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The Epigenetics of Identical Twins

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Identical twins are genetic carbon copies the DNA sequences of their genes are exactly the same. Yet physically, identical twins become increasingly different over time... ... why is this so? Genes provide the instructions for the development and maintenance of the body. Yet a second set of instructions known as the epigenome interacts with DNA to activate or suppress the expression of particular genes. Certain chemicals known as 'epigenetic tags' turn genes OFF or ON without changing the underlying genetic code. During fertilization one set of chromosomes from Dad and one set of chromosomes from Mum are combined to form an embryo. Epigenetic tags are erased from Mum and Dad's chromosomes during the first days after fertilization. However, on some genes the tags remain... ...these are known as IMPRINTED genes. Identical twins result when a single embryo splits in two. Each embryo has the same genome and the same epigenome. As the embryos develop cells differentiate into distinct types such as bone, muscle and skin. As each type specialises epigenetic tags activate and silence specific genes leading the cells to specialise further. Each cell type gradually takes on a unique epigenetic profile. Because the twins share the same environment their epigenomes are very similar at birth and through the early years of life. As the twins age, their environments begins to differ. Their genomes remain the same but signals from the environment act on the twins epigenomes to activate and silence different genes. Diet, for example is an environmental factor that can have an effect on the epigenome. Differences in physical activity can also cause epigenetic differences between the twins. Exposure to toxins can influence the epigenome. Stress also plays a role in shaping the epigenome. By the time the twins are well into adulhood their epigenomes, thus gene expression patterns, are very different... ... making each twin unique!

Video Details

Duration: 4 minutes and 41 seconds
Country: United Kingdom
Language: English
Producer: LearnGenetics
Director: LearnGenetics
Views: 1,067
Posted by: locumele on Oct 4, 2009

Why do the physical characteristics of identical twins diverge as they age? Follow the interaction of the environment and the genome in a pair of twins over time.

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