Thalamus and hypothalamus

The thalamus and hypothalamus together form a part of the brain known as the diencephalon, which resides at the centre of the brain. This pattern in one in a series of pattern that fit together to form a life-sized human brain, and also includes details on how to make the optic nerve. I have already published the pattern for the cerebellum/brainstem and the ventricles/corpus collosum.

Note that the thalamus/ hypothamus are shown in green in the image above, with the optic nerve in gold. The blue section is the ventricles.

Difficulty:

Easy - difficult

The main difficulty comes from the fiddlyness of the hypothalamus

You will need:

• A 2.5mm crochet hook
• A 1mm crochet hook
• A 0.8mm crochet hook (optional)
• Anchor creativa fino 4ply cotton in green
• Rico essentials #10 cotton in emerald and gold
• Polyester toy stuffing
• A darning needle for sewing up

For each of the thalami (make 2):
With green 4ply yarn and a 2.5mm crochet hook make a magic loop with 5sc

Round 1: make 2sc in each st (10sts)
Round 2: sc5, make 2sc in the next st, sc2, make 2sc in the following st, sc (12sts)
Round 3: sc6, make 2sc in the next st, sc3, make 2sc in the following st, sc (14sts)
Round 4: sc7, make 2sc in the next st, sc3, make 2sc in the following st, sc2 (16sts)
Round 5: sc9, make 2sc in the next st, sc4, make 2sc in the following st, sc (18sts)
Rounds 6 - 10: (5 rounds) sc in each st
Round 11: sc, sc3tog, sc, sc3tog, sc2, sc3tog, sc, sc3tog, sc (10sts)
Stuff firmly
Round 12: sc2tog 5 times (5sts)
Fasten off

For the centre bit:
With the green 4ply and 2.5mm hook ch6
Round 1: sc in the first chain st you made, then sc in each of the following 5 chain sts to make a loop (6sts)
Fasten off

Sew this between the two lobes to connect them. It should be positioned slightly closer to the magic loop end compared to where you fastened off.

(ignore the optic nerve for the minute-we'll come to that later)

Note that if you intend to make a complete brain, make the ventricles first. After this you should sew the connecting section to one side of the thalamus, before threading it through the hole in the centre of the ventricles and sewing the other end to the other thalamus (see images below)

For the hypothalamus:

With a 1mm crochet hook and emerald #10 yarn ch4
Round 1: sc in the 2nd chain st from hook and the next chain st. Make 3sc in the first chain st you made, then sc in the back of the previous chain st you crocheted into. Make 2sc in the back of the first chain st you crocheted into (8sc)
Round 2: Make 2sc in the first st, sc2, make 3hdc in the next st, sc2, make 2sc in each of the last 2sts (13sts)
Round 3: Slip1, make 3hdc in the next st, sc3, ch1, make 2hdc in the following st, ch1 sc3, make 2hdc in the next st, slip2, make 3hdc in the last st (21sts(including the chain sts))
Round 4: Sc in each st
Round 5: (Note that this is slightly more than 1 round. The number of stitches is the number you should have after the round is complete) Sc7, sc2tog, sc, sc2tog, sc7, sc3tog (17sc)
Round 6: Sc8, ch6, skip the remaining sts of this round
Round 7: Sc6, sc3tog between the next 2sts and following chain st, sc in the next 5 chain sts (12sc)
Round 8: Sc5, sc3tog, sc4 (10sc)
Round 9: make 4hdc in the first st, sc3, sc3tog, sc3 (11sts)
Round 10: Sc2, make 2sc in each of the next 2sts, sc3, sc3tog, sc (11sts)
Round 11: Sc, sc5tog, sc, sc2tog twice (5sts)
Fasten off

Round 5: Ch6, then sc in the 2nd st after the last st you crocheted into on round 4. Sc in the next 7sts

Round 6: Sc in the first 5 chain sts of the last round, then sc3tog between the last chain st and the following 2sts. Sc in the next 6sts (12sc)
Round 7: Sc4, sc3tog, sc5 (10sc)
Round 8: Sc3, sc3tog, sc3, make 4hdc in the last st (11sts)
Round 9: Sc2, sc3tog, sc3, make 2sc in each of the next 2sts, sc (11sts)
Round 10: Sc, sc2tog twice, sc, sc5tog (5sts)
Fasten off

Rejoin yarn to row 4 to one of the sts you haven't crocheted into yet. 

Row 5: Sc in this st. ch1, turn
Rows 6 - 9: (4 rows) Sc in this st. ch1, turn

Row 10: sc in this st
Fasten off

Sew the end you just fastened off to the other st you haven't crocheted into in row 4, then stuff lightly and sew the sides of this bit you just made to the chain sts you made of row 5, as shown below

Sew to the  front of the thalamus (the end closest to where you sewed the connecting part). The cast-on chain should be on the side furthest away from the thalamus, as shown below.

Front-on view

The optic nerve is an optional extra., which you can choose to add if you wish. I am also planning to included this design in a future pattern I publish detailing how to make all of the cranial nerves, so if you're planning to make the whole brain you don't need to worry about making this yet.

For the optic nerve:

With gold #10 yarn and 0.8mm hook make a magic loop with 6sc

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

Round 3: sc2tog, sc4 (5sc)

Round 4: sc2tog, sc3 (4sc)

Rounds 5 - 8: (4 rounds) sc in each st

Rounds 9 - 10: (2 rounds) slip2, hdc2

Rounds 11 - 15: (5 rounds) sc in each st

---

Fasten off neatly

Repeat as before up to --- 

Round 16: sc3, sc in the 'new' st of the first section you made, sc in the next 2sts (6sc)

Round 17: sc in the first 3sts of the last round, ch1

Round 18: slip the first 2sts of last round, then hdc in the next st and chain st (4sts)

Rounds 19 - 21: (3 rounds) sc in each st

Fasten off

Rejoin yarn to round 16 to the st after the last st you crocheted in before you made the ch1 on round 17

Round 17: Sc in this st and the next 2sts, ch1

Round 18: slip2, hdc2

Rounds 19 - 21: (3 rounds) sc in each st

Fasten off

Sew the ends of this nerve to the outer edges of the thalami as shown below. (The hypothalamus isn't shown in these images but the principal is the same)

That's all for this pattern, I hope you have enjoyed it! If you have any questions about this or any of my other patterns please don't hesitate to get in touch - you can leave a comment below or contact  me via my  Ravelry or  Instagram (Instagram is best if you're hoping for a speedy reply). You can also email me at lhodginscrochet@gmail.com if you prefer :)

As always you are very welcome to sell finished products but please don't re-post this pattern or claim it as your own. Thank you!

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