What is RNA and what is its function?
Written by Ysandra Prille A. Tabilon
Reviewed by Dr. Reuben J C. Los Baños, Ph.D.
Ribonucleic acid is one of the major biological macromolecules essential to life. It is a nucleic acid that is present in the majority of living organisms and viruses. It is famous for its role in synthesizing proteins in your body. It also replaces deoxyribonucleic acid as a carrier of genetic code in many viruses.
A central dogma of molecular biology asserts that genetic code flows from DNA to RNA to proteins. It is Deoxyribonucleic acid that makes RNA, and RNA makes the proteins needed for your body. In this role, it is Ribonucleic acid that plays the “DNA photocopy” of the cell.
Basic Structure and Composition of RNA
Nucleotides are the nucleic acid’s basic building blocks. Ribonucleic acid, together with DNA, is a polymer made of long chains of nucleotides. A nucleotide of an RNA consists of a sugar molecule called ribose. This sugar attaches itself to a phosphate group and a nitrogen-containing base.
RNA’s nitrogen bases include adenine, guanine, uracil, and cytosine. They consist of a long, single-stranded chain. But, there are some special RNA viruses that are double-stranded. The molecule can have a variety of lengths and structures.
Types of Ribonucleic Acid
There are various types of Ribonucleic Acid. But, the most well-known and studied in the human body are the following:
Messenger RNA (mRNA). It is a molecule produced as a result of transcription. It carries the genetic code from the nucleus to the ribosomes for protein synthesis. It then transmits instructions on the type of proteins your body cells need.
Transfer RNA (tRNA). It is a molecule that transfers amino acids to the ribosomes for protein synthesis. It also assists in the translation of an mRNA sequence to proteins. It does this by forming base pairs with its complementary sequence on the mRNA.
Ribosomal RNA (rRNA). It is the ribosome’s most essential and prevalent structural component for all organisms. This molecule is necessary for the synthesis and translation of mRNA into proteins.
Functions of Ribonucleic Acid
One of the main functions of RNA is to help in the translation of DNA into protein. When your cells need a certain protein, they activate the gene that codes for that protein. It then generates several copies of that genetic information in the form of mRNA.
The mRNA copies are then used to translate the genetic information to protein. It accomplishes this action via the ribosomes, the cell’s protein production machinery. Thus, it increases the quantity of a protein produced by a single gene. Also, it acts as a control point for determining the time and amount of protein produced.
Ribonucleic acid depending on its type, has a variety of functions within the cell. They act as structural molecules within the organelles of cells. They also have a role in the catalysis of biological reactions. Other functions of Ribonucleic Acid are the following:
- Carrier of genetic information all living cells
- In protein synthesis, it serves as an adapter molecule
- Intermediary between Deoxyribonucleic acid and ribosomes
- Assists the ribosomes in choosing the appropriate amino acid needed for protein synthesis.
- Act as enzymes (ribozymes) to speed chemical reactions
How is RNA created? What is RNA and what is its function?
Transcription is a process that converts DNA into Ribonucleic acid. It entails copying the gene sequence to create an RNA molecule. The primary enzymes involved in transcription are RNA polymerases. This enzyme synthesizes a complementary strand of RNA from a single-stranded gene template.
3 Stages of Transcription
Initiation. An RNA polymerase enzyme binds to a segment of DNA called the promoter. After binding, the double helix of DNA unwinds into a template strand and a non-coding strand. The single-stranded template is the one needed for transcription.
Elongation. The RNA polymerase reads the template strand in the 3′ to 5′ direction during this stage. Each nucleotide can synthesize a 5′-3′ RNA strand with complementary nucleotides. The newly synthesized RNA strand is almost identical to the non-coding strand. But, it contains the base uracil (U) instead of thymine (T).
Termination. RNA synthesis will continue until it comes across a signal instructing it to stop. Terminators are the sequences that signal that the transcript is complete. Once transcribed, they cause the RNA polymerase to release the transcript.
What came first protein or RNA?
The conflict between RNA and protein over who came first is analogous to the chicken or egg problem. Many people believe it is the RNA, while others believe it is the protein.
But if you consider the central dogma, it states that DNA generates RNA, which in turn makes proteins. So that implies that Ribonucleic Acid came first than proteins.
The dogma states that DNA contains the information needed to make your proteins. Ribonucleic acid serves as a messenger, conveying this information to the ribosomes. Translation refers to the process of converting ribonucleic acid to proteins.
According to the RNA world hypothesis, life on Earth evolved from a single RNA molecule. In this hypothesis, it says that this molecule evolved before DNA and proteins. It also says that it is capable of self-replication without the help of other molecules.
The general order has to be Ribonucleic acid first, then proteins, then DNA. Ribonucleic acid is like the ancestral molecule of life. Like deoxyribonucleic acid, RNA is capable of storing and replicating genetic information. Also, it can catalyze chemical reactions necessary for life, like protein.
Additionally, the well-known Urey-Miller experiment may reveal that proteins came first. Amino acids, the building blocks of protein, appeared to have formed during the early Earth’s formation.
The RNA-First scenario is quite popular among scientists studying the origins of life. But, there is insufficient evidence to explain what hypothesis is actually true.
What is the difference between RNA and DNA?
Deoxyribonucleic acid and Ribonucleic acid are nucleic acids. They both contain monomers called nucleotides. But, they, too, perform different functions and have distinct characteristics between them.
DNA has a role in the storage and transmission of genetic code needed for the formation of your other cells. While Ribonucleic acid transmits these codes to the ribosomes to synthesize proteins.
The location of DNA is in the nucleus, while some are present in the mitochondria. It is self-replicating and cannot leave its location. Meanwhile, RNA forms in the nucleolus and moves to the cytosol and ribosomes. Also, it gets synthesized from deoxyribonucleic acids.
DNA contains deoxyribose sugar, which is why it’s referred to as deoxyribonucleic acid. It also has two strands that twist to form a double helix. Meanwhile, RNA has ribose sugar hence the name ribonucleic acid. It only has a single strand of nucleotide, forming a helix.
They also differ in their sizes and helix geometry. DNA is way larger than RNA since it has millions of long-chain nucleotides that shape into a B-form helix. This increases the susceptibility of it to UV damage.
By contrast, Ribonucleic acid is much smaller. It has hundreds of shorter nucleotide chains that form into an A-helix. It also has a higher UV resistance than deoxyribonucleic acid.
Moreover, Ribonucleic Acid’s chemical structure is quite like that in DNA. Yet, both of them have some distinctions. DNA contains a sugar group with a 2′ hydrogen, while RNA contains a 2′ hydroxyl group.
DNA is stable under alkaline conditions due to its C-H bonds. While the O-H bond in RNA’s ribose makes it more reactive. That is why it is not stable under alkaline conditions. Also, due to the large grooves on its molecule, it is prone to enzyme attack compared to DNA’s smaller grooves.
Another key difference is their pyrimidine base and base pairing. They both contain four nitrogenous bases. But, deoxyribonucleic acid contains thymine that pairs with adenine. While Ribonucleic acid has the nucleobase uracil to pair with adenine.
Can RNA turn into DNA?
Ribonucleic acid can convert into deoxyribonucleic acid through a process called reverse transcription. This process is in contrast to the central dogma’s DNA-to-RNA flow. It is the reverse process of normal cellular respiration.
Reverse transcriptase is the enzyme that generates complementary DNA from an RNA template. This process is more prevalent and essential for retroviruses to be infectious. Reverse transcriptase was first discovered in retroviruses. But, new studies reveal that it is present in viruses, bacteria, animals, and plants.
An example of a retrovirus that uses reverse transcription is HIV. It can insert its genetic code into the genomes of infected cells. It replicates the HIV RNA and converts it to double-stranded DNA. It then incorporates itself into the cell’s DNA and orders the cell to replicate the virus.
Moreover, Thomas Jefferson University scientists were able to make history. They were the first to prove that mammalian cells can revert RNA segments to DNA. These findings could challenge the central dogma and have wide implications. This could imply that RNA messages can serve as templates for gene repair or rewriting.
Is RNA self replicating?
The replication of the genome is necessary for life to continue. One of the characteristics of living things is their potential for reproduction. You might be aware that Deoxyribonucleic acid is self-replicating, but what about RNAs?
According to the RNA world hypothesis, RNAs may be the first discovered molecule. This molecule has diverse functions like those of Deoxyribonucleic Acid. Ribozymes are small RNA structures that carry out chemical reactions necessary for life. Besides that, this enzyme might be able to replicate Ribonucleic acids.
Scientists have been attempting to recreate a self-replicating RNA to test this theory. So far, they only developed ribozymes capable of replicating only the straight strands. But, when folded, it is incapable of self-replication.
Yet, eventually, self-replication became possible. James Attwater has developed a ribozyme capable of replicating folded RNA strands. James isolated these ribozymes capable of replicating small segments of folded RNA. He then engineered the best version to replicate and create new full synthetic copies. This is the molecule’s first instance of self-replication.
For years, researchers have speculated that there might be a simpler way to copy RNA from DNA itself. Yet, now they have finally synthesized RNA enzymes capable of self-replication. Even in the absence of proteins or other components, these molecules can replicate.
Ribozymes are the ones that are self-replicating. Although, not all RNAs are self-replicating.
Can RNA exist without DNA? What is RNA and what is its function?
Deoxyribonucleic acid is the genome of all self-replicating cellular organisms studied thus far. Also, they perform all biological functions under the central dogma. As a result of this fact, almost all biologists must believe that no organism exists without DNA.
But, some scientists still believe that an organism devoid of DNA could exist on Earth. This type of organism may exist in the world of microorganisms. It is an area of enormous biological diversity. The majority of microorganisms still remain unidentified. If you think about it, anything is possible.
Scientists have devised experimental methods to identify organisms that lack DNA. They employed techniques that inhibit DNA replication or expression. They conducted it on 100 microbial samples collected from a variety of water sources. They were able to discover colonies and cells that appeared to be DNA-free. But, it turns out they were DNA-positive.
So far, no microorganism without Deoxyribonucleic acid has been identified. The findings reveal that there may be no such organisms or that they exist on Earth but are very difficult to find. Nonetheless, some scientists believe that these types of organisms exist in our environment.
So, to answer your question on the existence of RNA without DNA, there have been no findings of such organisms yet. The discovery of RNA organisms could alter our understanding of evolution and biology. It is likely to be an organism that has developed alone and is distinct from DNA organisms.
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