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.