Maternal Inheritance Essay

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INTRODUCTION:-
Several experiments have shown the presence of the genes on chromosomes inside the nucleus. These genes inside nucleus control the phenotypes of the organisms and are transmitted from one generation to next generation. This hereditary transmission is known as Mendelian Inheritance. The nuclear genes are inherited from male and female parents in equal proportions and contribute equally to the genetic constitution of the offspring.
However, some inheritance patterns have been observed which do not follow the regular Mendelian inheritance or even the extensions of the Mendelian genetics. These variations confer that the genes for the inheritance of certain characters do not occur within the nucleus. These are present in cytoplasm
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Different phenotypes of progeny in reciprocal cross
In cytoplasmic inheritance, transmission of a trait usually occurs through only one parent i.e., uniparental inheritance. Uniparental transmission occurring through mother is called maternal inheritance and through father is called paternal inheritance. Maternal inheritance is most common uniparental inheritance.
Difference between maternal inheritance and maternal effect ???
Maternal inheritance occurs when the hereditary determinants of a trait are extra nuclear and genetic transmission is only through the maternal cytoplasm, whereas maternal effect occurs when the nuclear genotype of the mother determines the phenotypes of progeny. In maternal effect, the hereditary determinants are nuclear genes transmitted by both sexes.
EVIDENCE FOR EXTRA NUCLEAR INHERITANCE:
Evidence for cytoplasmic inheritance was first reported by Carl Correns (one of the rediscoverers of Mendel’s work) in Mirabilis jalapa (4o’clock plant) in 1908.
He observed that some branches in 4o’clock plant had white leaves, some had green and some had variegated leaves. The completely white leaves and the white areas in variegated leaves were devoid of chlorophyll that otherwise provides green colour. It comes out that the branch colour is determined by the phenotype of the ovule source. If the seeds (future progeny) were derived from ovules on branches with green leaves, all progeny plants have only green leaves. It doesn’t depend on the source of

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