Maternal Effect on Shell Coiling in Snails
Maternal effects play a crucial role in determining the coiling direction of snail shells. The maternal inheritance of organelle genes controls certain traits in offspring, with the direction of shell coiling being a classic phenotype exhibiting maternal effects. The genotype of the female parent decides the phenotype of the progeny, showcasing a delayed effect of genotype. This phenomenon highlights how maternal factors influence specific traits in offspring development.
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Maternal Effect Shell Coiling in Snail by Suvasree Sahu
Maternal effects-shell coiling in snail The embryo is formed when a female gamete unites with the male gamete. However in majority of species female gamete is physically larger than the male gamete, and provides the cytoplasm for the developing embryo. Within the cytoplasm there are factors that are released by the nuclear genes of the females. These factors may have specific effects on the developing embryo. The female cytoplasm contributes mitochondria for all species and chloroplast in case of plants.
The DNA of these organelle control certain traits in offspring. Those phenotypic expressions that are controlled by organelle gene exhibit maternal inheritance. The classic phenotype which exhibits maternal effects is coiling direction in snail shell. The coiling phenotype that is seen in the offspring is controlled by genotype of the mother. In snails coiling of shell can be dextral (right hand coiling) or sinistral (left hand coiling). The direction of coiling is genetically controlled in snails. The dextral coiling is controlled by dominant allele D, while the sinistral coiling is controlled by a recessive allele d. So that in somatic cell dextral is DD and sinistral is dd.
The phenotype of progeny obtained in reciprocal cross depends on genotype of the female parent and not on the phenotype of the female parent. In the above crosses it is evident in the F1 generation the genotype Dd can be dextral as well as sinistral depending upon the genotype of the female parent. Similarly dd can be dextral is genotype of the female parent carries dominant allele (Dd). It should be carefully noted that the phenotype of the female parent does not have any effect on phenotype of progeny. It is genotype of female parent that decide the phenotype of offspring. This is an example of delayed effect of genotype.
