Under what circumstances might a lethal dominant allele persist in a population?

Under what circumstances might a lethal dominant allele persist in a population? there are only two correct answers late onset (lethality occurs after reproductive age) nonrandom mating high desease frequency in the population natural selection against the allele incomplete penetrance

Answer

Answer: incomplete penetrance, late onset (lethality occurs after reproductive age) Reason: Incomplete penetrance, pleiotropy, locus heterogeneity are the crucial complication which predominantly due either a novel induced mutation or due to late onset of age and genetic imprinting. Due to variable expression the resultant phenotype is abnormal as meticulous genetic abnormalities but even differs in the intensity of the symptoms in the family from one phenotype to another phenotype. In hereditary hemochromatosis disease we can find the affect of variable genetic allelic expression result in the different phenotypes in the same family. The recurrence of the disease is due to the random mutations in the family and due to the reproduction of low affected people with normal unaffected individuals. The severity of a disease in a family completely dependent on autosomal dominancy considerably associated with incomplete penetrance, thereby the resultant phenotype either he or she do not express disease symptoms even though there is an expression of abnormal genotypic expression. Thereby we can consider dominant inheritance is the cause for disease severity but not recessive inheritance. In case of Pleiotrophy one affects 2 or more apparently not linked phenotypic traits there by more gene could be affected (cystic fibrosis). 1. Mendel’s law of independent assortment states that, during meiosis, each member of a pair of genes on homologous chromosomes tends to be randomly distributed into gametes independently of how other chromosomes are distributed. It results in giving all possible combinations in equal frequency. However, we generally do not observe the Mendelian inheritance all the time, the non-Mendelian inheritance occur in the following cases. 1. Polygenic traits 2. Incomplete dominance 3. Co dominance 4. Sex related genetic effects 5. Pleiotropy 6. Incomplete penetrance

7. Environmental influences.

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