Archive for the ‘Genetics’ Category

The Central Dogma been challenged

Monday, October 31st, 2011

We spoke of epigenetics in the context that the Central Dogma of gene transcription and translation is not a simple linear relation but is part of a complex cellular network system. The old theory of genetic determinism based sole on the sequence of gene determining the coding of genetic messages to form amino acids and proteins that drive biological behaviour is now been challenged.

Even within the gene sequences, scientists are finding that the exons interspersed with many non-coding introns and their splicing prior to translation is variable . After transcription of a gene to messenger RNA, the way transcriptions of introns are removed, and the exons are spliced together by enzymes before translation and assembly of amino acids into proteins is complex and not linear. {{{0}}}

The cloning of Dolly turns the central dogma on its head. The ability of cytoplasmic factors in the oocyte whose nuclear DNA material is replaced with that of mature adult DNA material challenges the dogmatic linear relation of nuclear DNA transcription to mRNA that is translated to protein synthesis. Cytoplasmic factors are able to modify the mature DNA, in this case adult mammary cells and reprogram them into progenitor stem cells from which Dolly was cloned.

Epigenetic mechanisms such as methylation and histones acetylation provide a good explanation of how environmental factors affect gene expression. We are not doomed by the gene sequence we inherited. We could modify such expressions with proper diet and lifestyle. There are evidence such positive modifications on gene expression could occur within months rather than years that mutations would take in certain situations where the organism has to adapt to adverse environment. Example of mutations such as the 11p15.5 mutation in haemoglobin in sickle cell anemia is a longer term adaption to malaria infested environment. Epigenetic mechanisms are shorter term adjustments for quick adaptations. Such epigenetic mechanisms are in operation on the time and are just being studied more intensely in recent times.

The breakthrough of genetic sequencing and splicing has allowed genetic engineering to flourish in the biotech industry producing a number of breakthrough biological pharmaceutical products and GMO agricultural produce. However, the lack of understanding of how these transgenic material behave in the ecosystem might create serious environmental issues. Some of these issues are already surfacing in the GMO agricultural produce.

The pundits are arguing if we should regulate the use of genetic engineering until a better understanding of how the newly created genes and their products interact with the ecosystem before long term global catastrophes occur.

Epigenetics – an emerging area of gene research

Friday, August 12th, 2011

In biology, and specifically genetics, epigenetics is the study of changes in gene expression caused by mechanisms other than changes in the underlying  DNA sequence – hence the name epi- (Greek: ???– over, above, outer) -genetics. Examples of such changes might be DNA methylation or histone deacetylation, both of which serve to suppress gene expression without altering the sequence of the silenced genes. {{{0}}}

These changes may remain through cell divisions for the remainder of the cell’s life and may also last for multiple generations. However, there is no change in the underlying DNA sequence of the organism; instead, non-genetic factors cause the organism’s genes to behave (or “express themselves”) differently.

One example of epigenetic changes in eukaryotic biology is the process of cellular differentiation. During morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo which in turn become fully differentiated cells. In other words, a single fertilized egg cell – the zygote – changes into the many cell types including neurons, muscle cells, epithelium, blood vessels etc. as it continues to divide. It does so by activating some genes while inhibiting others through the epigenetic process.

Currently, what have been well research and documentation are 2 known mediating processes – methylation and histone deacytylation. These processes could be activated by a number of environmental stimuli, in utero and childhood development, aging, diet and drugs.