DNA
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LearningTranscript
00:00What are you talking about? I didn't wear your hat.
00:11That's not my hair.
00:14Okay, you got me.
00:22Dear Tim and Moby, do all animals have DNA?
00:26From Kevin.
00:27Yes, they do, Kevin.
00:29So do all plants, fungi, algae, and bacteria.
00:35Dinosaurs and other extinct life forms have DNA, too.
00:39It's the basis for all life on Earth.
00:42DNA stands for deoxyribonucleic acid.
00:46It's a complex molecule that kind of looks like a spiral staircase.
00:51This double helix shape forms into long strings.
00:54In humans and other multicellular life, DNA is unique to each individual, kind of like
00:59a fingerprint.
01:01One copy contains the complete instructions for building an organism.
01:05It's long.
01:07Stretched all the way out, a single set of human DNA is over six feet, and there's an
01:13identical copy inside the nucleus of nearly every cell in the body.
01:18Well, you can think of cells as miniature factories.
01:22But instead of cars or cell phones, these factories build proteins.
01:27That's the all-purpose construction material for life.
01:31Proteins can be molded to do just about anything.
01:33DNA tells your cells which proteins to build and how to build them.
01:38It tells cells in your eyes to form out of crystallins.
01:41These transparent proteins let light shine through so you can see.
01:45DNA tells your red blood cells to build a protein called hemoglobin.
01:50It captures oxygen as blood passes through the lungs.
01:54Crystallins, hemoglobin, and other proteins are precision machines.
01:59They're made of hundreds, sometimes thousands, of tiny parts.
02:03If just one of those parts gets messed up, the protein may not work.
02:08Human DNA holds instructions for building thousands of different proteins, used in more
02:13than 200 kinds of cell, forming dozens of different tissues, which all come together
02:20to make you.
02:22All of this information is stored within an incredibly simple code.
02:26It's built into DNA's structure in molecules we call bases.
02:30There are four different bases, and they stick together like puzzle pieces, always in the
02:34same pairs.
02:35They are cytosine, guanine, adenine, and thymine.
02:41You can think of bases as words in a special kind of language.
02:46They can be arranged into millions of different sequences, like sentences that spell out instructions
02:51for building any kind of protein.
02:53A section of DNA that codes for a single protein is called a gene.
02:58The average gene is thousands of base pairs long, and humans have more than 20,000 genes.
03:04But these protein coding sections represent only a tiny fraction of our complete DNA.
03:10The function of the rest, the non-coding DNA, is not entirely understood.
03:16To fit neatly inside a cell, the DNA spiral is wound into a coil, which is wound into
03:22an even bigger coil, which is wound into a structure called a chromosome.
03:27Up close, it looks like a big tangle, but it's actually precisely organized.
03:32This strong, flexible configuration keeps our personal info safe.
03:37Yeah, chromosomes come in pairs because of how we reproduce.
03:41In each of our 23 pairs, one's from the mother, and the other's from the father.
03:46Each of those is a shuffled-up version of the corresponding pair in your parents.
03:50So even though all your genes come from your parents, your chromosomes are unique.
03:55That's why family members tend to look similar, but have lots of differences, too.
03:59Eye color, hair type, and facial features are genetic traits.
04:04You inherit them in the genes you get from your parents.
04:08The number of chromosomes differs by species, kind of randomly.
04:13Humans have 46, lobsters have 100, corn has 20.
04:19Researchers have mapped the human genome, the complete sequence for human DNA.
04:24Comparing our genes to those of other life forms, we've discovered a lot in common.
04:29Humans share 96% of the same genes as chimpanzees, which isn't too surprising.
04:35But we also share 85% with mice, 60% with fruit flies, and 50% with bananas.
04:45We even have genes in common with bacteria and other single-celled life.
04:50This supports what Charles Darwin proposed in his theory of evolution more than 150 years ago.
04:56All life on Earth is connected, and likely traces back to a single ancestor.
05:03Yeah, some of the technology to come out of all this is pretty crazy.
05:07Like gene therapy, manipulating our DNA to cure diseases.
05:11That can mean turning a defective gene off, swapping a healthy gene in its place,
05:16or adding entirely new genes into our DNA.
05:20Scientists have been doing that for decades with crops.
05:24You can insert specific genes into plants to get better traits,
05:28like bigger apples or tomatoes that can grow in colder weather.
05:32The results are called genetically modified organisms, or GMOs.
05:36Some worry about the damage they might cause to the environment.
05:41Like if GMO crops crossbred with plants in nearby fields.
05:45That could have unpredictable results.
05:50Gene therapy may carry similar risks to our own health.
05:53But there's still so much we don't understand about DNA.
05:56So we need to be careful with these new technologies.
06:02Hey, let's see who this curly blonde hair belongs to.
06:13It's going to say Tim every time, isn't it?