Central Dogma - Online Tutor, Practice Problems & Exam Prep

The central dogma of biology describes the unidirectional flow of genetic information from DNA to protein, encompassing two key processes: transcription and translation. Transcription synthesizes messenger RNA (mRNA) from DNA, while translation converts mRNA into proteins. This process is irreversible; once nucleic acid information is transformed into protein, it cannot revert to DNA. Additionally, reverse transcription allows RNA to synthesize DNA in specific scenarios. Understanding these mechanisms is crucial for grasping gene expression and the fundamental principles of molecular biology.

Central Dogma

In this video, we're going to begin our lesson on central dogma. And so the central dogma of biology refers to the unidirectional flow of biochemical information from DNA to protein. And so by unidirectional, what we mean is that it is a one-directional flow since the root uni means 1. And so information, biochemical information, will flow from DNA to protein. But because it's a one-directional flow, the biochemical information cannot flow backwards from protein to DNA. Now, this unidirectional flow of biochemical information from DNA to protein turns out is a 2-step process that we have numbered down below, number 1 and number 2. And so the first step of the process is called transcription, which is the process that builds RNA by using DNA as the coding template. Now, as we move forward in our course, we're going to learn more about the process of transcription. However, the specific type of RNA that's going to be built in this case is going to be messenger RNA, which is also known as mRNA. And so we'll learn a lot about messenger RNA or mRNA as we move forward through our course. Now in the second step of this process is translation, and translation is the process that builds protein by using the encoded messages of RNA, specifically mRNA or messenger RNA, which, again, we'll learn more about moving forward in our course. Now, sometimes the process of transcription and translation are collectively referred to as gene expression. And so a gene is a small unit of DNA, recall from our previous lesson videos. And in order, for a gene to be expressed, its final product needs to be created, which in many cases, the final product will be a protein. And so if we take a look at our image down below, we can get a better understanding of this central dogma of molecular biology, which is, again, the unidirectional flow of biochemical information from DNA all the way to protein. And so, of course, what you can see here is that, the process that uses DNA to build RNA is going to be transcription. So this is labeling, the arrow that goes in this direction. And, of course, the second step of the process is going to be translation. And translation is the process that uses the RNA to build a protein. And so, again, the specific type of RNA that's going to be used in translation is called mRNA or messenger RNA, which we'll get to learn more about as we move forward in our course. Now it is important to note that DNA can be replicated as we talked about in our previous lesson videos. DNA replication is the process of using DNA as the template to build even more DNA. And so it's kind of like a cycle between DNA. And so DNA replication here, which we can add replication, of course, is possible. Also, what is possible is a process that's referred to as reverse transcription, which is the process of using RNA, and using the RNA to build DNA. So RNA can be reverse transcribed into DNA, and so that is referring to this backwards arrow right here. The process of using the messenger RNA to build DNA is possible in some scenarios, and this is called reverse transcription. And so what you can see here is that DNA can be used to build RNA, and RNA can be used to build DNA. And, of course, translation is the process that converts the messages of RNA into a protein. However, notice that this process here is unidirectional. It goes in one direction only. And so, the transfer of nucleic acid to protein is irreversible. And so, of course, the nucleic acids include DNA and RNA, but once nucleic acid information has been converted-to-protein, this process here is irreversible, and information from protein is not used to build nucleic acids. And so that is partly what the central dogma is referring to as well. And so this here concludes our brief introduction to the central dogma of biology and how it involves both transcription and translation. And as we move forward in our course, we're going to learn a lot more about each of these processes, transcription and translation. So I'll see you all in our next video.

According to the central dogma, what is the intermediate molecule involved in the flow of information in a cell that should go in the blank? DNA → ________ → Proteins

• A. Ribosome.
• B. rRNA.
• C. mRNA.
• D. tRNA.

The full process by which genotype becomes expressed as phenotype is called:

• A. Transcription.
• B. Translation.
• C. DNA Replication.
• D. Gene expression.

Here’s what students ask on this topic:

What is the central dogma of molecular biology?

The central dogma of molecular biology describes the unidirectional flow of genetic information from DNA to protein. This process involves two key steps: transcription and translation. During transcription, DNA is used as a template to synthesize messenger RNA (mRNA). In the subsequent step, translation, the mRNA is used to build proteins. This flow of information is irreversible, meaning that once genetic information is converted into protein, it cannot revert back to nucleic acids. Understanding this concept is fundamental for grasping gene expression and the mechanisms of molecular biology.

What are the steps involved in the central dogma?

The central dogma involves two main steps: transcription and translation. In transcription, DNA serves as a template to synthesize messenger RNA (mRNA). This mRNA carries the genetic information from the DNA to the ribosome, where translation occurs. During translation, the mRNA is read by the ribosome to assemble amino acids into a polypeptide chain, forming a protein. These steps ensure the flow of genetic information from DNA to protein, which is crucial for cellular function and gene expression.

What is the role of mRNA in the central dogma?

Messenger RNA (mRNA) plays a crucial role in the central dogma of molecular biology. During transcription, mRNA is synthesized from a DNA template. This mRNA then carries the genetic information from the DNA in the nucleus to the ribosome in the cytoplasm. In the ribosome, the mRNA is read during the process of translation to assemble amino acids into a specific sequence, forming a protein. Thus, mRNA acts as an intermediary, conveying genetic information from DNA to the protein synthesis machinery.

Can genetic information flow from protein back to DNA?

No, genetic information cannot flow from protein back to DNA. The central dogma of molecular biology states that the flow of genetic information is unidirectional, from DNA to RNA to protein. Once the information is converted into protein, it cannot revert back to nucleic acids. However, in specific scenarios, RNA can be reverse transcribed back into DNA, a process known as reverse transcription. This exception does not violate the central dogma's principle that information does not flow from protein to nucleic acids.

What is reverse transcription and when does it occur?

Reverse transcription is the process by which RNA is used as a template to synthesize DNA. This process is catalyzed by the enzyme reverse transcriptase. Reverse transcription occurs in specific scenarios, such as in retroviruses like HIV, where the viral RNA genome is reverse transcribed into DNA, which then integrates into the host genome. This process is an exception to the central dogma's unidirectional flow of genetic information, allowing RNA to be converted back into DNA.