Science 10 with CSS teacher

Mutations occur naturally, but they are also caused by UV radiation (for example sunlight) or chemicals (for example cigarettes, pesticides and some food preservatives).

Mutations can also be genetic (inherited from parents and passed on to children). For example, Down syndrome (also called Trisomy-21) is caused by an extra copy of the 21st chromosome.

Whatever their cause, mutations don't always have the same effects. A mutation can be

• positive: the mutation is beneficial to an organism, helping it to survive and reproduce. Positive mutations can also turn on genes beneficial to the organism or turn off genes that are harmful to the organism.  For example - you can mutate a piece of bacterial DNA that was "turned off" to turn it on- this can make it less susceptible or more susceptible to antibiotics. It would be beneficial to the bacteria, but detrimental to us if we are trying to get rid of it.

• negative: the mutation reduces the organism's chance of surviving and reproducing. Many pesticides and herbicides target the species by blocking a protein from being made by altering (mutating) the DNA. Some antibiotics work by blocking DNA synthesis or protein synthesis in the bacteria, causing bacteria to die. If the bacteria mutates to no longer need the specific protein, then the antibiotic becomes useless.

• neutral: the mutation doesn't affect the organism's ability to survive

Click here to learn more about the pros and cons of mutations.