Capsule 3 : What does Coronavirus do once in a cell?

22 April 2020 Julian Venables

Capsule 3

What does Coronavirus do once in a cell?

by Julian Venables and Philippe Fort

Having latched onto the cell, a virus fuses its membrane with that of the cell. The contents of the virus can thus disperse into the cell. So let’s focus on the really important part, for the future of the virus, namely the part carrying the instructions for how to make more viruses.

There is a lot of similarity between the way a virus infects a cell and how a sperm fertilizes an egg, so let me introduce sperm:egg fertilization a bit further. Every animal, including the human, starts its life as a single cell made from the fusion of a mother’s egg (oocyte) and a father’s sperm cell. The resulting hybrid cell contains a mix of the instructions from each parent. At fertilization, the sperm injects the father’s instructions into the egg but it adds none of the raw materials needed to copy itself. Luckily, as well as the mother’s instructions, the fertilised egg, known as the zygote, has all the raw materials needed to make a new-born! If you are confined at home with your Mum thanks to the coronavirus, she will gladly explain how that works! The virus does not want to make a half virus/half human (what would that even look like?) but rather wants to make just copies of itself, and lots of them. So what does the virus do?

In the springtime in the country you can hear the characteristic ‘cuc-koo’ song of the cuckoo bird. To make their fledglings, their lazy and nasty strategy is to lay their eggs in the nest of a different species of bird. After the egg hatches the fledgling cuckoo kicks the other baby birds out of the nest to hog all the food the parents bring for itself. That is exactly what a virus does. It goes into a cell to hijack all the cell’s resources to multiply itself, and that does damage. When lots of cells are infected by the virus it can even take the infected person’s life.

Computer viruses were so-named because they behave like real viruses. Like real biological viruses, they contain nothing but the instructions needed to recopy themselves and to spread to other computers. The important part of the coronavirus for these instructions is a molecule of the same type as that which carries the human’s genetic information. This consists of a long molecule called Deoxyribo Nucleic Acid, or DNA. Some viruses can even insert their DNA into the DNA of the cell they have infected. Luckily for us, coronavirus works a bit more simply than those viruses! In the next capsule we’ll talk in more detail about the ‘genetic’ instructions of the coronavirus that make it spread.

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