Lethal Allele - 5th semester (CBCS)


What is lethal allele? What are the types of lethal allele with an example.

=> Lethal means something that can cause dead. If an individual have lethal allele than the  lethal allele can cause death of the individual. Contain gene that are highly essential for survive in case the the gene get mutated then it creates the lethal allele.

    In dominant lethal allele is in dominant form. In dominant allele the single allele can be able to cause death. It may be homozygous or heterozygous allele that caused lethality.

        In recessive lethal allele when  it is homozygous form that it can cause death of an organism. For example the recessive lethal allele is coat colour of mice. Here genotype AA is for agouti coat colour of mice & genotype AAY   for yellow coat colour when we cross between yellow coat colour mice then we get the following result

Now we have found that recessive lethal allele present in homozygous form in AYAY. So this mice will die. On the other hand yellow coat colour AAY that heterozygous condition & this mice will be survive because this gene is lethal but  for  lethality this gene is  recessive. So the phenotype will be yellow colour. On the other hand AA shows the agouti coat colour where no lethal allele was found .Hence it is shows the agouti coat colour. Thus this modified mendelian monohybrid add to ratio 3:1 to 2:1.

       Now in case of dominant lethality a single dominant lethal allele is responsible for death of an organism. It may be heterozygous as well as homozygous condition. This allele is commonly found in  populations because they die before transmitting  lethal allele to offspring. For ex.  Huntington disease.

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