Balanced Lethal Systems: An Evolutionary Mystery

Frontiers for Young Minds, vol. 9

Abstract

When a female crested newt lays her clutch of about three-hundred eggs, half of these will never hatch. What an incredible waste! It turns out that these newts suffer from a deadly hereditary disease called a balanced lethal system. Here is how it works: in a balanced lethal system, there are two distinct versions of a particular chromosome. Newts need both to live. However, which version a fertilized newt egg gets from its father and mother is random. Therefore, there is a 50% chance that it receives the same version twice—and misses the other half of the critical pair. Hence, half of the eggs end up with the wrong chromosome combination and die. The newts are not the only example; balanced lethal systems are found in some plants and insects as well. Why something so disadvantageous as a balanced lethal system would ever evolve is still a big, evolutionary mystery!

Authors 4

1. Willem R. M. Meilink Aachen Naturalis Biodiversity Center Evolution & Biodiversity Institute of Biology Leiden

   Leiden University · Naturalis Biodiversity Center

   Affiliation as printed

   Naturalis Biodiversity Center , Leiden , Netherlands

   Evolution & Biodiversity, Institute of Biology Leiden, Leiden University, Leiden, Netherlands

   Naturalis Biodiversity Center, Leiden, Netherlands

2. James France Aachen Evolution & Biodiversity Institute of Biology Leiden Naturalis Biodiversity Center

   Leiden University · Naturalis Biodiversity Center

   Affiliation as printed

   Evolution & Biodiversity , Institute of Biology Leiden , Leiden University , Leiden , Netherlands

   Evolution & Biodiversity, Institute of Biology Leiden, Leiden University, Leiden, Netherlands

   Naturalis Biodiversity Center, Leiden, Netherlands

3. Manon Chantal de Visser Aachen Evolution & Biodiversity Institute of Biology Leiden Naturalis Biodiversity Center

   Leiden University · Naturalis Biodiversity Center

   Affiliation as printed

   Evolution & Biodiversity , Institute of Biology Leiden , Leiden University , Leiden , Netherlands

   Evolution & Biodiversity, Institute of Biology Leiden, Leiden University, Leiden, Netherlands

   Naturalis Biodiversity Center, Leiden, Netherlands

4. Ben Wielstra Aachen Evolution & Biodiversity Institute of Biology Leiden Naturalis Biodiversity Center

   Leiden University · Naturalis Biodiversity Center

   Affiliation as printed

   Evolution & Biodiversity , Institute of Biology Leiden , Leiden University , Leiden , Netherlands

   Evolution & Biodiversity, Institute of Biology Leiden, Leiden University, Leiden, Netherlands

   Naturalis Biodiversity Center, Leiden, Netherlands