Types of RNA and the Process of Transcription

RNA stands for ribonucleic acid. It helps in protein-making. There are many types of RNA in a cell. The main types of RNA are mRNA, tRNA, and rRNA. Each type of RNA has a different role in the cell. These types of RNA work together during protein synthesis. The different types of RNA play key roles in the molecular basis of inheritance.

This Story also Contains

1. What Is RNA?
2. RNA Types Table
3. Messenger RNA (mRNA)
4. Ribosomal RNA (rRNA)
5. Transfer RNA (tRNA)
6. Small Nuclear RNA (snRNA)
7. MicroRNA (miRNA)
8. Other Kinds Of RNA
9. The Video Recommended for Types Of RNA
10. MCQs on types of RNA

In biology, RNA in genetics helps to understand how traits are passed from parents to children. It shows how genes are turned on or off. The functions of RNA are key to gene regulation and gene expression. Messenger RNA (mRNA) carries the genetic code from DNA to the ribosomes. Transfer RNA (tRNA) helps assemble amino acids into proteins. Ribosomal RNA (rRNA) is part of the ribosome's structure and function. The different types of RNA help in medicine and genetics. RNA structure is simple, but its shape allows it to perform many functions.

What Is RNA?

Ribonucleic acid or RNA is one of the most important biomolecules functioning in the biological universe. RNA acts as the carrier of genetic information. It is involved in the process of genetic coding, decoding, regulation, and manifestation. It is single-stranded and exists in different types. Among them are the messenger RNA (mRNA), the transfer RNA (tRNA), and the ribosomal RNA (rRNA), all of which play different vital roles in protein synthesis and other major biological processes. Unlike DNA, which keeps the information for the more distant future, RNA is involved in more dynamic functions in the cell.

RNA is not as stable and is principally located in the cytoplasm of eukaryotic cells. However, the primary purpose of RNA is to be directly involved in the actual process of translation, or the process of building proteins using the code contained inside the DNA. Such versatility supports the significance of RNA within the gene regulation and gene expression process, thereby reaffirming RNA’s role as a critical component of any organism.

RNA Types Table

There are different types of RNA, each with a specific function in the cell. Some RNAs, like mRNA, tRNA, and rRNA, are directly involved in making proteins. Others, like miRNA, siRNA, and lncRNA, help regulate gene activity. Understanding the types of RNA is important to know how genetic information flows in the central dogma of molecular biology.

Messenger RNA (mRNA)

It is the RNA that carries the genetic message from the DNA to the ribosome for protein synthesis.

mRNA Structure

• It is a single-stranded molecule and has a structure that is capped at 5'- and tailed at 3' - with a poly-A tail at the 5'-end.

mRNA function

• It carries a genetic message from DNA to the ribosome; this message will be read by the ribosome for protein synthesis.

• It is a template used in the translation stage of protein synthesis for the assembly of amino acids into proteins.

mRNA Synthesis (Transcription)

• It is a product of a process of transcription in which RNA polymerase transcribes the DNA.

• Before there is any translation, this mRNA can undergo processing in which it is modified through a process known as capping, splicing, and polyadenylation.

Applications of mRNA

• It is used in mRNA vaccines, such as those for COVID-19.

• It has potential use in gene therapy and other biotechnological applications.

Ribosomal RNA (rRNA)

Another primary cellular component that plays a critical role in the creation of proteins is the ribosome.

rRNA Structure

• Makes up the ribosome along with proteins that help the rRNA form the ribosome, along with proteins

• It is of different sizes, 18S and 28S.

rRNA Functions

• Forms peptide linkages among amino acids.

• Supplies the right orientation between messenger RNA and transfer RNA during protein synthesis.

rRNA Genes and Ribosomal Structure

• The rRNA genes are transcribed to produce the ribosomal units.

• The construction of ribosomes is dependent on the availability of rRNA as well as ribosomal assembly.

Clinical Significance

• Antibiotics can impede protein synthesis in prokaryotes by attacking ribosomal RNA.

• Diseases, including ribosomopathies, are caused by defects attributed to mutations of the rRNA genes.

Transfer RNA (tRNA)

It performs the role of carrying amino acids into the ribosome while synthesising proteins.

Structure of tRNA

• The secondary structure is cloverleaf and has an anticodon loop and an amino acid binding site.

Functions Of tRNA

• The appropriate amino acid is brought in by pairing the anticodon of tRNA with the mRNA codon.

• It translates the genetic code into proteins.

Aminoacylation of tRNA (charging)

• The aminoacyl-tRNA synthetase charges the tRNA with an amino acid.

• Accurate synthesis of proteins is possible only when tRNA is charged.

Clinical Significance of tRNA

• Mitochondrial diseases may occur due to a mutation in tRNA.

• Applied in synthetic biology in the development of new kinds of proteins.

Small Nuclear RNA (snRNA)

snRNA is essential for the splicing of pre-mRNA as part of the process of maturation of mRNA.

Structure and Composition of snRNA

• Small RNA molecules combine with proteins to create spliceosomes.

• Schematic of snRNA in a spliceosome.

The function of snRNA

• Allows for the removal of introns from pre-mRNA.

• Ensures the splicing takes place properly, for proper formation of mRNA.

Varieties of snRNA

• Includes U1, U2, U4, U5, U6, each with a specific function in splicing.

• Each kind assists in recognising the splice sites and, therefore, catalyses the act of splicing.

Clinical Relevance of snRNA

• Splicing errors can cause genetic anomalies.

• snRNA is currently being researched as a possible target for therapy.

MicroRNA (miRNA)

miRNAs are small non-coding RNAs that function to block gene expression by binding to mRNA, causing their degradation or translating inhibition.

Structure Of miRNA

• Small RNA molecules produced from long precursors, known as pri-miRNA, are a shorter sequence of RNAs.

• Regulates gene expression after it is transcribed.

• Combined with complementary sequences of the mRNA, represses translation or activates degradation.

Clinical Relevance Of miRNA

• It is involved in many diseases, especially cancer.

• Therapeutic potentials exist with the manipulation of the expression of the gene with the help of miRNA mimics or inhibitors.

Diagrams: Types Of RNA

Other Kinds Of RNA

Apart from mRNA, rRNA, and tRNA, there are other important types of RNA in the cell. These non-coding RNAs do not make proteins but still play key roles in gene regulation and cellular functions.

Small Interfering RNA

• Small, double-stranded RNA plays a role in RNA interference.

• Used in gene silencing and research applications.

Long Non-Coding RNA (lncRNA)

• Non-coding RNAs are the longer RNA molecules that do not code for proteins.

• Function in gene regulation, chromatin remodelling, and in processes of diseases.

Ribozymes And Catalytic RNA

• Molecules of RNA with enzymatic activity.

• Participate in RNA splicing and reactions of self-cleavage.

The Video Recommended for Types Of RNA

MCQs on types of RNA

Question: Which type of RNA is used to carry genetic information copied from DNA?

1. mRNA

2. snRNA

3. rRNA

4. tRNA

Answer: Messenger RNA (mRNA) is the type of RNA that contains genetic information that has been copied from DNA. Transcription is the process by which DNA is converted into mRNA when a cell wants to produce a protein. After that, the mRNA moves to the ribosomes in the cytoplasm from the nucleus which houses the DNA. The ribosomes construct proteins using the information contained in the mRNA. Thus, mRNA serves as a messenger, transporting the genetic instructions from DNA to the cell's protein-making locations.

Hence, the correct answer is option 1)mRNA.

Question: Which RNA carries the amino acids from the amino acid pool to mRNA during protein synthesis?

1. rRNA

2. mRNA

3. tRNA

4. hnRNA

Answer: Transfer RNA or tRNA is crucial for the creation of proteins. During translation, it transports amino acids to the mRNA from the amino acid pool. An anticodon is a unique component of each tRNA molecule that aligns with the mRNA's codon. This makes it more likely that the protein being produced will include the appropriate amino acid.

Hence, the correct answer is option 3)tRNA.

Question: Which one of the following also acts as a catalyst in a bacterial cell?

1. 23S rRNA

2. 5S rRNA

3. snRNA

4. hnRNA

Answer: The bacterial ribosome contains 23S rRNA. It has peptidyl transferase catalytic activity, which aids in the creation of peptide bonds throughout protein synthesis. hnRNA stands for heterogeneous RNA, and snRNA stands for small nuclear RNA. 5s RNA is a constituent of the ribosome's big subunit. In bacterial ribosomes, 23S rRNA plays a pivotal role in the translation process, facilitating the formation of peptide bonds between amino acids. Peptidyl transferase, a catalytic function of 23S rRNA, is responsible for linking amino acids together during protein synthesis. Heterogeneous nuclear RNA (hnRNA) is the precursor to mRNA, undergoing processing before becoming mature mRNA in eukaryotic cells. Small nuclear RNA (snRNA) is involved in splicing, ensuring the removal of introns from pre-mRNA. Additionally, 5S rRNA, a component of the ribosome's large subunit, contributes to ribosomal stability and translation efficiency.

Hence, the correct answer is option 1) 23S rRNA

Also Read:

• MCQs on types of RNA

• RNA Processing

• RNA Splicing