Temperature-sensitive mutant

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Temperature-sensitive mutants are variants of genes that allow normal function of the organism at low temperatures, but altered function at higher temperatures.


Most temperature-sensitive mutations affect proteins, and cause loss of protein function at the non-permissive temperature. The permissive temperature is one at which the protein typically can fold properly, or remain properly folded. At higher temperatures, the protein is unstable and ceases to function properly. These mutations are usually recessive in diploid organisms.

Permissive temperature[edit]

The permissive temperature is the temperature at which a temperature-sensitive mutant gene product takes on a normal, functional phenotype.[1] When a temperature-sensitive mutant is grown in a permissive condition, the mutated gene product behaves normally (meaning that the phenotype is not observed), even if there is a mutant allele present. This results in the survival of the cell or organism, as if it were a wild type strain. In contrast, the nonpermissive temperature or restrictive temperature is the temperature at which the mutant phenotype is observed.

Use in research[edit]

Temperature-sensitive mutants are useful in biological research. They allow the study of essential processes required for the survival of the cell or organism. Mutations to essential genes are generally lethal and hence temperature-sensitive mutants enable researchers to induce the phenotype at the restrictive temperatures and study the effects. The temperature-sensitive phenotype could be expressed during a specific developmental stage to study the effects.


In the late 1970s, the budding yeast secretory pathway, essential for viability of the cell and for growth of new buds, was dissected using temperature-sensitive mutants, resulting in the identification of twenty-three essential genes.[2]

In the 1970s, several temperature-sensitive mutant genes were identified in the fruit fly, such as shibirets, which led to the first genetic dissection of synaptic function.[3] In the 1990s, the heat shock promoter hsp70 was used in temperature-modulated gene expression in the fruit fly.[4]


  1. ^ "Permissive temperature". Biology-Online Dictionary.
  2. ^ Novick, P.; Field, C.; Schekman, R. (August 1980). "Identification of 23 complementation groups required for post-translational events in the yeast secretory pathway". Cell. 21 (1): 205–215. doi:10.1016/0092-8674(80)90128-2. ISSN 0092-8674. PMID 6996832.
  3. ^ Yoshihara M, Ito K (2012). "Acute Genetic Manipulation of Neuronal Activity for the Functional Dissection of Neural Circuits — A Dream Come True for the Pioneers of Behavioral Genetics". Journal of Neurogenetics (Review). Informa Healthcare USA. 26 (1): 43–52. doi:10.3109/01677063.2012.663429. PMC 3357893 – via Taylor & Francis Online.
  4. ^ Brand M, Jarman AP, Jan LY, Jan YN (1993). "asense is a Drosophila neural precursor gene and is capable of initiating sense organ formation" (PDF). Development. 119: 1–17.