Types of lethal alleles Lethal allele

1 types of lethal alleles

1.1 recessive lethals
1.2 dominant lethals
1.3 conditional lethals

types of lethal alleles
recessive lethals

a pair of identical alleles both present in organism results in death of organism referred recessive lethal alleles. though recessive lethals may encode dominant or recessive traits, fatal in homozygous condition. heterozygotes display form of disease phenotype, in case of achondroplasia. 1 mutant lethal allele tolerated, having 2 results in death. in case of homozygous achondroplasia, death invariably occurs before birth or in perinatal period. not heterozygotes recessive lethal alleles show mutant phenotype, case cystic fibrosis carriers. if 2 cystic fibrosis carriers have children, have 25 percent chance of producing offspring having 2 copies of lethal allele, resulting in death of child.

another example of recessive lethal allele occurs in manx cat. manx cats possess heterozygous mutation resulting in shortened or missing tail. crosses of 2 heterozygous manx cats result in 2 offspring displaying heterozygous shortened tail phenotype, , 1 offspring of normal tail length homozygous normal allele. homozygous offspring mutant allele cannot survive birth , therefore not seen in these crosses.

dominant lethals

alleles need present in 1 copy in organism fatal referred dominant lethal alleles. these alleles not commonly found in populations because result in death of organism before can transmit lethal allele on offspring. example in humans of dominant lethal allele huntington s disease, rare neurodegenerative disorder results in death. person exhibits huntington s disease when carry single copy of repeat-expanded huntingtin allele on chromosome 4.

conditional lethals

alleles fatal in response environmental factor referred conditional lethals. 1 example of conditional lethal favism, sex-linked inherited condition causes carrier develop hemolytic anemia when eat fava beans.