Lethal allele

Lethal alleles were first discovered by Lucien Cuénot in 1905 while studying the inheritance of coat colour in mice.

It was not until 1910 that W. E. Castle and C. C. Little confirmed Cuénot's work, further demonstrating that one quarter of the offspring were dying during embryonic development.

[5] For live cases, inheriting both mutations lead to a grave prognosis where survival almost never extends beyond childhood.

[6] This is because the BRCA mutations also result in a severe subtype of Fanconi anemia (FA-S for BRCA1, FA-D1 for BRCA2), itself an extremely rare medical condition.

Crosses of two heterozygous Manx cats result in two-thirds of surviving offspring displaying the heterozygous shortened tail phenotype, and one-third of surviving offspring of normal tail length that is homozygous for a normal allele.

Achondroplasia is a skeletal system disorder caused by a recessive allele that can still result in a live birth in the homozygous state.

Not all heterozygotes for recessive lethal alleles will show a mutant phenotype, as is the case for cystic fibrosis carriers.

If two cystic fibrosis carriers have children, they have a 25 percent chance of producing offspring having two copies of the allele, eventually resulting in the death of the child without intensive treatment.

[8] An example in humans of a dominant lethal allele is Huntington's disease, a rare neurodegenerative disorder that ultimately results in premature death.

[14][15] For example, growing a ts DNA repair mutant at an intermediate temperature will allow some progeny phage to be produced.

In addition, it was found that an amber mutation produces a "nonsense codon" within a gene that causes polypeptide chain termination during translation.