There's an easy way to make the abstract idea of tiny DNA tangible and easier to grasp - with these experiments you can try out at home.
By
Leigh Nicholson

16 May 2016 - 4:24 PM  UPDATED 16 May 2016 - 4:25 PM

In life, things you can’t see are often the most difficult to understand and accept. Genetics is no different.

Our genetic information has been passed down and refined for billions of years, and it literally tells our cells what to make of us.

The human cell count in a body can get up to roughly 37.2 trillion cells, constantly doing work and then dying and being replaced with other cells to do that same work. Most of those cells have a nucleus – and in that nucleus you find your DNA.

But it gets even smaller than that.

DNA – the substance that carries all your genetic information in the format of strings upon strings of genes – is packed into structures called chromosomes. Humans have 46 chromosomes split up into 23 pairs; half from each parent. So even if you tend to look more like one of the people who gave you your genes, you still got half from each.

It’s a pretty incredible idea - that the emotional, behavioural, visual and all other differences between you and everyone else on Earth could be due to a slight variation in portions of your DNA.

A great way to understand such distant concepts is by making the invisible visible, so here are three experiments you can try at home to make genetics and DNA a little more tangible.

Strawberry DNA extraction

The crème de le crème of DNA experiments, and one that quickly proves – DNA is a physical form that you can actually pull out and look at.

This experiment literally pulls the DNA out of strawberries for you to see. Why strawberries? They have more DNA than most other fruits and are ‘octoploid’ - which means they have eight copies of each chromosome, unlike humans who got short-changed with only two (diploid).

For this experiment, you only need some isopropyl alcohol, salt, dish soap and a bunch of strawberries.

1.Chuck the isopropyl alcohol in the freezer

2. Put around 90ml of water into a small container (or beaker if you want to be fancy) and then add around 10ml of the dish soap

3. Add ¼ tsp of salt and then mix it up

4. Pour this liquid mess into a Ziploc bag with one or two strawberries

5. Squeeze out as much air as you can, seal it, and then smash it up

6. Just really pulverise that strawberry

7. Pour the solution through a sieve into a container, trying to get as much of the strawberry mess through as well

8. Now add around 5ml of your cold isopropyl alcohol

9. After a bit, you should have a white stringy substance forming that you can try and twirl around a pencil

10. That’s the DNA!

Why? The dish soap dissolved the cell membranes to get to that sweet genetic material. The salt broke down the nucleic acids into something a bit more manageable. And DNA isn’t soluble in alcohol, so it just sits there like the exposed genes it is. 

Cooking an egg with no heat
Image by Tim Ellis / CC BY-NC 2.0

This one is a bit more straightforward, and probably more off-putting. A crucial aspect of DNA molecules is their three-dimensional ‘double-helix’ structure. If you mess with the structure of proteins or DNA, or “denature” it, you ruin everything, which is effectively what you do when you cook an egg. Let’s proceed.

You’ll need an egg and, like most experiments, alcohol.

1. Crack that egg into a bowl

2. Put alcohol on the egg

3. Your egg should begin to resemble a weirder version of a fried egg

4, Don’t eat it, it’s gross. Trust me.

Although in this experiment you technically denatured the egg protein, not the DNA, it’s a good example of how important the 3D structure of DNA molecules is – it’s what holds everything together to allow for survival and replication; if you knock down a building, the businesses inside won’t do very well.

Messing with the structure of DNA can actually be really helpful in some research techniques; but apart from when your cells are dividing, you don’t want that happening inside your body.

Compare genetic sequences between animals

This one is a bit more research-oriented because there’s nothing a genetic scientist loves more than sitting in dark rooms pouring over thousands of arrangements of letters (so I presume).

There are hundreds of websites that are just databases for the genetic sequences of everything on Earth. A good one can be found here – but you don’t have to be a scientist to use it!

genomesize.com

1. Click on “Search Data” on the side of the page

2. Search different animals by putting in your own specifications or just by perusing through the different groups

3. The genome size of what you’re looking at will be the “c-value”

4. Look through different genomes and see if their size relates to the animal itself. For example, you can compare between a bee and an elephant and see how the results challenge your assumptions.

A thing to keep in mind is that the database defines c-value as the haploid DNA content. This means it is only counting one copy of the chromosome. So even if one animal has more copies of their DNA that won’t necessarily mean they have a larger genome.

Did you try any of these? What did you find? Tweet us at @SBS_Science!


 

Want more DNA, genes, and the stories they tell? Watch DNA Nation, starting Sunday 22 May, 8.30pm (AEST) on SBS. After they air, episodes will be available on SBS On Demand

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