DNA mobile

This pattern is for a mobile containing a DNA helix along with the 4 bases that make up DNA. It also contains the pattern to make Uracil (a base-like molecule found in RNA). 

DNA carries the genetic information that codes for all of the proteins that make up your body and allow it to function. The DNA model in the centre is approximately to scale, with a scale factor of 3x10^7. I've also included a lot of information on the science behind DNA intermixed with the pattern if you're interested.

Difficulty: 

Easy - medium

You will need:

• A 2mm crochet hook
• Dk yarn in purple, yellow, turquoise, dark pink, light pink, black, dark blue, and a scrap of white (although you're free to choose whatever colours do want for the base pairs)
• An embroidery hoop
• Craft wire
• Black yarn or crochet cotton for the embroidery, I used black #10 crochet cotton (you could use embroidery thread, but you would need to use a full strand so it would work out pretty expensive)
• Toy stuffing
• A darning needle
• A pair of scissors

Note:

• 'sc12' means 'sc in each of the next 12sts'
• 'fasten off neatly' refers to a special way of fastening off which is neater and makes it easier to see where you should be crocheting on the next round (also known as invisible fastening off). This involves pulling up your yarn through your stitch, threading the yarn underneath the second stitch from where you pulled your yarn up, then threading your yarn back through the top of this stitch and down through the back of the work. There is a very helpful site that explains it clearly found here. This is optional,but I find it makes the overall finish nicer.

So what is DNA?

DNA consists of 3 types of molecules: phosphate groups, a sugar called deoxyribose, and organic bases, which are what codes for all the proteins (see protein patterns) that make you up. These organic bases come in 4 different types, known as Cytosine, Adenine, Guanine, and Thymine, often referred to simply as C, A, G, and T respectively. 

These pair up within the structure of the DNA, with cytosine bonding with guanine, and adenine bonding with thymine. This is what ensures that DNA replication occurs correctly; if there is a C base on one DNA strand (see DNA helix pattern for more info on the structure of DNA), then there must be a G base on the other strand.

Part 1: The DNA bases

For Guanine:
Make all sections using turquoise yarn
For the smaller section (make 2):
Make a magic loop with 5sc
Round 1: make 2sc in each st (10sc)
Round 2: (sc, make 2sc in the next st) 5 times (15sc)
Round 3: (sc2, make 2sc in the next st) 5 times (20sc)
Round 4: (sc3, make 2sc in the next st) 5 times (25sc)
Round 5: sc5, ch6,  sc in the 2nd chain st from hook, sc in the next 4 chain sts, then sc in the same st as the one you crocheted in before you made the ch6, (sc4, make 2sc in the next st) 4 times
Round 6: sc4,  sc2tog between the next st and the back loop of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back of the last chain st. Make 2sc in the next st, sc3, sc2tog, (sc5, make 2sc in the next st) 4 times
Round 7: sc4, sc2tog, sc3, make 2sc in the next st, slip5, sc2tog, sc5, make 2sc in the next st (sc6, make 2sc in the next st) twice, sc7
Fasten off neatly

For the front:

Make a magic loop with 6sc

Round 1: make 2sc in each st (12sc)

Round 2: (sc in the first st, make 2sc in the next st) 6 times to end (18sc)

Round 3: (sc in the first 2 sts, make 2sc in the next st) 6 times to end. ch1, turn (24sc)
Round 4: (sc in the first 3 sts, make 2sc in the next st) 6 times to end (30sc)

Round 5: sc4, make 2sc in the next st, (sc5, ch6,  sc in the 2nd chain st from hook, sc in the next 4 chain sts, then sc in the same st as the one you crocheted in before you made the ch6) twice, sc5,  ch11, sc in the 2nd loop from hook, sc in the next 4 chain sts, ch6, sc in the 2nd loop from hook, sc in the next 4 chain sts, sc in the next 5 chain sts of the ch11 section, then sc in the same st as the one you crocheted in before you made the ch11, (sc4, make 2sc in the next st) twice
Round 6: sc5, make 2sc in the next st, (sc4,  sc2tog between the next st and the back loop of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back of the last chain st. Make 2sc in the next st, sc3, sc2tog) twice, sc4, sc2tog between the next st and the back of the next chain st, sc in the back loop of the next 3 chain sts, sc2tog between the back loop of the next 2 chain sts, sc in the back loop of the next 3 chain sts. Make 2sc in the back of the last chain st, then make 2sc in the next st. Sc in the next 3 sts, sc2tog between the next st and the back of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back loop of the last chain st. Make 2sc in the next st, sc3, sc2tog, sc3, sc2tog, (sc5, make sc in the next st) twice
Round 7: sc6, make 2sc in the next st, sc4, sc2tog, sc3, make 2sc in the next st, slip5, sc2tog, sc3, sc2tog, sc3, make 2sc in the next st, slip5, sc2tog, sc3, sc2tog, sc2, sc2tog, sc3, make 2sc in the next st, slip6, sc4, make 2sc in the next st, slip9, sc2tog, sc5, make 2sc in the next st, sc6, make 2sc in the next st
Fasten off neatly

For the back:

Make a magic loop with 6sc

Round 1: make 2sc in each st (12sc)

Round 2: (sc in the first st, make 2sc in the next st) 6 times to end (18sc)

Round 3: (sc in the first 2 sts, make 2sc in the next st) 6 times to end. ch1, turn (24sc)
Round 4: (sc in the first 3 sts, make 2sc in the next st) 6 times to end (30sc)

Round 5: sc5, ch11, sc in the 2nd loop from hook, sc in the next 4 chain sts, ch6, sc in the 2nd loop from hook, sc in the next 4 chain sts, sc in the next 5 chain sts of the ch11 section, (sc5, ch6,  sc in the 2nd chain st from hook, sc in the next 4 chain sts, then sc in the same st as the one you crocheted in before you made the ch6) twice
Round 6: (sc4, make 2sc in the next st) 3 times, sc4, sc2tog between the next st and the back of the next chain st, sc in the back loop of the next 3 chain sts, sc2tog between the back loop of the next 2 chain sts, sc in the back loop of the next 3 chain sts. Make 2sc in the back of the last chain st, then make 2sc in the next st. Sc in the next 3 sts, sc2tog between the next st and the back of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back loop of the last chain st. Make 2sc in the next st, sc3, sc2tog, sc3, sc2tog, (sc4,  sc2tog between the next st and the back loop of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back of the last chain st. Make 2sc in the next st, sc3, sc2tog) twice, (sc5, make 2sc in the next st) 3 times
Round 7: sc4, sc2tog, sc2, sc2tog, sc3, make 2sc in the next st, slip6, sc4, make 2sc in the next st, slip9, sc2tog, (sc3, sc2tog, sc3, make 2sc in the next st, slip5, sc2tog) twice, (sc5, make 2sc in the next st), sc6
Fasten off neatly

Place the front section next to one of the smaller sections, as shown in the first photo, and sew them together. Do the same for the back section, but make sure that the sections are lines up as shown in the third photo before you sew them together (so that they are the mirror image of the front).

After this you will need to embroider the chemical symbols onto each of the sections of crochet, as shown below (this shows the front section, you should embroider the reverse symbols onto the back section). The structure of each of the bases is also given at the start of this pattern as an extra reference point. Note that for bases G and A this structure shows the BACK of the the bases (this is important to allow them to pair up correctly)

 

I made each of the long straight sections representing the bonds by making a long strand from the start of the bond to the end, then making a few very small stitches along its length to secure it in place. This is demonstrated in the photos below.

You should also embroider the letter 'G' onto the back section.

For the eyes (make 2):
With black ch3
Round 1: make 2sc in the 2nd loop from hook, then make 3sc in the first chain st you made. Make 2sc into the back loop of the first chain st you crocheted into. (8sc)
Fasten off

Use white embroidery thread to embroider highlights onto the eyes, then sew them to the head. I found that the effect was better if you used the 'wrong side' of the crochet to face outwards. After you've done this embroider a mouth onto your base.

Sew the front and back sections of the head together , stuffing as you do so. Sew them together using a close backstitch (or running stitch if you prefer) so that you keep the ridge on the outside of the crochet.

Fun fact 1:
Typing at 60 words per minute for 8 hours a day it would take 50 years to type the entire human genome.

For Adenine:
Use yellow yarn throughout
For the small section (make 2):
Make a magic loop with 5sc
Round 1: make 2sc in each st (10sc)
Round 2: (sc, make 2sc in the next st) 5 times (15sc)
Round 3: (sc2, make 2sc in the next st) 5 times (20sc)
Round 4: (sc3, make 2sc in the next st) 5 times (25sc)
Round 5: sc5, ch6,  sc in the 2nd chain st from hook, sc in the next 4 chain sts, then sc in the same st as the one you crocheted in before you made the ch6, (sc4, make 2sc in the next st) 4 times
Round 6: sc4,  sc2tog between the next st and the back loop of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back of the last chain st. Make 2sc in the next st, sc3, sc2tog, (sc5, make 2sc in the next st) 4 times
Round 7: sc4, sc2tog, sc3, make 2sc in the next st, slip5, sc2tog, sc5, make 2sc in the next st (sc6, make 2sc in the next st) 3 times, sc7
Fasten off neatly

For the larger section (make 2):

Make a magic loop with 6sc

Round 1: make 2sc in each st (12sc)

Round 2: (sc in the first st, make 2sc in the next st) 6 times to end (18sc)

Round 3: (sc in the first 2 sts, make 2sc in the next st) 6 times to end. ch1, turn (24sc)
Round 4: (sc in the first 3 sts, make 2sc in the next st) 6 times to end (30sc)

Round 5: sc5, ch11, sc in the 2nd loop from hook, sc in the next 4 chain sts, ch6, sc in the 2nd loop from hook, sc in the next 4 chain sts, sc in the next 5 chain sts of the ch11 section, then sc in the same st as the one you crocheted in before you made the ch11, (sc4, make 2sc in the next st) 5 times
Round 6: sc4, sc2tog between the next st and the back of the next chain st, sc in the back loop of the next 3 chain sts, sc2tog between the back loop of the next 2 chain sts, sc in the back loop of the next 3 chain sts. Make 2sc in the back of the last chain st, then make 2sc in the next st. Sc in the next 3 sts, sc2tog between the next st and the back of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back loop of the last chain st. Make 2sc in the next st, sc3, sc2tog, sc3, sc2tog, (sc5, make 2sc in the next st) 5 times
Round 7: sc4, sc2tog, sc2, sc2tog, sc3, make 2sc in the next st, slip6, sc4, make 2sc in the next st, slip9, sc2tog, (sc6, make 2sc in the next st) 3 times, sc7
Fasten off neatly

Once again you will need to sew each of the small sections to the larger sections, as shown below (this shows the front section: the back will be essentially the same but with the smaller section on the left and the larger section on the right)

You now need to embroider the chemical symbols in place. (It may be easier to use the image at the top of this pattern for the reference, since the photo below isn't ideal for showing whats going on.)

You should sew a letter 'A' onto the back section, similarly to how you did for guanine.

For the eyes (make 2):
With black ch3
Round 1: make 2sc in the 2nd loop from hook, then make 3sc in the first chain st you made. Make 2sc into the back loop of the first chain st you crocheted into.
Fasten off

Use white embroidery thread to embroider highlights onto the eyes, then sew them to the head, as you have did for guanine. Sew a smile onto the face.

You will then need to sew the front and back sections together, stuffing firmly.


Fun fact 2:
Every human shares 99.9% of their DNA with every other human


How do the bases know who they should pair up with?
The pairing of the bases occurs due to attractions called hydrogen bonds that occur between the bases. Essentially the hydrogen atoms on the outside of one base are attracted to the oxygen/ nitrogen atoms on the outside of the base its paired with. Cytosine and Guanine can form 3 of these bonds between each other, whilst  Adenine and Thymine can only form two. This is one factor that ensures they bond correctly.
Another factor is the shape the bases form when bonded together. As you may have noticed, the bases come in 2 different sizes. The smaller ones, Cytosine and Thymine, are known as pyrimidines, whereas Guanine and Adenine are classes as purines. The bonding of one pyrimidine with one purine endures that the overall structure formed has a very similar shape (as you should be able to see in the image below). This allows them to fit tightly together within the DNA strand. Any other bonding would not fit nicely within the DNA helix, meaning that it would be unstable, and would inevitably be ripped apart.

Additionally, this shape is able to fit neatly into the active site of the enzyme that creates DNA, known as DNA polymerase. (see enzyme pattern and possibly a pattern on DNA structure)

For Cytosine:

Use purple yarn throughout

For the front:

Make a magic loop with 6sc

Round 1: make 2sc in each st (12sc)

Round 2: (sc in the first st, make 2sc in the next st) 6 times to end (18sc)

Round 3: (sc in the first 2 sts, make 2sc in the next st) 6 times to end. ch1, turn (24sc)
Round 4: (sc in the first 3 sts, make 2sc in the next st) 6 times to end (30sc)

Round 5: sc5, ch11, sc in the 2nd loop from hook, sc in the next 4 chain sts, ch6, sc in the 2nd loop from hook, sc in the next 4 chain sts, sc in the next 5 chain sts of the ch11 section, then sc in the same st as the one you crocheted in before you made the ch11.(Sc4, make 2sc in the next st) twice, (sc5, ch6, sc in the 2nd chain st from hook, sc in the next 4 chain sts, then sc in the same st as the one you crocheted in before you made the ch6) twice, sc4, make 2sc in the next st
Round 6: sc4, sc2tog between the next st and the back of the next chain st, sc in the back loop of the next 3 chain sts, sc2tog between the back loop of the next 2 chain sts, sc in the back loop of the next 3 chain sts. Make 2sc in the back of the last chain st, then make 2sc in the next st (the first one you made when crocheting into the chain sts of the previous round). Sc in the next 3 sts, sc2tog between the next st and the back of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back loop of the last chain st. Make 2sc in the next st, sc3, sc2tog, sc3, sc2tog, sc5, make 2sc in the next st, sc5, make 2sc in the next st, (sc4, sc2tog between the next st and the back loop of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back of the last chain st. Make 2sc in the next st, sc3, sc2tog) twice, sc5, make 2sc in the next st
Round 7: sc4, sc2tog, sc2, sc2tog, sc3, make 2sc in the next st, slip6, sc4, make 2sc in the next st, slip9, sc2tog, sc5, make 2sc in the next st, sc6, make 2sc in the next st, sc4, sc2tog, sc3, make 2sc in the next st, slip5, sc2tog, sc3,sc2tog, sc3, make 2sc in the next st, slip5, sc2tog, sc5, make 2sc in the following st, slip1
Fasten off neatly

For the back:

Make a magic loop with 6sc

Round 1: make 2sc in each st (12sc)

Round 2: (sc in the first st, make 2sc in the next st) 6 times to end (18sc)

Round 3: (sc in the first 2 sts, make 2sc in the next st) 6 times to end. ch1, turn (24sc)
Round 4: (sc in the first 3 sts, make 2sc in the next st) 6 times to end (30sc)

Round 5: sc5, ch11, sc in the 2nd loop from hook, sc in the next 4 chain sts, ch6, sc in the 2nd loop from hook, sc in the next 4 chain sts, sc in the next 5 chain sts of the ch11 section, then sc in the same st as the one you crocheted in before you made the ch11. sc4,  make 2sc in the next st,  (sc5, ch6, sc in the 2nd chain st from hook, sc in the next 4 chain sts, then sc in the same st as the one you crocheted in before you made the ch6) twice, (sc4, make 2sc in the next st) twice
Round 6: sc4, sc2tog between the next st and the back of the next chain st, sc in the back loop of the next 3 chain sts, sc2tog between the back loop of the next 2 chain sts, sc in the back loop of the next 3 chain sts. Make 2sc in the back of the last chain st, then make 2sc in the next st. Sc in the next 3 sts, sc2tog between the next st and the back of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back loop of the last chain st. Make 2sc in the next st, sc3, sc2tog, sc3, sc2tog, sc5, make 2sc in the next st, (sc4, sc2tog between the next st and the back loop of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back of the last chain st. Make 2sc in the next st, sc3, sc2tog) twice, (sc5, make 2sc in the next st) twice
Round 7: sc4, sc2tog, sc2, sc2tog, sc3, make 2sc in the next st, slip6, sc4, make 2sc in the next st, slip9, sc2tog sc5, make 2sc in the next st, sc4, sc2tog, sc3, make 2sc in the next st, slip5, sc2tog, sc3, sc2tog, sc3, make 2sc in the next st, slip5, sc2tog, (sc5, make 2sc in the next st) twice
Fasten off neatly

Embroider the chemical symbols onto each of the sections of crochet, as you have done for the previous bases, following the embroidery on the crochet below (which, once again, shows the front section of the crochet). You should also embroider the letter 'C' onto the back section, as shown below in the 2nd photo.

For the eyes (Make 2):
With black ch3
Round 1: make 2sc in the 2nd loop from hook, then make 3sc in the first chain st you made. Make 2sc into the back loop of the first chain st you crocheted into.
Fasten off

Use white embroidery thread to embroider highlights onto the eyes, then sew them to the head, as you have done for the previous bases


Sew the front and back sections of the bases together.

 

Fun fact 3:
Despite being much simpler organisms than humans, the gene of the aomeba is 200 times greater!

For Thymine:
Use dark pink yarn throughout
For the front and back (make 2):

Make a magic loop with 6sc

Round 1: make 2sc in each st (12sc)

Round 2: (sc in the first st, make 2sc in the next st) 6 times to end (18sc)

Round 3: (sc in the first 2 sts, make 2sc in the next st) 6 times to end. ch1, turn (24sc)
Round 4: (sc in the first 3 sts, make 2sc in the next st) 6 times to end (30sc)

Round 5: (sc5, ch6,  sc in the 2nd chain st from hook, sc in the next 4 chain sts, then sc in the same st as the one you crocheted in before you made the ch6) 5 times, sc4, make 2sc in the last st
Round 6: (sc4,  sc2tog between the next st and the back loop of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back of the last chain st. Make 2sc in the next st, sc3, sc2tog) 5 times, sc5, make 2sc in the last st
Round 7: sc4, sc2tog, sc3, make 2sc in the next st, slip5, sc2tog, (sc3, sc2tog, sc3, make 2sc in the next st, slip5, sc2tog) 4 times, sc5, make 2sc in the last st
Fasten off neatly

You now need to sew the chemical symbols onto the bases, as you did for the previous bases. The structure of thymine is shown below, (and can once again be found at the start of this pattern if you are struggling to see it properly). Once again you should sew the reverse of this structure onto the back of the base, and sew a 'T' into the centre, as shown below.


For the eyes (Make 2):
With black ch3
Round 1: make 2sc in the 2nd loop from hook, then make 3sc in the first chain st you made. Make 2sc into the back loop of the first chain st you crocheted into.
Fasten off

Embroider highlights onto these and sew them onto the face, as you did for cytosine. Embroider the mouth in place underneath, then sew the front and back sections together, stuffing firmly as you do so.

But wait - that's not all the possible bases
A similar molecule to our DNA is RNA. This is a single-stranded molecule whose strands differ in two ways to those of DNA: firstly the sugar in the structure is ribose, not deoxyribose, but also because the base Thymine is replaced with a slightly different base known as Uracil, the pattern for which is given below.


For Uracil:
Use light pink yarn throughout
For the front and back (make 2):

Make a magic loop with 6sc

Round 1: make 2sc in each st (12sc)

Round 2: (sc in the first st, make 2sc in the next st) 6 times to end (18sc)

Round 3: (sc in the first 2 sts, make 2sc in the next st) 6 times to end. ch1, turn (24sc)
Round 4: (sc in the first 3 sts, make 2sc in the next st) 6 times to end (30sc)

Round 5: (sc5, ch6,  sc in the 2nd chain st from hook, sc in the next 4 chain sts, then sc in the same st as the one you crocheted in before you made the ch6) 4 times, (sc4, make 2sc in the last st) twice
Round 6: (sc4,  sc2tog between the next st and the back loop of the next chain st, sc in the back loop of the next 3 chain sts, make 2sc in the back of the last chain st. Make 2sc in the next st, sc3, sc2tog) 4 times, (sc5, make 2sc in the last st) twice
Round 7: sc4, sc2tog, sc3, make 2sc in the next st, slip5, sc2tog, (sc3, sc2tog, sc3, make 2sc in the next st, slip5, sc2tog) 3 times, (sc5, make 2sc in the last st) twice
Fasten off neatly

You now need to sew the chemical symbols onto the bases. These are exactly the same as for Thymine, but without the single protruding line that symbolises a CH3 group (as you can see below)

For the eyes (Make 2):
With black ch3
Round 1: make 2sc in the 2nd loop from hook, then make 3sc in the first chain st you made. Make 2sc into the back loop of the first chain st you crocheted into.
Fasten off


Embroider highlights onto these and sew them onto the face, as you did for the previous bases. Embroider the mouth in place underneath, then sew the front and back sections together, stuffing firmly as you do so.




But why is Uracil present in RNA instead of Thymine?
When life first started, the genetic code was stored in  RNA instead of DNA. However, this was inherently unstable, because of the presence of the OH group of the 2' position on the ribose sugar (link to another pattern that explains this further). When organisms became more complex RNA was replaced with DNA, which consisted of deoxyribose, in which this OH group was missing. Another form of instability came from the fact that certain mutations in DNA can result in cytosine bases undergoing a chemical process that changed them into uracil bases. Luckily, our clever cells evolved a DNA repair enzyme called DNA glycosylase  (see enzyme pattern for more information on enzymes) to pick up on this and convert these mutated bases back into cytosine. This is why it is necessary that uracil is replaced with thymine, which has a very similar structure (so is still able to bind to adenine), but is not exactly the same. If uracil were present the DNA repair enzymes would go around converting all the uracil bases it found into cytosine, regardless of whether or not this is what they should actually be.

Part 2: The DNA helix

For the sugar-phosphate backbone (make 2):
With dark blue dk yarn ch9
Round 1: sc in the first chain st you made, then sc in every following chain st to make a loop
Round 2: sc in each of these 9 sts
Repeat round 2 until the backbone measures around 28cm

Fasten off 

Information on the DNA backbone 

This backbone of the DNA helix is made up of alternating molecules of phosphate and a sugar called deoxyribose. It is a strong structure that is not easily broken. The backbone strands have a polarity. This is different from the type of polarity you may have encountered in chemistry, but it gives us a way to specify the direction of the molecule. This polarity is determined by the direction of the deoxyribose molecules, and to see how this works we need to first examine the structure of these and how they fit together with the phosphate groups in the chain.

The deoxyribose sugar contains 5 carbon atoms, and they are numbered 1 - 5, with the first carbon atom being the one attached to the bases, and the 5th one being the side chain attached to the phosphate group. This means that the 3rd carbon atom will also be attached to a phosphate group. Therefore the DNA backbone is said to run from the 5' end (from the phosphate group attached to a carbon number 5) to the 3' end (i.e. the phosphate group attached to a carbon number 3). This gives the polarity of the strand. In DNA the two backbone strands run in opposite directions relative to each other, and this has important implications during processes such as DNA replication.

For the bases:

You need to make a total of 40 bases, and the number of G and C bases should be equal, as should the number of A and T bases.

With a 2mm hook make a magic loop with 5sc
Round 1 - 3: (3 rounds) sc in each st
Fasten of

To make up:

Sew the bases together in pairs (A with T, C with G)

Thread a length of wire through the backbone, and sew it to the edge so that it is held in place. This will keep the backbone rigid, so that the helix holds its shape better.

You will then need to sew the bases in place. Start by sewing one base pair to the bottom of the helix and another to the top, to ensure that the two backbone strands will match up. 

After this you need to sew the remaining base pairs in between. Try to twist the helix as you sew them on, to ensure that it will keep its helix shape. You should try to get between 1.5 and 2 full turns into the length of the helix (technically it should be 2 turns but I found that this was very difficult to achieve).

The final stage is to assemble the mobile. Cut 3 lengths of white yarn approx. 25cm long and tie them at equal intervals to the edge of the embroidery hoop. Tie the other ends to each other in the centre of the loop. Secure the ends in place with a dab of PVA glue.

Next you need to sew another section of yarn to the centre of the hoop, to where you tied the three lengths of yarn together. Sew the other end of this to the helix, so that the centre of the nucleus hangs about 25cm below the embroidery hoop. You should then attach the cuddly bases around the outside so that they hang at varying lengths, as shown below.

That's all for this pattern! I hope you have found it interesting. As I said I plan to make a whole series of biochemistry-related patterns - please let me know if there's anything particular you'd like me to make. This applies especially to if there was anything mentioned in this post that you were unsure about or thought wasn't explained properly - I'm planning to do some patterns going into more detail about some of the topics mentioned. 

Please let me know if you have any questions about this or any of my other patterns, either by leaving a comment below or via my Ravelry or Instagram pages.

You are very welcome to sell finished products but I do ask that you don't re-post this pattern or claim it as you're own. Thank you!

References:

thoughtco.com

factretriever.com

Carbon atom mobile

This pattern shows you how to make a model of a carbon atom, and it also explains a lot about the structure of the atoms, for those from a less scientific background.

Difficulty:

Medium
The crochet in this pattern is very easy but the construction is much more fiddly


You will need: 

• A 2.5mm crochet hook
• dk yarn in blue, red, and light pink
• white 4ply yarn
• An embroidery hoop
• craft wire (approx. 0.5mm in diameter)
• Some PVA glue
• A darning needle for sewing in loose ends
• A pair of scissors

The constituents of an atom
Atoms consist of 3 subatomic particles: protons, neutrons and electrons. We can think of these as little balls within out atom (although in reality its rather more complicated than this), with the protons and neutrons residing at the centre, and the electrons orbiting around the outside.


Protons
The protons are positively charged and have a mass approximately equal to that of the neutrons (1.67*10^-27kg). The number of protons determines the chemical properties of the atom, and dictates which element of the periodic table it is. The carbon atom that we will be creating contains (like all carbon atoms) 6 protons. The number of protons in the atoms of an element will correlates with its atomic number (the number in the top left-hand corner of each box on the periodic table below)

credit https://malouffschemblog.wordpress.com/2014/01/05/the-periodic-table-a-compilation-of-fun/

For the protons (make 6):

with red yarn make a magic loop with 6sc

Round 1: make 2sc in each st (12sc)

Rounds 2 - 4: (3 rounds) sc in each st

Round 5: sc2tog 6 times

stuff firmly

Round 6: sc2tog twice

Fasten off

Neutrons
A similar particle to the proton is the neutron. These uncharged particles are found in the nucleus of the atom, which is located at its centre. Unlike the protons and electrons, there can be varying numbers of neutrons in the nucleus of a given element. Atoms containing the same number of protons but different numbers of neutrons are known as isotopes of an element.
In this pattern we will be making the atomic isotope carbon-12, which contains 6 neutrons (it's known as carbon 12 because it contains a total of 12 nucleons). Other isotopes of carbon exist, however, including carbon-14, which contains 6 protons and 8 neutrons. The large number of neutrons makes it unstable, and thus it becomes radioactive.

For the neutrons (make 6):

with blue yarn make a magic loop with 6sc

Round 1: make 2sc in each st (12sc)

Rounds 2 - 4: (3 rounds) sc in each st

Round 5: sc2tog 6 times

stuff firmly

Round 6: sc2tog twice

Fasten off

How can most nuclei be stable?
If you know a little about physics, you may be aware that opposite charges attract and like charges repel. By this logic the nucleus should not be able to form, since all of the protons would reel each other instantly,so why is this not the case? Its all down to a force known as the Strong Nuclear force, which is an attractive force that acts between each of the nucleons (as the protons and neutrons are collectively called).  This exactly cancels out the repulsive force of the protons to allow the nucleus to exist in a stable state.

To make the nucleus sew each of these protons and neutrons together into a central ball.

Electrons

Around the nucleus is where the electrons are found. Electrons are negatively charged particles with a mass much much less than that of the protons and neutrons (the nucleons are about 1820 times more massive than the electrons). Because of their negative charge they will be attracted by the positively charged nucleus. If they were stationary they would fall straight into the nucleus, but this is prevented by their constant movement around the outer edges of the atom. 
The charge on each electron is equal and opposite to that of each proton. Because of this, and because an atom will always contain the same number of electrons as protons, the total charge of an atom will always be zero; it is electrically neutral. In cases where the number of electrons does not equal the number of protons, and thus an overall charge is achieved, our atom is known as an ion.
Unlike the protons and neutrons, which are each composed of 3 smaller particles called quarks, it is thought that electrons are fundamental (that is, they cannot be broken down into smaller parts).

For the electrons (make 6):

With pink yarn make a magic loop with 6sc

Rounds 1 - 2: (2 rounds) sc in each st

Stuff firmly

Round 3: sc2tog twice

Fasten off

To make up:

Cut a length of wire approx. 1m long, and thread 2 of the electrons onto it. Curl it round twice into a loop, then wind one end of the wire around the loop with the two electrons on. When each time you reach an electron thread the wire through said electron, then continue winding the wire around on the other side.

After you've done this you need to wind a length of white yarn around the wire to hide it. Seccure it every so often by threading the needle in between the two sections of wire.

Next you should cut another length of wire approx. 1.3m long, and thread the remaining 4 electrons onto it. Wind the wire into a double loop, and wind one end around the other as you did before, threading the other section of wire through each of the electrons as you encounter them.

You then need to wind a length of yarn around the wire, as you did for the other ring of electrons.

Why aren't the electrons all on the same loop?
The electrons around the outside of the nucleus will be arranged into set electron shells, each of which can only hold a certain number of electrons. The maximum possible number of electrons will increase for each subsequent shell (no. of electrons = 2n^2, where n is the shell number), meaning that the inner shell can only hold 2 electrons, whereas the 2nd shell can hold up to 8. (The reason for this relates to quantum physics, and I plan to make a pattern explaining it in greater detail in the future.)  The electrons will fill the inner shell first, as it has a lower energy level, and once this is full they will go on to start filling the 2nd shell.

Now we need to attach each of the part of the atom to our mobile.
Cut 3 lengths of white yarn approx. 25cm long and tie them at equal intervals to the edge of the embroidery hoop. Tie the other ends to each other in the centre of the loop. Secure the ends in place with a dab of PVA glue.

Next you need to sew another section of yarn to the centre of the hoop, to where you tied the three lengths of yarn together. Sew the other end of this to the nucleus, so that the centre of the nucleus hangs about 30cm below the embroidery hoop.

You then need to sew another length of yarn to the centre where all the yarn lengths meet. The other end of this should be looped around and tied in place, to allow the mobile to be hung up. The embroidery hoop should hang around 25-30cm below the top of this loop. Once again you should add a dab of PVA glue to all raw ends to prevent them from fraying.

You now need to sew the electron orbitals in place. Tie two lengths of yarn to the wire of the inner electron shell, one on each side. The other ends of the yarn should be sewn to the embroidery hoop. Try to ensure that the shell is positioned so that the nucleus lies in the centre. For best effect it should hang at an angle. You will most likely have to add at least one extra length of yarn to the shell to allow it to hang exactly the way you want it to. Play around with the exact positioning of the shell, and when you are happy with it secure the upper ends by adding a dab of PVA glue to where you have tied the yarn to the hoop.

A note on the relative positions of the electrons and nucleus

This atomic model is not to scale, as I'm sure you may have guessed, but what you may not know is just how out of scale it really is. There is a really good TEDx video explaining this, which states that if you scaled up an atom so that it was the size of a football stadium, then the nucleus in the centre would only be the size of a marble, and the electrons would be orbiting right at the edge of said stadium.

Next you will need to add the 2nd shell. As you did before, start by tying 2 lengths of yarn to the wire section of the shell, and then playing around with the positioning. You should try to get it so that the tilt of the 2nd shell is opposite that of the first shell you made. Once again you will most likely need to add a third length of yarn to hold it in the exact position you want. Play around with it for a bit, then secure the ends with a dab of PVA glue

Thats all! I hope you found this pattern interesting and informative. If you have any questions about this or any of my other patterns, please feel free to get in contact with me, either by leaving a comment below, emailing them to lhodginscrochet@gmail.com, or via my Ravelry or Instagram pages.

You are very welcome to sell finished products, but I do ask that you please don't re-post this pattern or claim it as your own. Thank you!