Transcripción de ADN; traducción de ARN o síntesis de proteínas; explicado

In subjects such as biology, details of a phenomenon or process. . .

can be better understood if they are exposed in a logical way, transiting in a timely manner. . .

from the abstract to the concrete; or vice versa. All in a coherent context I will make an effort to achieve the above exposing in a basic way the process. .

. of DNA transcription and protein translation or synthesis Let's start explaining this topic by what do we know. .

. we know that DNA contains instructions to build a living being, right? But.

. . how does DNA become a living being?

The details in this regard overwhelm even the scientists, however. . .

the fundamental principle is the following: A fragment of the DNA is copied or transcribes into a molecule called ribonucleic acid or RNA for short It is from this copy that proteins are synthesized or produced Proteins are like the basic building blocks of a living being. . .

like Wally the cat, or like you or me The copy or transcription of DNA in RNA is done in the cell nucleus. . .

in the membrane core of the eukaryotic cell and in the nucleus without membrane of the prokaryotic cell. . .

but the translation or synthesis of proteins happens in a cellular structure called ribosome Here we see a pair of ribosomes in the cytoplasm Resembling perhaps an acorn, the ribosome is composed of two parts: one smaller than the other Here there are a lot of ribosomes in the prokaryotic cell The DNA is lodged in the nucleus and organizes in chromosomes like that of this eukaryotic cell For reasons I'm not going to list here. . .

the DNA of the nucleus can’t go directly to the cytoplasm. . .

but the DNA fragments transcribed in the form of RNA can come out of the nucleus. . .

. . .

and take the information or message to the cytoplasm It is very clear why this ribonucleic acid is called messenger RNA or mRNA Unlike DNA that is composed of two strands, RNA is a molecule of a single strand or chain of nucleotides Remember that each DNA nucleotide consists of a deoxyribose sugar. . .

a nitrogenous base and a phosphate group Deoxyribose is a sugar of five carbon atoms I'm pointing them with the laser indicator In chemistry, we number these carbons from the one that joins the nitrogenous base You see? We have five! The fifth and third carbon are two important extremes.

. . We call these extremes: 5 prime phosphate and 3 prime hydroxyl Here is the scheme of a nucleotide.

It has its ends five prime phosphate and three prime hydroxyl Other nucleotides are chained at these ends to form a strand of DNA In this way we have a strand in 5’-end and 3’-end direction By its molecular structure the other strands of DNA will necessarily have an. . .

inverse direction. DNA strands are antiparallel To copy a fragment of DNA in form of ARN it is enough to use a strand… of the first as a template ARN form their nucleotides with a ribose sugar and by this molecular reason one of its four nitrogenous bases differs from those of DNA RNA uses uracil as a nitrogenous base instead of DNA thymine But both bases are –let's say equivalents In addition to the number of strands, now you now other molecular differences between DNA and RNA I have given you some preliminary concepts But how is messenger RNA synthesized from a DNA template strand? The process of transcription is more complex in eukaryotic cells than in prokaryotic cells.

. . but to simplify it, I will explain it in a general way.

. . that is, with the essential points valid in both cases In transcription there is always an enzyme RNA polymerase.

. . that moves in 3'-end - 5'-end direction on the template thread I hope it makes more sense now.

. . why I first explained to you what the hell was that "3 prime end-5 prime end" In its path through the template strand, RNA polymerase builds the strand of messenger RNA How is it done?

Don't worry! Here I will show you I promise you that the explanation is coming. I was engrossed with the music.

. . and the dancing enzyme.

But first, I warn you that this enzyme can form. . .

different types of RNA All these types of RNA are important to build living beings from proteins But in the transcript, the protagonist is the messenger RNA The transcription or formation of messenger RNA has three stages: initiation, elongation and termination The initiation consists in indicating the RNA polymerase at which point of the ADN sequence. . .

it must initiate transcription or RNA synthesis There are sequences of nitrogenous bases - in DNA - called promoter centers that. . .

that indicate to this enzyme where to start the transcription or copy in the form of RNA Coming up next, let's see it in more detail! RNA polymerase binds to these promoter centers and forms a. .

. transcription bubble, where -in cooperation with other enzymes- begins. .

. to partially unwind the DNA molecule Here we see the unwound strands in the transcription bubble and I have added the letters of each nitrogenous bases. .

. to represent them better Remember that in DNA each of the nitrogenous bases of a strand matches a specific base of the other In DNA, bases couples are always adenine and thymine; guanine and cytosine The bases are united through bridges of hydrogen, but in the transcription. .

. these are broken by enzymatic action The unique RNA chain is constructed in the transcription bubble. .

. in the opposite direction to that of the template strand, that is. .

. in a direction from 5 prime to 3 prime, given that it is a kind of negative of the DNA strand template In the initiation stage, the RNA polymerase assembles the first RNA nucleotides or ribonucleotides. .

. because it uses ribose -remember- and these nucleotides are found there in the nucleus The enzyme selects those that correspond. .

. to each of the nitrogenous template bases I explained earlier that in RNA, uracil replaces thymine this means that when the RNA polymerase finds an adenine in the template strand. .

. places a ribonucleotide with uracil in the RNA strand When there are enough ribonucleotides and the RNA chain does not break. .

. the RNA polymerase is released from the promoter. .

. and the elongation happens In this phase, RNA polymerase continues its path through the template strand while assembling. .

. in the same way the rest of ribonucleotides In the back of the transcription bubble, the DNA template strand. .

. meets again with its original partner to re-form. .

. the double helix, as if it were the end of a «closure» Transcription continues until the RNA polymerase encounters a DNA termination signal. .

. and then the transcription bubble will. .

. disassembles and releases the RNA polymerase and newly formed messenger RNA And now what happens with the messenger RNA? Messenger RNA carries this information to ribosomes Ribosomes use messenger RNA to synthesize proteins in cooperation with transfer RNA The RNA message is encrypted.

. . in the famous genetic code, which is like a biological language.

. . The -between quotes- words in the genetic code are encrypted in a.

. . sequence of nitrogenous bases To form a word of this code a minimum of three nitrogenous bases is required This unit of three nitrogenous bases or triplet is called «codon» In protein synthesis, a codon can be translated into an amino acid or a start or.

. . termination signal for the translation process Several triplets or codons can encode the same amino acid and that is why it is said that there are synonymous codons.

. . The translation starts with the binding of the messenger RNA to the ribosome.

. . starting from a triplet or initiation codon that is usually adenine, uracil and guanine.

. . and which also encodes the amino acid «methionine» Note that the ribosome covers two codons of the messenger RNA that are going to.

. . attach to two transfer RNA The transfer RNA is.

. . say, like a piece of a puzzle At one end it coincides with a codon of mRNA.

. . and in the other end carries a specific amino acid It's like an amino acid transporter Each amino acid transported by the transfer RNA binds or chains with the next.

. . by a peptide bond When that happens the transfer RNA that transported it is free and can be used to transport the same type of amino acid.

. . in another protein synthesis We observe how the process continues chaining or linking.

. . amino acids transported by transfer RNA The ribosome goes through the codons of messenger RNA in.

. . 5 prime end - 3 prime end direction The translation process ends until you come across a.

. . codon of completion to which no amino acid corresponds, meaning that.

. . does not translate into any amino acid it's just an end signal At this point the ribosome separates from the messenger RNA and also the amino acids.

. . chain is free.

And so it ends the process of translation or synthesis. . .

because a protein is a long chain of amino acids that is folded. . .

or bent All right! You have reached the end of this video. If you have doubts with something of the exposed .

. . you can go back to the video, repeat it or pause it when you need it.

. . my presentation has been general and basic.

To deepen and encompass more details. . .

your participation is required. For example, you can investigate the. .

. differences of these processes in eukaryotic and prokaryotic cells or. .

. other factors or enzymes involved in transcription or translation but I didn't. .

. include in the video, as well as the 20 main amino acids that make up . .

. the proteins, and codons that encode them. I hope I have been helpful.

. . See you another time!