Gene Expression Challenge Questions 3

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Understanding Gene Expression Discussion Page

Challenge Question 3


Using the information presented in the seminar paper and your knowledge of gene expression, explain what is meant by epigenetic modification and why these modifications could potentially alter the phenotype that is expressed.


Newlands College- RKB 27th September, 2011

Epigenetic modification is a process by which the actual behaviour of genes is altered due to non-genetic factors. The non-genetic factors change the ability of a gene to be accessed within the chromatin and so it is not expressed as it would normally. In normal circumstances, specific genes are turned on and this results in production of proteins that bring about the coded for phenotype. The genes are unpacked from a condensed state within the chromosome so transcription factors can gain access. However, the process of epigenesis results in proteins made that are not specific to the genes. Evidence suggests that the packaging of the chromosomes is changed in the womb altering the ability of the gene to be properly unpackaged and transcribed. This results in a change in the phenotype.

It is understood that the environment that an offspring is exposed to in the womb has a huge impact on the gene expression of the offspring later. If a child does not get enough of specific nutrients such as protein or vitamins then the child is unable to develop. This causes genes to become altered to give the offspring a chance of adapting to the new environment. Protein helps in the development of the brain, but if a child lacks protein then the brain can not be developed further and so there are changes in the packaging of the chromosomes. When these are later unpackaged, it is found that the offspring may have learning difficulties.

Scientists know that environmental influences early in life cause epigenetic changes to the DNA and therefore there is a change in phenotype. There is no change in the sequence of bases in the DNA. Research shows that offspring’s born to mothers that were on a high fat or undernourished diet during pregnancy will potentially grow to have early puberty, higher chances of getting heart disease, type 2 diabetes and learning difficulties. Therefore, it is possible that epigenesis may have occurred resulting in the altering of the ability of specific genes to be expressed which in turn alters the phenotype. There is evidence that suggests mothers on balanced diet have offspring’s that start puberty at a later stage and have less chance of getting heart disease. If this is correct, then it means that a pregnant woman’s surrounding environment has a substantial impact on the prospects of the offspring in terms of having a strong immune system and chances of getting disease. The potential of a child may be partially decided before they are born. Therefore, to give every child a equal chance in succeeding and passing down fit genes then pregnant women must have an environment that is suited to the womb.