Main Difference – Gene vs Protein

Gene and protein are two functionally-related entities found in the cell. Generally, genes are pieces of DNA. DNA is the genetic material of most organisms. DNA is transcribed into mRNA; mRNA translated into proteins is collectively known as the central dogma of molecular biology. Hence, genes are responsible for the production of proteins inside the cell. The main difference between gene and protein is that gene is responsible for the determination of the amino acid sequence of a functional protein whereas protein serves as a structural, functional, and regulatory component of the cell.

Key Areas Covered

1. What is a Gene
     – Definition, Structure, Role
2. What is a Protein
     – Definition, Structure, Role
3. What are the Similarities Between Gene and Protein
     – Outline of Common Features
4. What is the Difference Between Gene and Protein
     – Comparison of Key Differences

Key Terms: Amino Acids, Coding Sequence, Gene, Gene Expression, Protein, Regulatory Sequence

What is a Gene

A gene refers to a region (locus) of a chromosome that encodes a specific protein. A gene is identified as the molecular unit of heredity. The modern concept of the gene originated from the studies on the inheritance of characteristics by Gregor Mendel in 1860s. Typically, human genome consists of about 20,000 genes.

The structure of a gene consists of two segments: coding sequence and regulatory sequence. Coding sequence consists of exons and introns in eukaryotic genes. Prokaryotes lack introns that interrupt the coding sequence of a particular protein. Hence, prokaryotic genes are shorter than eukaryotic genes. In eukaryotes, introns are removed at consequent splicing of exons during the protein synthesis. Thus, multiple proteins can be produced by alternative splicing of the coding sequence of a single gene in eukaryotes. The coding sequence of a gene is flanked by untranslated regions (5’ UTR and 3’ UTR). The regulatory sequence of a gene consists of a promoter region, enhancers, and inhibitors. In prokaryotes, a group of functionally-related genes forms an operon. An operon has multiple protein-coding sequences, which are transcribed together. Some viruses are completely made up of RNA genomes. The production of the amino acid sequence of a functional protein is known as gene expression. Gene expression can be regulated at either transcriptional level or translational level. Their genes are called RNA genes. The structure of a eukaryotic gene and gene expression are shown in figure 1.

Figure 1: Eukaryotic Gene Expression

Organisms inherit a complete set of genes from their parents during reproduction. Mutations of a particular gene give rise to variants of the same gene known as alleles. Alleles produce variations of the trait of the gene inside a population. Alleles are either dominant or recessive alleles. Most alleles undergo Mendelian inheritance.

What is a Protein

A protein is a large nitrogenous organic compound, composed of one or two amino acid chains. Hence, the building blocks of a protein are amino acids. A protein is made up of an alternative assembly of universal amino acids. Peptide bonds are formed between amino groups and carboxyl acid groups of adjacent amino acids, forming a sequence of amino acids. Therefore, proteins are called polypeptides. This means protein is a polymer. Typically, a polypeptide consists of 50 – 2000 amino acids. The primary protein structure is shown in figure 2.

Figure 2: Primary Protein Structure

Protein synthesis occurs as a result of gene expression. Transcription and translation are the two steps of protein synthesis. The study of the structure and function of these proteins is called proteomics. However, proteins are a very complex and dynamic type of molecules. A typical protein consists of four structural levels: primary, secondary, tertiary, and quaternary. Different combinations of amino acids give different properties to proteins. Humans have of 20,000 to 25,000 protein-coding genes. About 2 million of different protein types can be synthesized from them. However, the human body contains around 50,000 proteins. The rest of the proteins are consumed through the diet. The four structural levels of a typical protein are shown in figure 3.

Figure 3: Structural Levels of a Protein

The two forms of a protein in the food are complete proteins and incomplete proteins. A complete protein consists of all the twenty essential amino acids while an incomplete protein only has some of them. These proteins are broken down into amino acids during digestion, and amino acids are transported to the cells via blood. Proteins are a structural component of a cell. They also regulate the functions of the body by acting as hormones and enzymes. They also serve as transporting molecules. For example, hemoglobin is the protein that transports oxygen throughout the body. Proteins produce molecules of the immune system as well.

Similarities Between Gene and Protein

• Gene and protein are two entities found inside the cell.
• Both gene and protein are functionally-related.
• Both gene and protein are important for the function of the cell.

Difference Between Gene and Protein

Definition

Gene: A gene is a region (locus) of a chromosome that encodes a specific protein.

Protein: A protein is a large nitrogenous organic compound, composed of one or two amino acid chains.

Significance

Gene: A gene is a piece of DNA or RNA.

Protein: A protein is a polypeptide.

Composition

Gene: A gene is made up of DNA nucleotides or RNA nucleotides.

Protein: A protein is made up of amino acids.

Responsible for

Gene: Gene is responsible for the determination of the genotype.

Protein: Protein is responsible for the determination of the phenotype.

Function

Gene: A gene is responsible for the production of a functional protein.

Protein: A protein serves as a structural, functional, and regulatory component of the cell.

Conclusion

Gene and protein are two entities found inside the cell. A gene is a piece of DNA made up of nucleotides. Genes are encoded for functional proteins. Proteins serve as a structural, functional, and regulatory component of the cell. Proteins are made up of amino acids. The main difference between gene and protein is the role of each entity inside the cell.

Reference:

1.“What is a gene? – Genetics Home Reference.” U.S. National Library of Medicine, National Institutes of Health, Available here.
2.“What are proteins and what do they do? – Genetics Home Reference.” U.S. National Library of Medicine, National Institutes of Health, Available here.

Image Courtesy:

1. “Gene structure eukaryote 2 annotated” By Thomas Shafee – Shafee T, Lowe R (2017). “Eukaryotic and prokaryotic gene structure”. WikiJournal of Medicine 4 (1). DOI:10.15347/wjm/2017.002. ISSN 20024436. (CC BY 4.0) via Commons Wikimedia
2. “Protein primary structure” By National Human Genome Research Institute -(Public Domain) via Commons Wikimedia
3. “Protein-structure” By NHGRI – Courtesy: National Human Genome Research Institute (Public Domain) via Commons Wikimedia

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