Genes are segments of DNA that store information for the production of proteins or other molecules.
Proteins are the building blocks of life, and they perform various functions in the cell and the body. But how do genes turn into functions? This is where gene expression comes in.
Gene expression is the process of using the information in a gene to produce a protein or another molecule. Gene expression can be divided into two main steps: transcription and translation.
TRANSCRIPTION: Copying The Gene
Transcription is the first step of gene expression. It happens in the nucleus of the cell, where the DNA is located. In transcription, an enzyme called RNA polymerase reads a gene and makes a copy of it in the form of RNA.
RNA is a molecule similar to DNA but with some differences. For example, RNA has a single strand, while DNA has a double strand. RNA also has a different base than DNA; uracil instead of thymine.
The type of RNA that carries the information from a gene is called messenger RNA (mRNA). The mRNA leaves the nucleus and goes to the cytoplasm, where the next step of gene expression takes place.
TRANSLATION: Making The Protein
Translation is the second step of gene expression. It happens in the cytoplasm of the cell, where the ribosomes are located. Ribosomes are structures that make proteins by linking amino acids together. Amino acids are the building blocks of proteins, and there are 20 different types of them.
In translation, the mRNA attaches to a ribosome and delivers the message from the gene. The message is written in a code of four letters: A, U, C, and G. These letters represent the four bases of RNA: adenine, uracil, cytosine, and guanine. The code is read in groups of three letters, called codons. Each codon corresponds to an amino acid or a signal to start or stop translation.
To decode the message, another type of RNA is involved: transfer RNA (tRNA). The tRNA has two parts: one part has a codon that matches the mRNA, and the other part has an amino acid that matches the codon. The tRNA brings the amino acid to the ribosome and pairs with the mRNA. The ribosome then links the amino acid to the growing protein chain. This process continues until a stop codon is reached, and the protein is released.
REGULATION: Controlling Gene Expression
Not all genes are expressed all the time in all cells. Different cells have different functions, and they need different proteins to perform them. For example, muscle cells need proteins that help them contract, while nerve cells need proteins that help them transmit signals. Therefore, gene expression is regulated by various factors that can turn genes on or off, or increase or decrease their activity.
One way to regulate gene expression is by controlling transcription. Transcription can be influenced by molecules called transcription factors that bind to specific regions of DNA near a gene. These regions are called promoters, and they act as switches that turn transcription on or off. Some transcription factors activate transcription by helping RNA polymerase bind to the promoter, while others repress transcription by blocking RNA polymerase or changing the shape of DNA.
Another way to regulate gene expression is by controlling translation. Translation can be influenced by molecules that interact with mRNA or ribosomes. For example, some molecules can bind to mRNA and prevent it from attaching to ribosomes, while others can modify ribosomes and affect their activity. Translation can also be affected by factors that change the stability or degradation of mRNA.
Gene expression is a complex and dynamic process that allows cells to use their genetic information to produce functions. By understanding how genes turn into functions, we can learn more about how life works at the molecular level.
Researched by Olamide Opebiyi