Genomic imprinting is an epigenetic (study of changes in organisms caused by modification of gene expression rather than alternation of the genetic code itself )phenomenon which in most cases is belived to occur in gametogenesis.
It occurs when both maternal and paternal alleles are present ,but one allele will be expressed while the other remains inactive.This process is necessary for development and may somehow regulate growth in the embryo .
Evidence - It came from experiments with androgenotes ( embryos with two paternal genomes ) and gynogenotes ( embryos with two maternal genomes ) , which were produced by nucler transplantation .These zygotes are formed , but neither type was able to undergoes further development.
Example -
1. Gene Igf2 is an imprinted gene being expressed only from the paternal chromosome .
2. H19 gene is an imprinted gene expressed only from the maternal chromosome .
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It is also called as uniparental disomy as only one allele is expressed either from father or from mother .
Genomic imprinting is rare in mammals because most of the genes are not imprinted. From a nuclear transplantation experiment in mouse during 1980 s it was confirmed that foe normal mammalian development both the maternal and paternal genomes are required.
In case of flowering plants some genes are found to be expressed from maternal genomes while some others are expressed exclusively from the alone paternal copy .( In case of Sweetbay -Magnolia virginiana )
In case of insects like honeybees and ants can reproduce either through fertilized eggs or unfertilized eggs. This sex determining system develops males from unfertilized eggs and females develop from fertilized eggs. The queen honey bee decides whether to fertilize an egg or to leave it unfertilized .
Improper imprinting in humans leads to some developmental abnormalities-
1.Prader-Willi-syndrome (when fathers copy is missing or there are 2 maternal parents.)
2.Angelman syndrome( when mothers copy is missing and there are 2 paternal parents .)
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It occurs when both maternal and paternal alleles are present ,but one allele will be expressed while the other remains inactive.This process is necessary for development and may somehow regulate growth in the embryo .
Evidence - It came from experiments with androgenotes ( embryos with two paternal genomes ) and gynogenotes ( embryos with two maternal genomes ) , which were produced by nucler transplantation .These zygotes are formed , but neither type was able to undergoes further development.
Example -
1. Gene Igf2 is an imprinted gene being expressed only from the paternal chromosome .
2. H19 gene is an imprinted gene expressed only from the maternal chromosome .
Genomic imprinting is rare in mammals because most of the genes are not imprinted. From a nuclear transplantation experiment in mouse during 1980 s it was confirmed that foe normal mammalian development both the maternal and paternal genomes are required.
In case of flowering plants some genes are found to be expressed from maternal genomes while some others are expressed exclusively from the alone paternal copy .( In case of Sweetbay -Magnolia virginiana )
In case of insects like honeybees and ants can reproduce either through fertilized eggs or unfertilized eggs. This sex determining system develops males from unfertilized eggs and females develop from fertilized eggs. The queen honey bee decides whether to fertilize an egg or to leave it unfertilized .
Improper imprinting in humans leads to some developmental abnormalities-
1.Prader-Willi-syndrome (when fathers copy is missing or there are 2 maternal parents.)
2.Angelman syndrome( when mothers copy is missing and there are 2 paternal parents .)
Thank you for visiting my blog.Please feel free to share your comment on this article ,Please subscribe and share the articles to get more such articles.
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