Question: Why, when DNA replicates, there are faults in it?

Emma Meaburn answered on 1 Feb 2019:

The process of DNA replication (the process by which DNA makes a direct copy of itself) has a lot of repair mechanisms in place to try ensure that errors do not creep in – and if they do, they are fixed. This is generally quite effective, but if the errors are not fixed they are passed on to the new cell (which no longer recognises them as errors) they become mutations. The consequences of the new mutation will vary depending on where in the genome it has happened (in a gene or not in a gene), but generally most have very minor effects and have little consequence for the health and function of the cell – or might even be beneficial!