[Script Info]
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[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.38,0:00:11.11,Default,,0000,0000,0000,,You have about 20,000 genes in your DNA.
Dialogue: 0,0:00:11.11,0:00:13.95,Default,,0000,0000,0000,,They encode the molecules that\Nmake up your body,
Dialogue: 0,0:00:13.96,0:00:17.99,Default,,0000,0000,0000,,from the keratin in your toenails,\Nto the collagen at the tip of your nose,
Dialogue: 0,0:00:17.99,0:00:21.29,Default,,0000,0000,0000,,to the dopamine surging around\Ninside your brain.
Dialogue: 0,0:00:21.29,0:00:23.68,Default,,0000,0000,0000,,Other species have genes of their own.
Dialogue: 0,0:00:23.68,0:00:26.09,Default,,0000,0000,0000,,A spider has genes for spider silk.
Dialogue: 0,0:00:26.09,0:00:30.81,Default,,0000,0000,0000,,An oak tree has genes for chlorophyll,\Nwhich turns sunlight into wood.
Dialogue: 0,0:00:30.81,0:00:33.33,Default,,0000,0000,0000,,So where did all those genes come from?\N
Dialogue: 0,0:00:33.33,0:00:35.22,Default,,0000,0000,0000,,It depends on the gene.
Dialogue: 0,0:00:35.22,0:00:40.25,Default,,0000,0000,0000,,Scientists suspect that life\Nstarted on Earth about 4 billion years ago.
Dialogue: 0,0:00:40.25,0:00:42.74,Default,,0000,0000,0000,,The early life forms were\Nprimitive microbes
Dialogue: 0,0:00:42.74,0:00:47.38,Default,,0000,0000,0000,,with a basic set of genes for\Nthe basic tasks required to stay alive.
Dialogue: 0,0:00:47.38,0:00:50.18,Default,,0000,0000,0000,,They passed down those basic genes\Nto their offspring
Dialogue: 0,0:00:50.18,0:00:52.32,Default,,0000,0000,0000,,through billions of generations.
Dialogue: 0,0:00:52.32,0:00:57.96,Default,,0000,0000,0000,,Some of them still do the same jobs\Nin our cells today, like copying DNA.
Dialogue: 0,0:00:57.96,0:01:01.94,Default,,0000,0000,0000,,But none of those microbes had genes\Nfor spider silk or dopamine.
Dialogue: 0,0:01:01.94,0:01:06.69,Default,,0000,0000,0000,,There are a lot more genes on Earth today\Nthan there were back then.
Dialogue: 0,0:01:06.69,0:01:11.47,Default,,0000,0000,0000,,It turns out that a lot of those\Nextra genes were born from mistakes.
Dialogue: 0,0:01:11.47,0:01:15.60,Default,,0000,0000,0000,,Each time a cell divides,\Nit makes new copies of its DNA.
Dialogue: 0,0:01:15.60,0:01:20.17,Default,,0000,0000,0000,,Sometimes it accidentally copies\Nthe same stretch of DNA twice.
Dialogue: 0,0:01:20.17,0:01:24.59,Default,,0000,0000,0000,,In the process, it may make an extra copy\Nof one of its genes.
Dialogue: 0,0:01:24.59,0:01:27.82,Default,,0000,0000,0000,,At first, the extra gene works the same\Nas the original one.
Dialogue: 0,0:01:27.82,0:01:32.05,Default,,0000,0000,0000,,But over the generations, \Nit may pick up new mutations.
Dialogue: 0,0:01:32.05,0:01:35.39,Default,,0000,0000,0000,,Those mutations may change how\Nthe new gene works,
Dialogue: 0,0:01:35.39,0:01:38.14,Default,,0000,0000,0000,,and that new gene may duplicate again.
Dialogue: 0,0:01:38.14,0:01:41.95,Default,,0000,0000,0000,,A surprising number of our \Nmutated genes emerged more recently;
Dialogue: 0,0:01:41.95,0:01:45.04,Default,,0000,0000,0000,,many in just the past few million years.
Dialogue: 0,0:01:45.04,0:01:50.06,Default,,0000,0000,0000,,The youngest evolved after our own species\Nbroke off from our cousins, the apes.
Dialogue: 0,0:01:50.06,0:01:54.15,Default,,0000,0000,0000,,While it may take over a million years\Nfor a single gene to give rise
Dialogue: 0,0:01:54.15,0:01:55.90,Default,,0000,0000,0000,,to a whole family of genes,
Dialogue: 0,0:01:55.90,0:01:58.87,Default,,0000,0000,0000,,scientists are finding that once \Nthe new genes evolve,
Dialogue: 0,0:01:58.87,0:02:01.70,Default,,0000,0000,0000,,they can quickly take on\Nessential functions.
Dialogue: 0,0:02:01.70,0:02:06.40,Default,,0000,0000,0000,,For example, we have hundreds of genes\Nfor the proteins in our noses
Dialogue: 0,0:02:06.40,0:02:08.65,Default,,0000,0000,0000,,that grab odor molecules.
Dialogue: 0,0:02:08.65,0:02:11.30,Default,,0000,0000,0000,,The mutations let them grab\Ndifferent molecules,
Dialogue: 0,0:02:11.30,0:02:14.95,Default,,0000,0000,0000,,giving us the power to perceive trillions\Nof different smells.
Dialogue: 0,0:02:14.95,0:02:19.38,Default,,0000,0000,0000,,Sometimes mutations have\Na bigger effect on new copies of genes.
Dialogue: 0,0:02:19.38,0:02:22.91,Default,,0000,0000,0000,,They may cause a gene to make its\Nprotein in a different organ,
Dialogue: 0,0:02:22.91,0:02:25.45,Default,,0000,0000,0000,,or at a different time of life,
Dialogue: 0,0:02:25.45,0:02:29.18,Default,,0000,0000,0000,,or the protein may start doing\Na different job altogether.
Dialogue: 0,0:02:29.18,0:02:33.64,Default,,0000,0000,0000,,In snakes, for example, there's a gene\Nthat makes a protein for killing bacteria.
Dialogue: 0,0:02:33.64,0:02:38.24,Default,,0000,0000,0000,,Long ago, the gene duplicated\Nand the new copy mutated.
Dialogue: 0,0:02:38.24,0:02:40.96,Default,,0000,0000,0000,,That mutation changed\Nthe signal in the gene
Dialogue: 0,0:02:40.96,0:02:43.20,Default,,0000,0000,0000,,about where it should make its protein.
Dialogue: 0,0:02:43.20,0:02:45.80,Default,,0000,0000,0000,,Instead of becoming active in\Nthe snake's pacreas,
Dialogue: 0,0:02:45.80,0:02:50.57,Default,,0000,0000,0000,,it started making this bacteria-killing\Nprotein in the snake's mouth.
Dialogue: 0,0:02:50.57,0:02:55.05,Default,,0000,0000,0000,,So when the snake bit its prey,\Nthis enzyme got into the animal's wound.
Dialogue: 0,0:02:55.05,0:02:57.95,Default,,0000,0000,0000,,And when this protein proved\Nto have a harmful effect,
Dialogue: 0,0:02:57.95,0:03:00.06,Default,,0000,0000,0000,,and helped the snake catch more prey,
Dialogue: 0,0:03:00.06,0:03:01.92,Default,,0000,0000,0000,,it became favored.
Dialogue: 0,0:03:01.92,0:03:05.73,Default,,0000,0000,0000,,So now what was a gene in the pancreas\Nmakes a venom in the mouth
Dialogue: 0,0:03:05.73,0:03:07.78,Default,,0000,0000,0000,,that kills the snake's prey.
Dialogue: 0,0:03:07.78,0:03:10.99,Default,,0000,0000,0000,,And there are even more incredible ways\Nto make a new gene.
Dialogue: 0,0:03:10.99,0:03:13.88,Default,,0000,0000,0000,,The DNA of animals and plants\Nand other species
Dialogue: 0,0:03:13.88,0:03:18.20,Default,,0000,0000,0000,,contain huge stretches without any\Nprotein coding genes.
Dialogue: 0,0:03:18.20,0:03:22.05,Default,,0000,0000,0000,,As far as scientists can tell,\Nits mostly random sequences
Dialogue: 0,0:03:22.05,0:03:24.68,Default,,0000,0000,0000,,of genetic giberish that serve\Nno function.
Dialogue: 0,0:03:24.68,0:03:28.70,Default,,0000,0000,0000,,These stretches of DNA\Nsometimes mutate, just like genes do.
Dialogue: 0,0:03:28.70,0:03:31.82,Default,,0000,0000,0000,,Sometimes those mutations\Nturn the DNA into a place
Dialogue: 0,0:03:31.82,0:03:34.31,Default,,0000,0000,0000,,where a cell can start reading it.
Dialogue: 0,0:03:34.31,0:03:36.98,Default,,0000,0000,0000,,Suddenly the cell is making a new protein.
Dialogue: 0,0:03:36.98,0:03:40.52,Default,,0000,0000,0000,,At first, the protein may be useless,\Nor even harmful,
Dialogue: 0,0:03:40.52,0:03:43.91,Default,,0000,0000,0000,,but more mutations can \Nchange the shape of the protein.
Dialogue: 0,0:03:43.91,0:03:45.100,Default,,0000,0000,0000,,The protein may start\Ndoing something useful,
Dialogue: 0,0:03:45.100,0:03:48.62,Default,,0000,0000,0000,,something that makes an organism\Nhealthier, stronger,
Dialogue: 0,0:03:48.62,0:03:50.94,Default,,0000,0000,0000,,better able to reproduce.
Dialogue: 0,0:03:50.94,0:03:55.23,Default,,0000,0000,0000,,Scientists have found these new genes\Nat work in many parts of animal bodies.
Dialogue: 0,0:03:55.23,0:03:58.64,Default,,0000,0000,0000,,So our 20,000 genes have many origins,
Dialogue: 0,0:03:58.64,0:04:03.58,Default,,0000,0000,0000,,from the origin of life, to new genes\Nstill coming into existence from scratch.
Dialogue: 0,0:04:03.58,0:04:07.20,Default,,0000,0000,0000,,As long as life is here on Earth,\Nit will be making new genes.