0:00 Armando Hasudungan biology and medicine videos, please make sure to subscribe, 0:06 join the former 0:06 group for the latest videos, please visit Facebook, Armando Hasudungan. 0:13 Now in this video we will look at an overview of transcription and translation 0:18 in cells. 0:19 It won't go into a whole lot of detail, but just so we get an idea of what is 0:23 happening. 0:25 So we begin by going inside a cell. 0:27 Here is the membrane of the nucleus, not the plasma membrane, but the nucleus, 0:33 where our 0:33 genetic material is stored. 0:35 And outside this nuclear membrane is the cytoplasm, which is the fluid within 0:41 the cell. 0:42 Now within the cytoplasm we find many things, including amino acids, and there 0:46 are many 0:47 types of amino acids, there are 20 in total. 0:52 Now going back inside the nucleus we can find our genetic material, which are 0:56 packaged 0:57 up into chromosomes, forming chromosomes. 1:00 We have 46 chromosomes in total, 23 pairs, one from each parent. 1:10 If we unpack this particular chromosome, the genetic material is cleverly 1:16 wrapped around 1:17 these proteins called histones. 1:20 So pulling out some of these histones, our genetic material here are organized, 1:26 wrapped 1:27 around these individual histones. 1:32 Our genetic material is called DNA, or long deoxyribonucleic acid. 1:41 If we unwind the DNA we can see that the DNA is double stranded and is made up 1:47 of nucleotides. 1:49 There are four types of nucleotides, which make up the DNA. 1:59 So what do we do with this DNA? 2:01 Well we can replicate it, and we do so during cell division called mitosis, and 2:06 I have a 2:07 video on that if you want to watch it, here. 2:13 Our DNA also contains many genes, genes are regions in the DNA that do things 2:19 for our 2:20 body. 2:21 For example, genes make templates for proteins and enzymes. 2:27 To make proteins and enzymes for our body, first the DNA has to make RNA, RNA 2:36 stands for 2:37 ribonucleic acid. 2:41 Our body makes RNA through the help of an enzyme called RNA polymerase. 2:48 Now RNA polymerase synthesizes an RNA using one of the DNA strands as a 2:56 template. 2:58 This process of synthesizing RNA from DNA is called transcription, because we 3:08 are transcribing. 3:11 RNA typically has a polyA tail, which means it has many adenosine nucleotide at 3:18 one end, 3:19 and on the other end there is a cap, and we'll talk about these features later 3:26 on. 3:27 This particular RNA that was synthesized by the RNA polymerase is a messenger 3:34 RNA, or 3:35 mRNA for short. 3:38 It is a pre-MRNA to be specific, because it has not been properly converted to 3:46 mRNA. 3:47 There are actually three major types of RNA in humans. 3:50 These are the messenger RNA, mRNA, transfer RNA, tRNA, and ribosome RNA, rRNA. 3:59 And they are all synthesized by different types of RNA polymerases. 4:03 You have RNA polymerase 1, 2, and 3, but we don't have to worry about that now. 4:08 Anyways, let's go back to the pre-MRNA that was just made. 4:15 So now we are focusing on messenger RNA. 4:20 The pre-messenger RNA, like all pre-RNAs, are made up of nucleotides as well. 4:30 They also contain regions called introns and axons. 4:35 The pre-MRNA then undergoes a process known as splicing. 4:41 Splicing is basically when the regions called introns are removed from the pre- 4:48 MRNA, but 4:49 the exons, they will stay. 5:00 And this will form a unique type of mRNA, and therefore a unique type of 5:09 protein. 5:10 So after splicing, after introns are removed, this will form an mRNA, still 5:16 with the polyA 5:18 tail at one end and a cap at the other. 5:22 Now the mRNA will then leave the nucleus through the nuclear pore and into the 5:26 cell cytoplasm. 5:31 So we know that the mRNA has something to do with making proteins, what does it 5:35 actually 5:36 do? 5:37 Well the mRNA serves as a template to form proteins. 5:42 mRNA is sort of like a foreign book that has to be translated to make proteins, 5:51 if that 5:51 made any sense. 5:53 Now let's just pause there with the mRNA and look at the other RNAs, because 5:53 they are 5:59 important as they participate in protein synthesis. 6:04 So let's go back to the nucleus to the DNA again. 6:08 A specific type of RNA polymerase can synthesize pre-TRNA, pre-transfer RNA, 6:14 through the process 6:15 called transcription. 6:17 The pre-TRNA is in splice to removing the introns and then you get a type of T 6:25 RNA. 6:26 The TRNA will then leave the nucleus to the nuclear pore into the cytoplasm. 6:31 The TRNA will actually fold up into a shape that looks sort of like this. 6:38 So what do we do with these TRNAs or what do the TRNAs do? 6:43 Well remember, the TRNA is made up of nucleotides, not amino acids. 6:51 And what TRNA actually do is that every TRNA will attach to one amino acid. 7:00 Remember in the cytoplasm there are amino acids. 7:08 See in the cytoplasm there is this enzyme called aminoacyl-TRNA synthetase. 7:15 So aminoacyl-TRNA synthetase essentially attaches an amino acid to a TRNA, 7:23 forming a TRNA with 7:24 an amino acid. 7:31 So now what we have in the cytoplasm is TRNA with different types of amino 7:36 acids. 7:37 Then we have an mRNA which is a template for the TRNA with the amino acid. 7:44 So what is missing? 7:46 Well the only thing that is missing is an enzyme that actually connects the two 7:50 , connects 7:51 the TRNA with the mRNA. 7:53 This enzyme is called a ribosome and a ribosome is made from our RNA, our last 8:01 type of RNA. 8:02 So let's go back to the nucleus and see how we form this ribosome. 8:06 But before that, please remember that all these RNA, TRNA and mRNA, they're all 8:12 RNAs, 8:13 they're all made up of nucleotides, not amino acids. 8:19 So we're back in the nucleus to form ribosomes. 8:22 We actually have to dig deeper into the nucleus, a region called the nucleolus. 8:28 Our DNA and the nucleolus have genes to make ribosomes. 8:33 A special RNA polymerase called RNA polymerase 1 will synthesize our RNA, ribos 8:43 ome our RNA. 8:45 And if I had not mentioned earlier, the RNA polymerase that synthesizes TRNA is 8:53 RNA polymerase 8:55 3. 8:56 Anyways, let's go back to the nucleolus, RNA polymerase 1 will synthesize pre-R 9:05 RNA, pre-ribosome 9:06 our RNA, which will be spliced to form two RRNA strands. 9:13 One is small and the other one is big. 9:16 The small and the big RRNA strands will eventually form the small and large sub 9:21 unit of the ribosome. 9:25 These strands will then leave the nucleolus where they will fold to form a 9:31 small and large 9:33 subunit of the ribosome. 9:35 The subunits are still termed pre-ribosome in the nucleus. 9:40 The pre-ribosome can then leave the nucleus into the cytoplasm. 9:46 Within the cytoplasm, the small and large subunit will attach to the cap end of 9:52 the mRNA, 9:54 like so. 9:55 So here we have a functioning ribosome with its large and small subunit 10:00 attaching to the 10:01 cap region of the mRNA. 10:10 The ribosome has three special sites within it, the EPA site. 10:18 Now each of these means something, but just for simplicity you can think of A 10:23 as attachment, 10:24 E as exit. 10:28 So anyways, the ribosome will move towards the poly A end of the mRNA, like so. 10:36 During its movement, the ribosome will act like a factory for protein synthesis 10:42 . 10:42 It will attach tRNA with mRNA essentially. 10:47 Remember, the tRNA is made up of nucleotides, so all these are nucleotides. 10:54 Three nucleotides down this end of the tRNA is special because it is what will 10:59 bind to 11:00 three nucleotides on the mRNA. 11:04 These three nucleotides are called codons in mRNA and anti-codons in tRNA. 11:13 So for example, if this tRNA anti-codon matches this codon of the mRNA, it will 11:22 bind on the 11:23 A site of the ribosome. 11:25 The ribosome will then keep moving and then the tRNA will then be on the P site 11:32 of the 11:33 ribosome. 11:36 The ribosome will release the amino acid from the tRNA in the P site. 11:41 And then as the ribosome keeps moving, the tRNA then will exit through the E 11:49 site. 11:50 The amino acid that was released from the tRNA will join with other amino acids 11:55 , from 11:56 other tRNAs, to form a polypeptide or protein. 12:01 Now this whole process is known as translation. 12:07 So what the ribosomes are doing is that the ribosomes are translating the mRNA 12:13 to make 12:14 proteins. 12:17 Now just for your interest, this protein that is just synthesized by the ribos 12:24 ome or any 12:25 other proteins for that matter can be broken down into amino acids again and 12:31 then the cycle 12:32 can continue. 12:34 What is important to understand here is that amino acids, tRNA, mRNA, and rRNA 12:41 are critical 12:42 in synthesizing proteins. 12:45 Also, many enzymes in our body are made up of proteins, they're proteins. 12:50 However, a ribosome is not made up of amino acids, it is made up of nucleotides 12:59 . 12:59 Quite unique. 13:02 Thank you for watching. 13:03 Hope you enjoyed this short overview on translation and transcription. 13:07 Bye.
