If each individual has such a small amount of dna in their cells, how do the bands on the gel contain enough dna to be visible?

Hi,

Yes, every individual cell has a small amount of DNA but it is important to understand that before gel electrophoresis (a process in which DNA becomes visible on gel), the DNA is extracted in substantial amounts from a living organism like 5 micro litre, 10 microlitre etc. The extracted DNA is not from only one cell but many cells, infact depends upon the size of sample from which we took DNA, like 10 leaves, 20 leaves etc.

Now, coming towards the question that how do the bands on the gel contain enough DNA to be visible?

In order to visualize DNA we use a gel called agarose gel mixed with a dye called ethidium bromide and this dye's function is to bind with DNA.

Now, ethidium bromide is a molecule that can glow brightly under appropriate conditions. The dye inserts itself into the nitrogenous bases of the DNA and this is the ability we use to visualize DNA. When DNA sample is loaded in the gel and we apply electricity it moves the DNA towards the positive electrode and the DNA fragments separate on the basis of size. Now when  the DNA is separated, we observe the gel under UV light. When UV light falls on the gel, ethidium bromide glows and we can see beautiful bands of DNA. Thus this is the molecule responsible for tagging and visualizing the DNA.

Hope it helps!

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