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What is Genetic Resistance?


Genetic resistance occurs when an individual organism’s genes afford it greater tolerance to certain environmental conditions. Oftentimes when we talk about genetic resistance we are specifically referring to about tolerance for a particular chemical or other substance in the environment.


For example, throughout most of history, humans only drank milk as infants and couldn’t fully digest it as adults. However, a beneficial mutation that allows humans to digest milk as adults spread through some of the human population, and now many people can enjoy milk throughout their entire lives.


These people are genetically tolerant of the lactose found in milk due to having a particular mutation. People who are not genetically tolerant (also known as lactose intolerant) are unable to break down lactose and experience digestive upset and other unpleasant symptoms as a result of consuming milk.


Genetic resistance can have much more sinister implications. In some parts of Africa, malaria and other mosquito-borne diseases pose a large human health risk, so pesticides are often used to protect human homes and cities from disease-carrying mosquitoes. However, if these pesticides are used too often and too widely the mosquitoes in that area may become genetically resistant to the pesticides due to natural selection.



















(Skeeze, 2015)


The same phenomenon can occur with antibiotics. When populations of bacteria are repeatedly exposed to antibiotics, only the bacteria with mutations that make them genetically resistant will survive to reproduce. This leaves behind a population of antibiotic-resistant bacteria. For example, MRSA, or methicillin-resistant Staphylococcus aureus is a type of staph bacteria that is difficult to treat because it is genetically resistant to many common antibiotics. 


Image Citation


Skeeze (photographer). (2015). Bacteria electron microscope [photography]. Retrieved from

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