[CAITLIN:] So, ah, what's going on here? [FELICIA:] I'm doing crafts. I'm crafty. [CAITLIN:] I don't even know if I want to ask. [FELICIA:] Well, Cait, I was inspired by art. You always tell me to get out more often and experience culture. Well, here it is. [CAITLIN:] Okay, so we're looking at a chromosome. [FELICIA:] Exactly! A chromosome. It holds all the genetic information of life, but what is a chromosome? Why is it important? How does it fit into our story? For that matter, how does it fit into our cells? [CAITLIN:] So, you're trying to build a giant cell and show how DNA is packaged. [FELICIA:] Exactly. And what about genes? How do they fit in? What does it all mean? [CAITLIN:] Well, find out on [Both:] DNA Decoded. [Music] [FELICIA:] Okay. But before we start, I've got a question. We know that the nucleobase combines with phosphate and sugar to create a nucleotide. And we know how nucleotides come together to make up a strand of DNA that looks like a twisted ladder with two sides that go in opposite directions: five prime to three prime and three prime to five prime. [CAITLIN:] Okay. That's all correct, but what's your question? [FELICIA:] How does it all fit into a cell? I mean, humans have about a 100 trillion cells and the nucleus of most of those cells contains 23 chromosomes that code for about 20,000 genes. So, we're looking at billions of base pairs, about three billion base pairs in each cell. [CAITLIN:] Well, how do you think it all fits? [FELICIA:] So, here's what I'm working on. See this yarn? This yarn is a DNA double helix. The different colours represent different genes. And this is the nucleus of the cell. The nucleus contains all of our chromosomes, all the instructions we need to build proteins. [CAITLIN:] Okay. [FELICIA:] So, what's the trick? How do we get billions of base pairs into a nucleus? [CAITLIN:] Would you like me to show you? [FELICIA:] Yes. [CAITLIN:] Okay. This ball is a special protein called a histone. [FELICIA:] Okay. I'm with you. [CAITLIN:] A histone is like a spool that winds DNA tightly into a structure called a nucleosome. Here, help me wrap this DNA around the histone. [Felicia wraps yarn around the tennis ball.] [FELICIA:] And these histones are going to help us fit all this genetic material into the nucleus? [CAITLIN:] Hold on for a second. You need to pump your brakes. First, we need to make 23 chromosomes. [FELICIA:] That's a lot of yarn, I mean DNA. Maybe we'll do that another time? [CAITLIN:] I guess so. We'll leave the chromosome building to the professionals. Want to see how histones do it? [FELICIA:] Wow, that is magic! And now our chromosomes fit inside our nucleus. [FELICIA:] And our nucleus fits inside our cells. There are other cellular compartments in this cell. [FELICIA:] If we think of the entire cell as a factory, each department has a different function. The furnace of this cellular factory is the mighty mitochondria. You can think of it as the powerhouse of the cell. [CAITLIN:] I'm calling for a pause on all science-related puns. [FELICIA:] And I am saying "no way" and ignoring that. Moving on! The endoplasmic reticulum, the production centre, is where proteins are made. Proteins are like the robots in a factory, each with a specific job to do. The processing centre in this factory is the Golgi body. It helps package and label proteins and sends them on their way. So, there you go! Our crafty way of showing you how the crafty cell packs so much information into its tiny self. [CAITLIN:] Do you want to play a game of tennis? [FELICIA:] You know, sometimes you are so impossible. [Music] [FELICIA:] Woo-hoo! Movie time!! What's the feature today? [CAITLIN:] Cells, cells and more cells. All of these images were captured using a microscope and some of the images have been artificially coloured to make the cells or compartments pop out. Brain cells. They're responsible for motor coordination. Adipocytes or fat cells. And, my personal favourite, red blood cells. They look like doughnuts. [CAITLIN:] Remember when I told you about the nucleus? Well, red blood cells are one of a handful of cells that do not have a nucleus. [FELICIA:] What? [CAITLIN:] I know, I know. I just told you how important the nucleus is but red blood cells have one job: to carry oxygen. [FELICIA:] Wow! Great movie. What's up next? [CAITLIN:] Well, that's all I've got for now. But if you're interested in learning more about the different organelles, then head on over to the supplementary material. You can find even more images there. [FELICIA:] Cool. I'm kind of hungry. Let's go get some doughnuts. [CAITLIN:] How are you hungry? I heard you snacking on popcorn during the movie. [FELICIA:] And your point is? [CAITLIN:] All right. I know a spot.