[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:04.37,0:00:08.76,Default,,0000,0000,0000,,Identical twins are genetic carbon copies
Dialogue: 0,0:00:09.09,0:00:14.25,Default,,0000,0000,0000,,The DNA sequences of their genes are exactly the same
Dialogue: 0,0:00:14.25,0:00:19.45,Default,,0000,0000,0000,,Yet physically, identical twins become increasingly different over time...
Dialogue: 0,0:00:19.45,0:00:21.57,Default,,0000,0000,0000,,why is this so?
Dialogue: 0,0:00:27.33,0:00:29.03,Default,,0000,0000,0000,,Genes provide the instructions
Dialogue: 0,0:00:29.03,0:00:33.52,Default,,0000,0000,0000,,for the development and maintenance of the body.
Dialogue: 0,0:00:37.27,0:00:40.17,Default,,0000,0000,0000,,Yet a second set of instructions known as the epigenome
Dialogue: 0,0:00:40.17,0:00:42.54,Default,,0000,0000,0000,,interacts with DNA
Dialogue: 0,0:00:42.54,0:00:44.74,Default,,0000,0000,0000,,to activate or suppress
Dialogue: 0,0:00:44.74,0:00:48.35,Default,,0000,0000,0000,,the expression of particular genes.
Dialogue: 0,0:00:48.35,0:00:49.51,Default,,0000,0000,0000,,Certain chemicals
Dialogue: 0,0:00:49.51,0:00:52.52,Default,,0000,0000,0000,,known as {\i1}epigenetic tags{\i0}
Dialogue: 0,0:00:52.52,0:00:54.50,Default,,0000,0000,0000,,turn genes OFF
Dialogue: 0,0:00:58.86,0:01:00.23,Default,,0000,0000,0000,,or ON
Dialogue: 0,0:01:00.23,0:01:02.99,Default,,0000,0000,0000,,without changing the underlying genetic code.
Dialogue: 0,0:01:02.99,0:01:03.49,Default,,0000,0000,0000,,
Dialogue: 0,0:01:04.06,0:01:06.26,Default,,0000,0000,0000,,During fertilization
Dialogue: 0,0:01:06.26,0:01:09.04,Default,,0000,0000,0000,,one set of chromosomes from Dad
Dialogue: 0,0:01:09.04,0:01:11.50,Default,,0000,0000,0000,,and one set of chromosomes from Mum
Dialogue: 0,0:01:11.50,0:01:13.44,Default,,0000,0000,0000,,are combined to form an embryo.
Dialogue: 0,0:01:22.58,0:01:24.65,Default,,0000,0000,0000,,Epigenetic tags are erased
Dialogue: 0,0:01:24.65,0:01:26.75,Default,,0000,0000,0000,,from Mum and Dad's chromosomes
Dialogue: 0,0:01:26.75,0:01:31.06,Default,,0000,0000,0000,,during the first days after fertilization.
Dialogue: 0,0:01:31.06,0:01:34.39,Default,,0000,0000,0000,,However, on some genes the tags remain
Dialogue: 0,0:01:34.39,0:01:38.13,Default,,0000,0000,0000,,these are known as IMPRINTED genes.
Dialogue: 0,0:01:38.53,0:01:40.43,Default,,0000,0000,0000,,Identical twins result
Dialogue: 0,0:01:40.43,0:01:43.81,Default,,0000,0000,0000,,when a single embryo splits in two.
Dialogue: 0,0:01:48.46,0:01:50.84,Default,,0000,0000,0000,,Each embryo has the same genome
Dialogue: 0,0:01:50.84,0:01:53.56,Default,,0000,0000,0000,,and the same epigenome.
Dialogue: 0,0:01:58.82,0:02:00.72,Default,,0000,0000,0000,,As the embryos develop
Dialogue: 0,0:02:00.72,0:02:03.60,Default,,0000,0000,0000,,cells differentiate into distinct types
Dialogue: 0,0:02:03.60,0:02:07.09,Default,,0000,0000,0000,,such as bone, muscle and skin.
Dialogue: 0,0:02:07.09,0:02:10.06,Default,,0000,0000,0000,,As each type specialises epigenetic tags
Dialogue: 0,0:02:10.06,0:02:13.50,Default,,0000,0000,0000,,activate and silence specific genes
Dialogue: 0,0:02:13.50,0:02:17.14,Default,,0000,0000,0000,,leading the cells to specialise further.
Dialogue: 0,0:02:17.14,0:02:19.47,Default,,0000,0000,0000,,Each cell type gradually takes on
Dialogue: 0,0:02:19.47,0:02:23.49,Default,,0000,0000,0000,,a unique epigenetic profile.
Dialogue: 0,0:02:25.19,0:02:27.68,Default,,0000,0000,0000,,Because the twins share the same environment
Dialogue: 0,0:02:27.68,0:02:31.02,Default,,0000,0000,0000,,their epigenomes are very similar at birth
Dialogue: 0,0:02:31.02,0:02:34.52,Default,,0000,0000,0000,,and through the early years of life.
Dialogue: 0,0:02:34.52,0:02:35.92,Default,,0000,0000,0000,,As the twins age,
Dialogue: 0,0:02:35.92,0:02:39.19,Default,,0000,0000,0000,,their environments begins to differ.
Dialogue: 0,0:02:44.33,0:02:47.00,Default,,0000,0000,0000,,Their genomes remain the same
Dialogue: 0,0:02:47.00,0:02:49.34,Default,,0000,0000,0000,,but signals from the environment
Dialogue: 0,0:02:49.34,0:02:51.17,Default,,0000,0000,0000,,act on the twins epigenomes
Dialogue: 0,0:02:51.17,0:02:53.14,Default,,0000,0000,0000,,to activate and silence
Dialogue: 0,0:02:53.14,0:02:56.40,Default,,0000,0000,0000,,different genes.
Dialogue: 0,0:03:06.15,0:03:07.72,Default,,0000,0000,0000,,Diet, for example
Dialogue: 0,0:03:07.72,0:03:10.02,Default,,0000,0000,0000,,is an environmental factor
Dialogue: 0,0:03:10.02,0:03:12.64,Default,,0000,0000,0000,,that can have an effect
Dialogue: 0,0:03:12.67,0:03:14.48,Default,,0000,0000,0000,,on the epigenome.
Dialogue: 0,0:03:24.03,0:03:26.14,Default,,0000,0000,0000,,Differences in physical activity
Dialogue: 0,0:03:26.14,0:03:28.94,Default,,0000,0000,0000,,can also cause epigenetic differences
Dialogue: 0,0:03:28.94,0:03:30.97,Default,,0000,0000,0000,,between the twins.
Dialogue: 0,0:03:48.63,0:03:50.60,Default,,0000,0000,0000,,Exposure to toxins
Dialogue: 0,0:03:50.60,0:03:53.58,Default,,0000,0000,0000,,can influence the epigenome.
Dialogue: 0,0:04:04.81,0:04:07.22,Default,,0000,0000,0000,,Stress also plays a role
Dialogue: 0,0:04:07.22,0:04:09.75,Default,,0000,0000,0000,,in shaping the epigenome.
Dialogue: 0,0:04:20.96,0:04:22.53,Default,,0000,0000,0000,,By the time the twins
Dialogue: 0,0:04:22.53,0:04:24.53,Default,,0000,0000,0000,,are well into adulhood
Dialogue: 0,0:04:24.53,0:04:28.27,Default,,0000,0000,0000,,their epigenomes, thus gene expression patterns,
Dialogue: 0,0:04:28.27,0:04:30.10,Default,,0000,0000,0000,,are very different...
Dialogue: 0,0:04:30.10,0:04:32.48,Default,,0000,0000,0000,,... making each twin unique!