Types of Lethal Genes

Lethal Genes:

Certain genes are known to control the manifestation of some phenotypic traits as well as affect the viability of the organism. Some other genes have no effect on the appearance of the organism but affect the viability alone. These genes are known as lethal or semilethals. The lethal genes are always recessive for their lethality and express the lethal effect only in homozygous conditions.

Types of Lethal Genes:

Lethals may be three types:

    1. Dominant Lethal

    2. Recessive Lethal

    3. Conditional Lethal

Dominant Lethal:

The dominant lethal genes are lethal in homozygous conditions and produce some defective or abnormal phenotype in heterozygous condition. Their most serious effect in heterozygous condition may also cause death.

Recessive Lethal:

The recessive lethals produce lethal effect only in homozygous condition. Their heterozygous are normal. Therefore, recessive lethals remain unnoticed in the population but are established in the population. These are detected only when two heterozygous persons get married.

Conditional Lethal:

The genes which may be normal to the individual in a particular environment may prove to be lethal when environmenr is changed.