Magnetic 3D-Printed Chromosome Models - Mitosis and Meiosis

Hey fellow makers! I love biology and making models with 3d printing, so I'm thrilled to share my very first Instructable with this amazing community. This project is close to my heart, and I'm proud to finally contribute. If you're remixing this, please attribute it back to me. I can't wait to see the improvements and remixes you come up with.

These are models of chromosomes, centromeres and spindle fibres that I made in order to help me better understand mitosis and meiosis, especially chromosomal crossover.

They consist of 2 parts: Firstly, the chromosome, with 2 centromeres and 2 chiasma pieces; Secondly, the centromere and the spindle fibres.

I wanted the model to have these properties:

1. The centromeres of sister chromatids should be magnetic so that they should be able to stick together in metaphase but also be pulled apart to demonstrate anaphase.
2. The centromeres should have a hole so that a hook, representing the spindle fibres/microtubules, can slip into the hole and can be used to pull apart the sister chromatids during anaphase.
3. The chromosomes should have chiasma which may be swapped between homologous chromosomes to show chromosomal crossover.

Please click on the images as I have added notes to clarify difficult steps.

I have linked the Onshape documents of the models below.

Onshape centromere model

Onshape chiasma model

You will need:

1. A 3D printer - I used an Ender 3 S1, which is a FDM printer, but you can use a resin printer.
2. A filament spool or resin for the 3D printer. I used PLA, but any rigid filament or resin should work
3. Circular magnets - 1.5mm thick with a 5.9mm diameter. (The magnets should be axially magnetized, which means that the opposite faces have opposite poles. )
4. Wire pipe cleaners / chenille stems, those used for arts and crafts, of different colors.
5. A hot glue gun.
6. Large popsicle sticks.

Slice and print the attatched STLs. I used Cura 5.4.0. Use these settings:

1. Layer height: 0.28 mm
2. Walls: 2 walls
3. Infill: 10%, Lightning or Cubic

No support or build plate adhesion is needed.

Print 2 centromeres and 2 chiasmas per "set" (a pair of sister chromatids).

1. Attach the magnets to the plastic pieces with hot glue. Ensure the magnet poles are facing the correct direction, as shown in the images.
2. Glue one magnet with the north pole facing outwards and one magnet with the south pole facing outwards in each centromere piece.
3. Glue one magnet with the north pole facing outwards and one magnet with the south pole facing outwards per pair of chiasma.

1. Take 2 centromere pieces, 2 chiasma pieces, and 2 whole pipe cleaners.
2. Cut the two whole pipe cleaners into 3 half-pieces and 2 quarter-pieces.
3. Thread two of the half-pieces into the holes of one centromere piece. Thread the last half-piece and one quarter-piece into the holes of the other centromere piece.
4. Then thread the ends of both quarter pieces through one chiasma each.

If you are making more than one "set", ensure that the magnet polarity of both pairs of chiasma are facing the same way - refer to the images.

Linked below is the assembly video.

1. Cut a large popsicle stick into parts 4 cm long.
2. Drill two holes at the ends of each part.
3. Thread and tie a pipe cleaner through each of the two holes and bend the ends into hooks.

The assembly video is linked below.

Have fun with your new chromosome models! Go out and share them with your fellow teachers, students or friends.

Credits for images: Khan Academy, Ameoba Sisters