WEBVTT - FunStuff Playlist 04: Do Humans and Bananas Really Share Half Their DNA? 0:00:01.920 --> 0:00:06.480 Welcome to brain Stuff production of I Heart Radio. Hey 0:00:06.519 --> 0:00:10.639 brain Stuff, Lauren vog Obam. Here, during party conversation or 0:00:10.680 --> 0:00:12.719 at a trivia night, you may have heard the fun 0:00:12.760 --> 0:00:15.640 little fact that humans and bananas share fifty or even 0:00:15.720 --> 0:00:19.319 six of the same DNA. There seems to be a 0:00:19.320 --> 0:00:21.400 lot of differences, though, between a person and a piece 0:00:21.400 --> 0:00:23.439 of yellow fruit, starting with the fact that one is 0:00:23.480 --> 0:00:26.000 an animal and the other as a plant. But actually 0:00:26.040 --> 0:00:29.160 there is some truth to that startling statistic, but it's 0:00:29.160 --> 0:00:32.520 not the whole truth. This urban legend of sorts likely 0:00:32.560 --> 0:00:35.320 originated from a program run by the National Human Genome 0:00:35.360 --> 0:00:39.519 Research Institute back in although similar data may have been 0:00:39.560 --> 0:00:44.320 run elsewhere. Genetics expert Dr Lawrence Brody and his colleagues 0:00:44.360 --> 0:00:47.800 generated some banana human information to be included as part 0:00:47.880 --> 0:00:51.360 of an educational Smithsonian Museum of Natural History video called 0:00:51.560 --> 0:00:55.720 The Animated Genome. That video noted that DNA between a 0:00:55.840 --> 0:01:00.560 human and a banana is forty one percent similar. In 0:01:00.640 --> 0:01:03.240 order to find out how this similarity was determined, we 0:01:03.320 --> 0:01:07.240 talked with Dr Brodie himself. He explained that first, it's 0:01:07.240 --> 0:01:11.000 important to understand the difference between DNA and protein products. 0:01:11.640 --> 0:01:14.119 You can think of DNA as the blueprint of a house, 0:01:14.480 --> 0:01:17.720 and protein products as the actual house because all of 0:01:17.760 --> 0:01:21.759 the information is in there. Then think of human DNA 0:01:21.840 --> 0:01:24.480 as the blueprint for a ranch home, and banana DNA 0:01:24.640 --> 0:01:27.480 is that of a condo. In each house, a bunch 0:01:27.480 --> 0:01:30.679 of things are similar the plumbing, bathrooms, kitchen, but the 0:01:30.800 --> 0:01:33.800 end products are both quite different. And that's how it 0:01:33.840 --> 0:01:36.800 works with humans versus just about everything else from bananas 0:01:36.800 --> 0:01:40.360 two chimpanzees. The second thing to keep in mind is 0:01:40.400 --> 0:01:43.160 that genes, which are the regions of DNA that code 0:01:43.160 --> 0:01:45.880 for these proteins, only make up about two per cent 0:01:46.040 --> 0:01:49.960 of your DNA. In order to compare humans and bananas, 0:01:50.160 --> 0:01:52.480 scientists first looked at the sequences of genes in a 0:01:52.520 --> 0:01:56.600 typical banana gino. Brodie said. We then used these DNA 0:01:56.680 --> 0:01:59.640 sequences to predict the amino acid sequence of all the 0:01:59.640 --> 0:02:02.480 protein means that would be made from those genes. We 0:02:02.600 --> 0:02:06.640 then did the same process for all human genes. All 0:02:06.680 --> 0:02:09.760 of the protein sequences were placed in a file. Next, 0:02:09.880 --> 0:02:13.000 the scientists compared the protein sequence from each banana gene 0:02:13.240 --> 0:02:18.079 to every human gene. Brodie said. The program compares how 0:02:18.120 --> 0:02:20.679 similar the sequence of the banana genes are to each 0:02:20.760 --> 0:02:24.360 human gene. Program kept any matches that were more similar 0:02:24.360 --> 0:02:27.679 than one would expect by chance. The program continued doing 0:02:27.680 --> 0:02:31.280 this gene by gene. All told, more than four million 0:02:31.320 --> 0:02:34.959 comparisons were done, resulting in about seven thousand best hits 0:02:35.040 --> 0:02:38.880 between the two genomes. Then the percent similarity score for 0:02:38.919 --> 0:02:42.359 each of those hits was averaged. Bertie said, this gave 0:02:42.440 --> 0:02:46.160 us the result of about this is the average similarity 0:02:46.200 --> 0:02:51.360 between proteins gene products, not genes. Gene products or proteins 0:02:51.360 --> 0:02:54.720 are the biochemical material resulting from a gene becoming functional. 0:02:55.840 --> 0:02:59.320 Brodie continued, Of course, there are many many genes in 0:02:59.320 --> 0:03:02.359 our genome do not have a recognizable counterpart in the 0:03:02.400 --> 0:03:06.840 banana genome, and vice versa. In case that's a bit 0:03:06.840 --> 0:03:10.919 difficult to chew and swallow, let's break it down. Essentially, 0:03:11.040 --> 0:03:13.560 they took all of the banana genes and compared them 0:03:13.639 --> 0:03:16.440 one at a time to human genes. From that they 0:03:16.480 --> 0:03:19.440 called a degree of similarity. If the banana had the 0:03:19.480 --> 0:03:22.560 gene but the human didn't, that didn't get counted. And 0:03:22.680 --> 0:03:26.080 about sixty of our genes have a recognizable counterpart in 0:03:26.080 --> 0:03:31.480 the banana genome, Brodie explained. Of those, the proteins encoded 0:03:31.480 --> 0:03:34.960 by them are roughly identical. When we compare the amino 0:03:35.000 --> 0:03:37.920 acid sequence of the human protein to its equivalent in 0:03:38.080 --> 0:03:41.880 the banana. It may seem shocking that so many genes 0:03:41.880 --> 0:03:44.000 and so many of the proteins that they create are 0:03:44.080 --> 0:03:47.280 similar in two such vastly different beings as a person 0:03:47.320 --> 0:03:50.080 in a banana, But when you think about it, it's 0:03:50.200 --> 0:03:53.840 not that shocking, Brodie explained. If you think about what 0:03:53.880 --> 0:03:56.640 we do for living and what a banana does, there's 0:03:56.680 --> 0:03:58.480 a lot of things we do the same way, like 0:03:58.560 --> 0:04:01.840 consuming oxygen. A lot of those genes are just fundamental 0:04:01.920 --> 0:04:06.560 to life. So when people repeat the percentages being a 0:04:06.600 --> 0:04:10.000 similarity of DNA, actually what the research looked at was 0:04:10.040 --> 0:04:14.080 the similarity of gene products, Brodie reassured us it's a 0:04:14.120 --> 0:04:17.080 pretty minor mistake. The kernel that you would take home 0:04:17.200 --> 0:04:19.120 is that we have something in common with a banana 0:04:19.200 --> 0:04:22.440 and a potato and the pine tree. That part is true. 0:04:23.040 --> 0:04:25.279 The fine point about the gene products or the DNA, 0:04:25.680 --> 0:04:28.080 it's easy to see how that would get translated incorrectly. 0:04:29.520 --> 0:04:31.839 So a scientist looked at the DNA sequence of a 0:04:31.839 --> 0:04:34.000 banana and compared it with the DNA of a human 0:04:34.320 --> 0:04:38.640 it would not align. We also spoke via email with 0:04:38.720 --> 0:04:42.400 Mike Francis, a PhD student in bioinformatics at the University 0:04:42.400 --> 0:04:46.279 of Georgia. He explained, you share fifty of your DNA 0:04:46.360 --> 0:04:49.040 with each of your parents, but with bananas, we share 0:04:49.080 --> 0:04:53.880 about of our genes. As we said earlier, genes make 0:04:53.960 --> 0:04:57.320 up just two of your DNA, So what's the other 0:04:58.200 --> 0:05:01.200 made up of? Well, eight percent of the rest of 0:05:01.240 --> 0:05:04.320 your DNA regulates genes as to whether a gene should 0:05:04.360 --> 0:05:07.919 be turned on or off. The other appears to have 0:05:08.080 --> 0:05:11.560 unknown functions or functions that have been lost through evolution. 0:05:12.360 --> 0:05:15.919 Francis said, these unknown sections of DNA used to commonly 0:05:15.960 --> 0:05:18.479 be called junk DNA because it was thought to do nothing. 0:05:19.040 --> 0:05:21.440 I hesitate to use the phrase junk DNA because each 0:05:21.520 --> 0:05:24.080 year it seems we realize more of this junk is 0:05:24.120 --> 0:05:28.359 actually functional. Humans don't just share a high percentage of 0:05:28.360 --> 0:05:32.440 protein encoding genes with bananas. We also share eight of 0:05:32.440 --> 0:05:35.200 those genes with a mouse, and we share sixty one 0:05:35.640 --> 0:05:39.080 of disease causing genes with a fruit fly. Brodie said, 0:05:39.400 --> 0:05:42.200 the remarkable thing is that despite being very far apart 0:05:42.279 --> 0:05:45.600 in evolutionary time, we can still find a common signature 0:05:45.600 --> 0:05:48.839 in the genome of a common ancestor. These are preserved 0:05:48.880 --> 0:05:51.200 because the genome of an organism that lived billions of 0:05:51.279 --> 0:05:54.640 years ago contained genes that helped cells live and reproduce. 0:05:55.200 --> 0:05:59.719 Those same genes are preserved in us and plants. Francis 0:05:59.760 --> 0:06:02.320 add that humans likely share about one percent of their 0:06:02.360 --> 0:06:05.680 DNA with other fruits as well. He said this is 0:06:05.720 --> 0:06:08.000 because all life that exists on Earth has evolved from 0:06:08.040 --> 0:06:10.839 a single cell that originated about one point six billion 0:06:10.920 --> 0:06:19.560 years ago. In a sense, we're all relatives. Today's episode 0:06:19.560 --> 0:06:21.839 was written by Alia Hoyt and produced by Tyler Playing 0:06:22.240 --> 0:06:24.120 brain Stuff is the production of I Heart Radio's Has 0:06:24.120 --> 0:06:26.040 Stuff Works. For more in this and lots of other 0:06:26.040 --> 0:06:28.960 topics that are different but do similar things, visit our 0:06:29.000 --> 0:06:31.720 home planet how stuff Works dot com and for more 0:06:31.720 --> 0:06:33.720 podcasts from my heart Radio, you can visit the heart 0:06:33.800 --> 0:06:36.360 Radio app, Apple Podcasts, or wherever you listen to your 0:06:36.360 --> 0:06:37.080 favorite shows.