RNA (ribonucleic acid) molecules are an important part of cellular function. There are several kinds of RNA and they are all involved in translating DNA gene codes into protein. Proteins play many vital functions within a cell, such as transportation, structure, and catalysis. Without RNA, proteins would not exist. Two of the more important kinds of RNA are messenger RNA (mRNA) and transfer RNA (tRNA). To understand how mRNA and tRNA are related, here is a flowchart that briefly summarizes protein synthesis.
DNA mRNA protein
In the first step, mRNA is created as a copy of a DNA segment. This DNA segment encodes a polypeptide, the backbone of a protein. DNA is too large to circulate around the cell and the information it contains must be preserved. mRNA is the solution to getting gene information to other parts of the cell. The process of creating mRNA is called transcription. mRNA is a single-stranded molecule containing nucleotides. This is in contrast to DNA which generally is a double-stranded molecule containing nucleotides. mRNA looks like a single piece of string floating around freely.
As the mRNA migrates around the cell it eventually encounters a ribosome. The ribosome and the mRNA join together to form a complex. The ribosome can then read the mRNA nucleotides in sets of three. Each three nucleotides read is a codon. For each codon there is a complementary tRNA.
tRNA is a single-stranded molecule like mRNA except it is shaped to look like the letter “t.” It is about 70 to 95 nucleotides long. mRNA, on the other hand, can be thousands of nucleotides long. Each tRNA has a specific anticodon and an attachment site for the amino acid that corresponds to the anticodon. Amino acids do not attach directly to mRNA.
mRNA and tRNA meet together at the ribosome. This is because mRNA attracts tRNA with the codon/anticodon interaction. At this point the ribosome takes the amino acid from the tRNA and then releases the tRNA. The next codon on the mRNA is read and the process is repeated with the next tRNA that is attracted to that specific codon. This process is called translation.
In summary these two types of mRNA are similar in that they both work together in protein synthesis. They are both copied from segments of DNA. They are both single-stranded molecules and they both contain the nucleotides adenine (A), cytosine (C), guanine (G), and uracil (U). However, they are different in fundamental ways.
Table summary: Differences between mRNA and tRNA
Property
mRNA
tRNA
Structure
Has no set shape
Shaped like a ‘t’, is more 3-dimensional than mRNA
Amino acid attachment
Cannot attach to amino acid
Can attach to an amino acid, has a special attachment site
Length/Number of nucleotides
Can be thousands of nucleotides long
Is only about 70 to 95 nucleotides long
Codons/Anticodons
Contains several codons
Each tRNA has one anticodon
Purpose
Is read directly for protein synthesis instructions. Polypetide (protein) sequence is taken directly from mRNA sequence.
Is read indirectly to attach to amino acid and to transfer said amino acid to the mRNA-ribosome complex
