Haploinsufficiency occurs when a diploid organism only has a single working copy of a wild-type gene (with the other copy inactivated by hereditary mutation or another mechanism), and the single functional copy of the gene does not produce enough of a gene product (typically a protein) to bring about a wild-type condition, leading to an abnormal or disease state.

Haploinsufficiency is therefore an example of genetic dominance, as only one mutant gene is necessary to produce a phenotype effect.

Human diseases brought exhibiting haploinsufficiency include:

• Achondroplastic dwarfism
• Huntington's Disease
• polydactyly

References

• Griffiths, Anthony J. et al (2005). Introduction to Genetic Analysis (8th Ed.). W.H. Freeman. ISBN 0-7167-4939-4

Genetics