Related Experiment Video
Updated: Jul 9, 2026

Navigating MARRVEL, a Web-Based Tool that Integrates Human Genomics and Model Organism Genetics Information
Published on: August 15, 2019
What causes partial F1 hybrid viability? Incomplete penetrance versus genetic variation
Hernán López-Fernández1, Daniel I Bolnick
1Section of Ecology, Evolutionary Biology and Systematics, Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America.
Background:
Interspecific hybrid crosses often produce offspring with reduced but non-zero survivorship. In this paper we ask why such partial inviability occurs. This partial inviability could arise from incomplete penetrance of lethal Dobzhansky-Muller incompatibilities (DMIs) shared by all members of a hybrid cross. Alternatively, siblings may differ with respect to the presence or number of DMIs, leading to genotype-dependent variation in viability and hence non-Mendelian segregation of parental alleles in surviving F1 hybrids.
Methodology/Principal Findings:
We used amplified fragment length polymorphisms (AFLPs) to test for segregation distortion in one hybrid cross between green and longear sunfish (Lepomis cyanellus and L. megalotis). Hybrids showed partial viability, and twice as much segregation distortion (36.8%) of AFLPs as an intraspecific control cross (18.8%). Incomplete penetrance of DMIs, which should cause genotype-independent mortality, is insufficient to explain the observed segregation distortion.
Conclusions/Significance:
We conclude that F1 hybrid sunfish are polymorphic for DMIs, either due to sex-linked DMI loci (causing Haldane's Rule), or polymorphic autosomal DMI loci. Because few AFLP markers were sex-linked (2%), the most parsimonious conclusion is that parents may have been heterozygous for loci causing hybrid inviability.
More Related Videos
Related Concept Videos
Incomplete Dominance
Genetic Variation
Genes exist in different versions called alleles, which...
Mutation, Gene Flow, and Genetic Drift
Trihybrid Crosses
Some of Mendel’s crosses examined three pairs of contrasting characteristics. Such a cross is called a trihybrid cross. A trihybrid cross is a combination of three individual monohybrid crosses. For example, plant height (tall vs. short), seed shape (round vs. wrinkled), and seed color (yellow vs. green).
The F1 generation plants of a trihybrid cross are heterozygous for all three traits and produce eight gametes. Upon self-fertilization, these gametes have an equal chance to...
Understanding Species and Reproductive Barriers
Principles of Pharmacogenetics: Types of Genetic Variants

