Epigenetic inheritance

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Epigenetics is an emerging field in science. It is the idea that gene expression can be altered without changing the DNA sequence. This usually occurs by usually chemically altering the DNA or the associated transcription factors[1]. Most commonly in eukaryotes, the cytosine nucleotides are methylated using a DNA methylase enzyme after replication. These modifications occur preferentially upstream of the coding region, where is it rich in 5'-CG-3' dinucleotides that are known as CpG islands. The CpG islands give multiple sites for methylation, and 60-70% of the 5'-CG-3' dinucleotides in mammals are modified in this area. Methylation is associated with lower rates of transcription as the methyl group prevents transcription factors from effectively binding to the target DNA. An example of this is in Barr Bodies, where the DNA of the second 'X' chromosome is hypermethylated so transcription can't take place. There are other less common types of DNA modification, such as Histone modification and non-coding RNA associated gene silencing[2].

Epigenetic inheritance is useful because the epigenome can adapt to the environment much more than the genome can. It takes many generations for a genomic mutation to become useful to survival, whereas multiple epigenomic modifications can arise within a lifetime. The epigenome adapts to the environment, which allows an organism fo survive more easily, and these epigenomic modifications can be passed on through reproduction by genomic imprinting[3].

Genomic imprinting occurs in the germline. It is accompanied by heavy methylation on clusters of genes. Imprints are erased early in germline development so as to not stimulate any form of differentiation, so need to be re-established. This occurs in the form of remethylation later in the germline development.

Epigenetic inheritance is hard to detect, because unless there is a migration event or the organism's environment drastically changes, the diet and environment of the organism is going to be similar to it's offspring, therefore modification could arise independantly. Because of this, a modification can only be confirmed as being present through inheritance by the fourth generation of it's presence[4]

Some scientist suggested that epigenetic inheritance may highly related to Lamarckian inheritance based on a result from their experiment[5].

References

  1. Hartl, D. L. and Ruvolo, M. (2011) Genetics: Analysis of Genes and Genomes 8th edn. Jones and Bartlett Publishers
  2. Hartl, D. L. and Ruvolo, M. (2011) Genetics: Analysis of Genes and Genomes 8th edn. Unites States: Jones and Bartlett Publishers
  3. Hartl, D. L. and Ruvolo, M. (2011) Genetics: Analysis of Genes and Genomes 8th edn. Unites States: Jones and Bartlett Publishers
  4. University of Utah. 2015. Available at: http://learn.genetics.utah.edu/content/epigenetics/inheritance/ (Accessed: 2 December 2015)
  5. Hiroshi S. Inheritance of acquired traits in plants. Plant Signaling & Behavior 2010; 5(4)(n.d.): . https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2958583/ (accessed 1/12/2016).
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