Central Dogma: Videos & Practice Problems

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

Central Dogma

In this video, we're going to begin our lesson on central dogma. The central dogma of biology refers to the unidirectional flow of biochemical information from DNA to protein. By unidirectional, what we mean is that it is a one-directional flow since the root uni means 1. Biochemical information will flow from DNA to protein. Because it's a one-directional flow, the biochemical information cannot flow backwards from protein to DNA. This unidirectional flow of biochemical information from DNA to protein turns out to be a 2-step process that we have numbered down below, number 1 and number 2. The first step of the process is called transcription, which builds RNA by using DNA as the coding template. 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. We'll learn a lot about messenger RNA or mRNA as we move forward through our course.

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. Sometimes the processes of transcription and translation are collectively referred to as gene expression. A gene is a small unit of DNA. 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. 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 the unidirectional flow of biochemical information from DNA all the way to protein. The process that uses DNA to build RNA is going to be transcription. The second step of the process is going to be translation. Translation uses the RNA to build a protein. The specific type of RNA that's going to be used in translation is called mRNA, which we'll get to learn more about as we move forward in our course.

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. It's kind of like a cycle between DNA. DNA replication here, which we can add replication, of course, is possible. What is also 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. RNA can be reverse transcribed into DNA, and this is referring to this backwards arrow right here. The process of using messenger RNA to build DNA is possible in some scenarios, and this is called reverse transcription. You can see here that DNA can be used to build RNA, and RNA can be used to build DNA. Translation is the process that converts the messages of RNA into a protein. Notice that this process here is unidirectional. It goes in one direction only. The transfer of nucleic acid to protein is irreversible. Once nucleic acid information has been converted to protein, this process is irreversible, and information from protein is not used to build nucleic acids. That is partly what the central dogma is referring to as well.

This here concludes our brief introduction to the central dogma of biology and how it involves both transcription and translation. As we move forward in our course, we're going to learn a lot more about each of these processes, transcription and translation. 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.

Answer: (C)

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

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

Answer: (D)

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 RNA to protein. This process involves two main steps: transcription and translation. During transcription, DNA is used as a template to synthesize messenger RNA (mRNA). In translation, the mRNA is then used to build proteins. This flow of information is irreversible, meaning that once the genetic information is converted into protein, it cannot revert back to nucleic acids. Understanding the central dogma is fundamental for studying molecular biology and genetics.

What are the steps involved in the central dogma?

The central dogma involves two key steps: transcription and translation. In transcription, DNA serves as a template to synthesize messenger RNA (mRNA). This process occurs in the nucleus of eukaryotic cells. The second step, translation, occurs in the cytoplasm where the mRNA is used to build proteins. Ribosomes read the mRNA sequence and translate it into a specific sequence of amino acids, forming a protein. These steps collectively are known as gene expression, where the genetic information in DNA is ultimately expressed as functional proteins.

What is the role of mRNA in the central dogma?

Messenger RNA (mRNA) plays a crucial role in the central dogma of molecular biology. It acts as an intermediary between DNA and protein synthesis. During transcription, mRNA is synthesized from a DNA template. This mRNA then carries the genetic information from the nucleus to the cytoplasm, where it is read by ribosomes during translation. The ribosomes use the sequence of codons in the mRNA to assemble amino acids into a specific protein. Thus, mRNA is essential for transferring genetic information from DNA to the protein-making machinery of the cell.

Can the flow of genetic information go from RNA to DNA?

Yes, the flow of genetic information can go from RNA to DNA through a process called reverse transcription. This process is catalyzed by the enzyme reverse transcriptase, which synthesizes DNA from an RNA template. Reverse transcription is not part of the central dogma's typical flow but occurs in specific scenarios, such as in retroviruses like HIV. These viruses use reverse transcription to integrate their RNA genomes into the host's DNA, allowing them to replicate within the host cell.

Why is the process of translation considered irreversible?

The process of translation is considered irreversible because once the genetic information in mRNA is used to synthesize a protein, it cannot be converted back into nucleic acids (DNA or RNA). This unidirectional flow ensures that the information encoded in nucleic acids is faithfully translated into functional proteins without the possibility of reverting to its original form. This irreversibility is a key aspect of the central dogma, emphasizing the one-way transfer of genetic information from DNA to RNA to protein.