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Mutant DNA
Yearning to tinker with things better left alone? This faithful Technic structural model of DNA is tough enough and flexible enough to be uncoiled, unzipped, recoded, and put back like nothing ever happened. Just don't let it out of the house.
About this creation
Now on LEGOŽ Ideas here!

Please feel free to look over the images and skip the verbiage.

This MOC is a hands-on Technic structural model of a short segment of everybody's favorite polymer after ABS plastic -- deoxyribonucleic acid (DNA). The scale is roughly 6 x 1014 to 1.

Unlike the studded DNA models currently found on MOCpages, this Technic rendering is compact enough, tough enough, and flexible enough to be handled, uncoiled, unzipped, recoded, rezipped, and recoiled with little fuss.

Genetically modified LEGOŽ, anyone?





Like most of the body's DNA, this little DNA segment encodes an amino acid sequence. These coded sequences usually serve as blueprints for proteins, which typically contain thousands of amino acids chained end to end.

However, the body also finds use for chains of less than ~30 amino acids referred to as peptides. Endorphins (9-31 amino acids each) and the closely related endomorphins (all tetrapeptides of 4 amino acids each) are personal favorites.

The DNA segment modeled here encodes a made-up psychoactive tetrapeptide with endomorphin-like activity. It's released by the central nervous system only on exposure to LEGOŽ.

Individuals with this snippet of DNA in their genes are highly predisposed to LEGOŽ addiction.

On this page:


The structural model

Most of the DNA found in genetic material is double-stranded DNA (dsDNA), and that's what I've modeled here.





In dsDNA, two equal lengths of single-stranded DNA (ssDNA) are weakly bonded to and tightly wound around each another along the axis of a double helix. The real coiling is ~5 times tighter than shown here.



The ssDNA strands are better appreciated when the double helix is uncoiled and unzipped, as shown above.

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DNA modularity

The modular structure of dsDNA is well-suited to LEGOŽ modeling. Each constituent strand of ssDNA is a polymer (chain) of similar but not identical monomers (repeated units) known as nucleotides.

Each nucleotide consists of 3 strongly bonded subunits:
  • A phosphate group (PO4; hereafter, just "phosphate")
  • A 5-carbon sugar molecule known as 2-deoxyribose (hereafter, just "sugar") bonded to the phosphate
  • A nucleobase (aka "nitrogenous base", but hereafter, just "base") bonded to the sugar at ~90° to the phosphate.



In the model nucleotide above, the phosphate, sugar, and base subunits are represented by (i) black pin joiners, (ii) black #1 angled connectors, and (iii) white, orange, red, and yellow pin joiners, respectively.

Every nucleotide uses the same phosphate and sugar subunits. The bases, however, vary from one nucleotide to the next, and therein lies the genetic code.

The backbone of an ssDNA molecule, here modeled in black, is a strongly bonded chain of identical but alternating phosphates and sugars. The dsDNA double helix has 2 such backbones.





Each base subunit (colored pin joiner) in a strand of ssDNA forms 2 very different bonds. One is a strong covalent bond to a backbone sugar in its own strand, as shown above.

The other base bond is a much weaker hydrogen bond to a corresponding base on the other ssDNA strand of dsDNA, as shown below.



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Base pairs

The base-base hydrogen bonds are the only cross-links holding the 2 ssDNA strands of dsDNA together. The 2 bases involved in a particular cross-link are referred to as a base pair (bp).



The relative weakness of the base-base bonds allows the ssDNA strands to separate (unzip) temporarily for transcription and repair purposes.

This MOC contains 18 bp. The human genome contains some 6 billion bp packaged in 23 chromosome pairs. Each chromosome consists of a single dsDNA macromolecule encased in proteins.

The largest human chromosome (number 1) packs ~220 million bp into a coiled dsDNA length of 85 nanometers. That's 2.6 x 1013 bp/mm to my 4.3 x 10-2 bp/mm. At that rate, a LEGOŽ model of this one piece of chromosomal dsDNA would be over 5,000 km in length!

The model color-codes the 4 chemically distinct base subunits in DNA as follows: Adenosine (A), cytosine (C), guanine (G), and thymine (T).



For chemical reasons, adenosine cross-links only to thymine, and vice-versa. Adenosine and thymine are therefore complementary in that an adenosine or thymine found on one strand of ssDNA in a dsDNA molecule guarantees a thymine or adenosine, respectively, in the corresponding location on the other strand.

Cytosine and guanine are also complementary in this sense. Normal bases don't cross-link to themselves.

The sequence of bases in one of the strands of ssDNA in a dsDNA double helix serves as a "positive" image of the amino acid sequence of a particular protein or peptide.

Under these base-pairing rules, the other strand becomes a "negative" copy of that image. Hence, each strand encodes the same genetic information in inverse and redundant fashion.

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Genetic coding

Genetic information is encoded in the sequence of bases found along a strand of ssDNA. The negative strand is the one actually read during DNA transcription. The positive strand serves mainly as a scaffold, backup copy, and repair template for the negative strand.

The 4 DNA bases function as an alphabet of 4 letters used to form 3-letter words known as codons. Each codon specifies either (i) a specific amino acid to be added to a proptein or peptide in sequence, or (ii) a START or STOP command used to control transcription.



Hence, my 18 bp dsDNA snippet contains 6 codons. The farthest and nearest codons on the positive strand (the one on the right) are the START (ATG) and STOP (TGA) codons, respectively.

The 4 codons in between (CTG, GAC, GGG, GCT) specify a sequence of 4 amino acids (leucine, glutamic acid, glycine, alanine) to be polymerized into a tetrapeptide that spells "LEGA" in IUPAC amino acid symbols.

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A little accident at codon 4

Since the IUPAC didn't see fit to assign "O" to any normal amino acid, I had to take matters into my own hands to get the "LEGO" tetrapeptide I was after.

The first step was to arrange for that last codon to have a little accident.





Behold, a codon made entirely of the self-cross-linking 235U-bearing base godzillamine (Z) first extracted from a large Japanese lizard in the 1950s.

The codon ZZZ calls for offamine, an amino acid banished from proteins and peptides soon after life began for its nasty habit of falling off as soon as it was put on.

Having no need of an IUPAC symbol until now, I hereby assign offamine the symbol "O".

And there you have it: Mutant DNA bearing the codons CTG, GAC, GGG, ZZZ -- the recipe for the leucine, glutamic acid, glycine, offamine tetrapeptide that spells "LEGO".

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Design notes

The DNA models currently found on MOCpages are all studded table pieces not meant to be handled. The studded rendition by Vladimir van Hoek is truly spectacular.

I was after a different kind of DNA:
  • A faithful color-coded schematic structural model of dsDNA uncluttered enough to let the macromolecule's striking modularity and genetic coding shine through
  • A model able to hold a decent twist on its own
  • A model tough enough to be handled, uncoiled, unzipped into ssDNA strands, rezipped, and recoiled without serious damage.
This MOC fills the bill reasonably well.

However, it just can't match the tight coiling (~35°/bp) of the real dsDNA double helix. Given the constraints listed above and parts available, the best pitch I could muster was the ~7°/bp seen here. van Hoek's DNA model is much more realistic in this regard.



That's a a far cry from the real pitch, but at least it evokes a decent double helix without obscuring the base pair coding inside.

The simple pin joiner-friction pin construction was the best compromise I could find between flexibility and hold. It was also relatively inexpensive.

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Specifications


Overall dimensions (coiled):
464x64 mm (LxD)

Overall mass:
[] kg ([] lb), excluding stand

Scale:
~6 x 1014 to 1

Chemical name:
Double-stranded deoxyribonucleic acid (dsDNA)

Double helix radius:
32 mm

Total double helix twist:
165°

Double helix pitch:
7°/bp

Coiled nucleotide length:
23.2 mm/bp

Base pairs (nucleotides) per strand:
18

Coiled base pair density:
0.043 bp/mm

Codons per strand:
6

Encoded peptide type:
Endomorphin-like tetrapeptide

Encoded peptide length:
4 amino acids

Codons before mutation:
ATG, CTG, GAC, GGG, GCT, TGA

Original codon translation:

START-Leucine-Glutamic acid-Glycine-Alanine-STOP

Original peptide:
LEGA (IUPAC symbols)

Original peptide pharmacology:
Predisposition to LEGOŽ addiction

Codons after mutation:
ATG, CTG, GAC, GGG, ZZZ, TGA

Mutant codon translation:

START-Leucine-Glutamic acid-Glycine-Offamine-STOP

Mutant peptide:
LEGO (revised IUPAC symbols)

Mutant peptide pharmacology:
Lord only knows

Modified LEGOŽ parts:
None

Non-LEGOŽ parts:
None

Credits:

Original MOC





Comments

 I made it 
  February 7, 2017
Quoting Didier B Jeremy, this creation is absolutely brilliant ! How to teach/explain DNA with legos... This could and should be used by teacher to make this more interesting for students. Cheers, Didier
Very kind, Didier! It's definitely generated some interest from teachers who happen to have seen it in LEGO shows or on LEGO Ideas. Thought for sure it'd do reasonably well on the latter, but it ended up with only 127 votes.
 I like it 
  February 7, 2017
Jeremy, this creation is absolutely brilliant ! How to teach/explain DNA with legos... This could and should be used by teacher to make this more interesting for students. Cheers, Didier
 I made it 
  December 9, 2015
Quoting Tom Remy Hi Jeremy! I'm browsing through your Mocs when I find a moment, took the time to (partially) read the text and I think I found an error! :D The scale is 6x10^14:1 and not 1:6 x 10^14, that would be very very very very small ;-)
Thanks for looking through my MOCs, Tom. I know it's a big time commitment. All fixed.
 I made it 
  December 9, 2015
Quoting Tom Remy Hi Jeremy! I'm browsing through your Mocs when I find a moment, took the time to (partially) read the text and I think I found an error! :D The scale is 6x10^14:1 and not 1:6 x 10^14, that would be very very very very small ;-)
Thanks for catching that, Tom. I'll fix it today.
  December 9, 2015
Hi Jeremy! I'm browsing through your Mocs when I find a moment, took the time to (partially) read the text and I think I found an error! :D The scale is 6x10^14:1 and not 1:6 x 10^14, that would be very very very very small ;-)
 I made it 
  November 12, 2015
Quoting Geology Joe Wow! Amazing model, and a very informative and entertaining description! I may borrow this design idea for my classes...
Too kind, Joe. You're welcome to it.
 I like it 
  November 12, 2015
Wow! Amazing model, and a very informative and entertaining description! I may borrow this design idea for my classes...
 I made it 
  February 21, 2015
Now on LEGOŽ Ideas at http://ideas.lego.com/stream/project/link/17c5269d-f380-4be4-a245-fed95c15297a ! Your support would be greatly appreciated.
 I made it 
  February 16, 2015
Thanks to all for the kind words and likes. I really appreciate it.
 I like it 
  February 15, 2015
Ah, I see you have created the basic "building blocks" for life. Hahahahaha! Or wait, that's cells that are the basic building blocks. Whatever. :P Really excellent creation here! Love the nice color blend and of course the intricate structure itself is eye-catching. 5/5! :-)
 I like it 
  February 14, 2015
Great original idea. Again proof how Lego can unfold the misteries of Life as we know it!
 I like it 
  February 13, 2015
Simple yet elegant - very like the real thing, just bigger!
  February 13, 2015
Evolutionary! God Creates Man. Man Creates Lego. :-)
 I like it 
  February 13, 2015
Awesome, that's a really sleek molecule! At a loss of structural integrity, instead of technic pins, with a hose or flex-tube backbone you might be able to wind the coil a little tighter. Thanks for the comment! CAT-GCT-GTT-GAA TTC-U-AAT!!!
Jeremy McCreary
 I like it 
Matt Bace
  February 12, 2015
Pretty neat! It brings backs memories of having to read The Double Helix for freshman biology.
 I like it 
  February 12, 2015
Great Job Jeremy. I have seen this done with regular LEGO bricks, but never with Technic.
 I like it 
  February 12, 2015
Fantastic work on both the strands and the write up! Better than a textbook!
 I made it 
  February 12, 2015
Thanks to all for the likes and the very kind words. Added some new photos to bring out the curvature.
 I made it 
  February 12, 2015
Quoting matt rowntRee Awesome! Stuart Lucas should get a kick out of this one. Get a kick. GATACAC. Ha! Okay, it's a reach, but it did pop into my head as I typed it. Yeah, my own DNA is faulty, I know. XD Anyways, cool model, I wish science classes early on would have introduced this in Lego after all it is OUR building block. Great idea!
Matt, Wonderfully strange things are always popping into your head. Thanks for the support.
 I like it 
  February 12, 2015
great job!:D
 I like it 
  February 12, 2015
Excellent creation. The amount of informations is impressive, and the lego creation is well made as well. Keep bricking!
 I like it 
  February 12, 2015
Beautifully built! I love the curve
 I like it 
  February 12, 2015
Brilliant!
 I like it 
  February 12, 2015
An excellent and well built concept.
 I like it 
  February 12, 2015
Hats off to your idea. not only the MOC itself, but the divulgative purpose too deserves 5/5!
 I like it 
  February 12, 2015
Awesome! Stuart Lucas should get a kick out of this one. Get a kick. GATACAC. Ha! Okay, it's a reach, but it did pop into my head as I typed it. Yeah, my own DNA is faulty, I know. XD Anyways, cool model, I wish science classes early on would have introduced this in Lego after all it is OUR building block. Great idea!
 
By Jeremy McCreary
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