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Alleles that cause an organism to die only when present in homozygous condition are called lethal alleles. The gene involved is considered an essential gene. “The Phenotypic manifestations of some mutant genes results in death of the individual earlier in prenatal or postnatal (postpartum) period prior to sexual matuarity. Such mutant genes are called Lethal genes.“ When Mendel's Laws were rediscovered, geneticists believed that mutations would only alter the appearance of a living organism. However, it was discovered that a mutant allele could cause death. When an essential gene is mutated, it can result in a lethal phenotype. If the mutation is caused by a dominant lethal genotype, the heterozygote for the allele will show the lethal phenotype, the homozygote dominant is impossible. If the mutation is caused by a recessive lethal genotype, the homozygote for the allele will have the lethal phenotype. Characteristics : i. They are not limited to X-Chromosome. ii. They are of more frequent occurrence in the autosome. iii. It involves the interaction of many genes. iv. It might interfere with the development of some vital organ such as heart or it might upset soe vital process chemical or physiological early in development. Types of Lethality : A. Dominant Lethal B. Recessive Lethal C. Conditional Lethal #DihybridCross #gene #HealthIndustry #Genetics #biology #DominantLethal #RecessiveLethal #ConditionalLethal #autosome #genes #phenotype #Heterozygote #genotype #Allele #mutations #lethalAllele #essentialGene
