We are used to drawing DNA in its double-helix format, but it's not exactly in this form inside the cells. The DNA double strand is about 2 nm wide, and this is very, very small. But the length of the stretched DNA strand is way too large to fit inside the nucleus of the cell.
The solution is to pack all these strands. With the help of proteins, the DNA is entangled inside the nucleus but in an organized way which allows gene expression. But can we see DNA?
For this, let's try something new: to extract and visualize DNA from fruits. We will only need some material and you can easily repeat the experiment. We'll extract DNA from strawberries.
Strawberries are soft fruits, easy to macerate and are octaploid. This means they have 8 copies of the chromosomes in each cell. We humans are diploids, we only have 2 copies of each chromosome in the nucleus of our cells, one that we receive from our father and another from our mother.
First, we need to prepare a lysis solution. Cells are delimited by membranes, that we need to break to get to DNA. Since plants have cell wall and membranes of phospholipids, which are like fats, we can use detergent to break them.
That's right, that dishwasher detergent. A mixture of detergent in water with a dash of salt will cause the membranes to rupture. To ease the breakage of the cellular wall and the action of the detergent, we need to macerate the pieces of the fruit very well.
The DNA will be diluted in water with all the rest of the fruit. To separate the DNA from all this mixture of cell debri, we'll filter it. Filtration allows the cell debris to be retained and the DNA dissolved in the water to pass through the gauze.
If we think about the DNA molecule, it has a part of phosphate which has a negative charge, giving the molecule a polarity, and since the molecule of water is also polar, DNA gets very well diluted in water, and also invisible. The sodium chloride which was added in the lysis solution will help to separate the DNA, causing it to be neutralized and to stop being so soluble in water. To finish the DNA separation we use alcohol.
Alcohol will dehydrate the DNA, making fewer water molecules to be available to stay together with the DNA. Adding alcohol slowly we can see the DNA precipitating. It looks like a little cloud or wet cotton.
Because we have many, many strands together we can see the entangled DNA. If you liked this super easy experience and want to see more video like this, give a thumbs-up and comment below. See you next time!
