One way scientists may investigate the function of a gene is by making it inoperative within an organism (called gene ‘knockout’)

• The knockout can then be compared against a wild-type organism to deduce the function of the gene

Scientists can either knockout a gene across an entire organism or target the knockout to a particular tissue or organ

• There are various approaches that can be used to silence a gene – including the Cre-LoxP system, RNA interference or CRISPR-Cas9 editing

 A library of knockout organisms is available for some species for use as models in research

• Conditions that have been investigated using knockout organisms include obesity, diabetes, cancer, ageing and addiction
  

Mice are commonly used as model organisms due to a high degree of genetic similarity to humans – however other organisms have also been used

• The pigmentation gene was silenced in squid embryos to enhance research of squid physiology (squid have the largest brains of all invertebrates)