Quick Definition: What Is Horizontal Gene Transfer?

In plants and animals, most genes are passed from parent to child. Sometimes, however, genes can spread between unrelated individuals.


Most of us are used to the idea of vertical gene transfer: The passing down of genes vertically from parent to child. Hopefully that’s all pretty straight forward. Horizontal gene transfer, sometimes called lateral gene transfer or sideways gene transfer, is exactly what it sounds like: The passing of one or more genes through routes other than parent-to-offspring

Horizontal gene transfer is fairly common in bacteria. Some types of bacteria do this by actively attaching to and then sharing genes with other bacteria around them, even completely different species. Some bacteria can collect genes that have leaked out from other cells, use them as their own, and if all goes well, pass the foreign genes on to the next generation when they reproduce. Because of this, once a gene for antibiotic resistance evolves in one species, it can quickly spread to others which causes huge problems for us when trying to control diseases.

Scientists now know that horizontal gene transfer can happen in multi-celled plants, fungi, and animals as well. It appears to be rare but has interesting implications for the study of evolution.

Explore Further

Lessons from Wikipedia on Gene Transfer in bacteria:

Scientific papers on horizontal gene transfer allowing antibiotic resistance to spread between species

Scientific Papers on Horizontal Gene Transfers in animals, including people:


Our videos benefit from guidance and advice provided by experts in science and education. This animation is the result of collaboration between the following scientists, educators, and our team of creatives.

  • Joanna Masel, PhD
  • PZ Myers, PhD
  • Jon Perry
  • Anthony Danzl