor you to have been able to create and perpetuate heritable variants, or to have reached aposition of knowledge where you can enjoy reading about the history of genetics.

Alternatively, you may wish to join the aficionados and to display and exchange yourfavourite strains at meetings. Do remember that if you are holding genetically modifiedstocks, then in most countries you will be subject to legislation about the containmentarrangements for your collection.

Finally, and most fundamentally, this experience may have given you the impetus tocontemplate joining the community of geneticists who live to reveal and understand theseamazing machines

Glossary 33

Aesthetic senseAn ability to judge properties and attributes of objects and events based upon criteria thatextend beyond mere functionality

Check-in queueA period for quiet reflection prior to flying

GAL4 transcriptional activation systemA two-component system of DNA sequences derived from the yeast genome, that can beused to create novel molecular connectivity in relation to gene expression

Heart valve replacementAn example of a common DIY activity in the developed world

Imaginal discThe name given to a closed sac of epithelial cells found within a larva and which normallygive rise to a given external body part, e.g. a leg

NotumThe name of the large mid-line dorsal thoracic plate lying between the wings

MutationA heritable change in the polymer DNA. There is a dispute between those who restrict thisdefinition to changes that can be detected only from the consequence of the change inDNA sequence, and those who regard every heritable change in DNA as a mutation

ReadymadeSomething you found earlier in a finished form

RNAA polymer made by copying from a DNA polymer but using slightly different componentsthan are used in the replication of DNA

TranscriptionCopying of the nucleotide sequence in the polymer DNA into a second polymer called RNA

Glossary of terms

Metamorphosis & Design Science Manuals are written with the home biologist in mindwho may not have the luxury of a well equipped laboratory to hand. Each manualcovers a specific make and model, with all aspects thoroughly researched by theauthor.

Each manual presents aspects of dismantling, modifying and breeding your organismto help achieve results which are both highly functional and aesthetically pleasing.

What the press say...

“These are really worthwhile manuals which can save you a lot of money” Autofly

“Metamorphosis Manuals are outstanding for giving the learner biologist an easy tofollow guide to doing most any type of genetic alteration on his or her organism” Biology Weekly

“...written for the intelligent owner who wants to understand the construction andworking of his fruitfly, and who is not afraid to pick up a scalpel and dismantle it” New Geneticist

“These authentic manuals are actually written from practical experience...”The Fruitfly Review

“Beginners and experts should find it equally useful, overall a mine of information.”The Old Scientist

“For the home geneticist Metamorphosis Enthusiast’s manuals give easy to followinstructions” Home Genetics Monthly

“Every conceivable aspect is covered down to the minutest genetic function... aninvaluable asset.” Popular Drosophilist

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