What Is RNA?
Before we begin to talk about translation and transcription, we must first understand what RNA is. RNA strands for Ribonucleic Acid. Sound familiar? That's because RNA is almost just DNA without the "deoxy-".
RNA is similar to DNA, except that it is only single stranded, and instead of the nucleotide Thymine, RNA contains the nucleotide Uracil. Uracil is complementary to Adenine (similar to how Thymine was complementary to Adenine).
There are many forms of RNA, the three main types we will mention as we explore translation and transcription are mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA).
RNA is similar to DNA, except that it is only single stranded, and instead of the nucleotide Thymine, RNA contains the nucleotide Uracil. Uracil is complementary to Adenine (similar to how Thymine was complementary to Adenine).
There are many forms of RNA, the three main types we will mention as we explore translation and transcription are mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA).
One thing that is never mentioned when translation and transcription is taught is why these processes even need to happen in the first place. The answer is: proteins. When you think of proteins, you probably think of meats and dairy, and how much protein is in those food items. However, proteins are much more complex and abundant than you would think. Life processes are governed by different proteins.
Organisms use proteins to build and repair tissue, to make enzymes, to synthesize chemicals, to create pumps that keep concentration gradients. Proteins are important on the microscopic and macroscopic level. Proteins inside the cell are responsible for actions such as creating new organelles and digesting old ones, helping to facilitate cell replication, or repairing the cell membrane. Proteins on a larger level help build bone, muscle, tissue, cartilage, and blood. Proteins are everywhere, and they do almost everything. They are one of the most important components of any cell.
Genetics are regulated by proteins. If the DNA inside of you codes for a protein that produces black hair color, then your hair will be black. Viruses take over the cell so they can make viral proteins. Without proteins, organisms would not be able to function at the cellular level. The processes of translation and transcription is to take the genetic coding for proteins in DNA and turn the code into functional proteins.
Organisms use proteins to build and repair tissue, to make enzymes, to synthesize chemicals, to create pumps that keep concentration gradients. Proteins are important on the microscopic and macroscopic level. Proteins inside the cell are responsible for actions such as creating new organelles and digesting old ones, helping to facilitate cell replication, or repairing the cell membrane. Proteins on a larger level help build bone, muscle, tissue, cartilage, and blood. Proteins are everywhere, and they do almost everything. They are one of the most important components of any cell.
Genetics are regulated by proteins. If the DNA inside of you codes for a protein that produces black hair color, then your hair will be black. Viruses take over the cell so they can make viral proteins. Without proteins, organisms would not be able to function at the cellular level. The processes of translation and transcription is to take the genetic coding for proteins in DNA and turn the code into functional proteins.
Transcription
Translation is the process of getting RNA (mRNA to be specific) from DNA. DNA, while being extremely stable, cannot be used to make proteins because they are too big to exit the nuclear envelope of the nucleus. DNA also has segments called introns, which are segments that do not code for anything, and are therefore not useful for protein making (exons are segments of DNA that do code for proteins).
In transcription, an RNA polymerase enzymes and a number of accessory proteins called transcription factors make a new molecule from the DNA template. Transcription factors bind to specific DNA sequences called enhancer and promoter regions in order to recruit RNA polymerase to the appropriate starting transcription site. Together, the transcription factors and RNA polymerase form a complex called the transcription initiation complex. This complex acts as a machine that initiates transcription, and the RNA polymerase begins mRNA synthesis by matching complementary bases to the original DNA strand. This complex uses free floating nucleotides to construct a single stranded mRNA molecule that's complementary to the DNA template. Once this mRNA molecule is finished, it exits the nucleus and goes towards the ribosomes.
Think of transcription as transcribing. When you transcribe something, you put information into a written form, like DNA to mRNA.
In transcription, an RNA polymerase enzymes and a number of accessory proteins called transcription factors make a new molecule from the DNA template. Transcription factors bind to specific DNA sequences called enhancer and promoter regions in order to recruit RNA polymerase to the appropriate starting transcription site. Together, the transcription factors and RNA polymerase form a complex called the transcription initiation complex. This complex acts as a machine that initiates transcription, and the RNA polymerase begins mRNA synthesis by matching complementary bases to the original DNA strand. This complex uses free floating nucleotides to construct a single stranded mRNA molecule that's complementary to the DNA template. Once this mRNA molecule is finished, it exits the nucleus and goes towards the ribosomes.
Think of transcription as transcribing. When you transcribe something, you put information into a written form, like DNA to mRNA.
Diving DeeperAt the end of transcription, mRNAs undergo a 3' poly-Adenylation process where a string of Adenosines are attached to one end (its 3' end to be specific). This is called a poly-A tail. This poly-A tail prevents the mRNA from degradation and actually guides this molecule to the nuclear pore and outside the nucleus.
Proteins, lipids and etc can get to specific parts of the cell where they are needed because they are encoded with a tag that directs them there. The Poly-A tail acts as such as tag. |
Translation
After mRNA exits the nucleus, it goes to the ribosomes (the protein making centers of the cell). Ribosomes are made up of proteins and rRNA (ribosomal RNA). It enters the ribosome through one end, the ribosomes reads the codons (groups of three nucleotides) and tRNA (transfer RNA) molecules brings the appropriate amino acid to ribosome.
The amino acids form a chain, called a polypeptide chain, which is eventually separated from the ribosome and develops into a new protein. Think of ribosomes as factories that manufacturing of proteins take place, and tRNA as the workers who bring the necessary materials to assemble into proteins. It is hard to visualize the process of translation since many factors are active at the same time. The short videos below will help you visualize the process better. When you're trying to remember which process is which, remember that when you translate a language, you are turning one language into another. It's the same thing with the process of translation: you're turning the language of the blueprint (mRNA) into the language of proteins. |
Transcription |
Translation |