Selection is multiplicative across loci, so that a genotype with i heterozygous recessive lethal
mutations has a relative fitness of [Mathematical Expression Omitted], where h is the dominance coefficient and the mean fitness in the population.
If inbreeding depression is the product of recessive lethal
and deleterious alleles that are maintained by mutation-selection balance, then inbreeding depression at equilibrium should decline with increased inbreeding (Lande and Schemske 1985; Charlesworth and Charlesworth 1987; Waller 1993).
According to the partial-dominance hypothesis, the cause of lower fitness of progeny derived from inbreeding as compared with outcrossing is the exposure of recessive or nearly recessive lethal
and deleterious mutations in the inbred offspring.
Theory suggests that in a large population the component of inbreeding depression maintained by nearly additive, mildly deleterious mutations, or genetic variance in quantitative characters, is difficult or almost impossible to purge by inbreeding, but that the recessive lethal
component of inbreeding depression is effectively purged by a low rate of self-fertilization (Lande and Schemske 1985; Charlesworth and Charlesworth 1987; B.
The genetic basis of x-rays induced recessive lethal
Meckel Gruber syndrome is a rare autosomal recessive lethal
disorder with wide spectrum of clinical manifestations.
To investigate how many recessive lethal
mutations are carried by humans on average, Ziyue Gao, a graduate student in the Genetics, Genomics and Systems Biology program, and her colleagues worked closely with a group of Hutterites, a religious community that settled in North America in the 1870s.
DMD is the most common X-linked recessive lethal
disease, with an incidence of approximately 1 in 3500 newborns (1).
"We don't yet understand why the number of recessive lethal
mutations might be relatively constant across distantly related organisms," said Gao.
(2011) identified five recessive lethal
haplotypes in three cattle breeds.
If a "recessive lethal
mutation" is defined as a mutation that results mainly in the premature death of homozygous individuals, sickle cell anemia is a recessive lethal
However, it is not yet known whether the genetic load revealed by inbreeding is composed primarily of genes that would respond readily to that selection (such as recessive lethal
alleles), primarily of genes that would not respond readily to selection (such as a genes showing overdominant fitness effects or genes with individually small effects), or different genetic bases in different populations.