Difference Between Pseudogene and Gene

The key difference between pseudogene and gene is that pseudogene is a nonfunctional genetic element that does not code for a protein while gene is a functional genetic element that codes for a protein,

A genome is an organism’s complete set of genetic instructions that is very important to control the different characters (phenotype). Each genome contains all the information needed to synthesize essential molecules and build organisms. The genome consists of DNA. Genes are the specific sections of DNA. They code for proteins. By definition, a gene is a basic physical and functional unit of an organism that contributes to each individual’s physical features. A pseudogene is a defective copy of a functional gene that accumulates during evolution.

CONTENTS

1. Overview and Key Difference
2. What is a Pseudogene
3. What is a Gene
4. Similarities Between Pseudogene and Gene
5. Side by Side Comparison – Pseudogene vs Gene in Tabular Form
6. Summary

What is a Pseudogene?

A pseudogene is a nonfunctional segment of DNA that resembles a functional gene. In fact, it is a superfluous copy of a functional gene. It can be created directly by DNA duplication or indirectly by reverse transcription of an mRNA transcript. A pseudogene can be identified through genome sequence analysis. Typically, it lacks regulatory elements, which are very important for translation and transcription. Bacterial genomes contain many pseudogenes as many as functional genes. Different biological processes create pseudogenes. There is no specialized mechanism to remove them from the genome. Ultimately, pseudogenes may be deleted from the genome from chance replication or DNA repair errors. Otherwise, they accumulate different mutations over time, becoming no longer recognizable as former genes.

Sometimes, pseudogene sequence can be transcribed into RNA at a low level due to promoter elements. These promoter elements are inherited from either an ancestral gene or a new mutation. Although most of these transcripts of pseudogenes have no functional significance, some give rise to beneficial regulatory RNAs and new proteins.

What is a Gene?

Gene is the basic physical and functional unit of heredity. Genes are made up of DNA. Every functional gene has components such as promoter, start codon, stop codon, introns, exons, 3′ untranslated region, 5′ untranslated region and upstream elements, etc. These components are very important for the functionality of each gene. A gene has instructions to produce a molecule known as a protein. These molecules control different traits. In humans, genes’ size varies from a few hundred DNA bases to more than 2 million bases. The human genome project concluded in 2003 identified 20000 to 25000 human genes.

Every person has two copies of each gene. An allele is one of two or more versions of a gene. If the alleles are the same, the individual is homozygous for that gene (AA or aa). If the alleles are different, the individual is heterozygous for that gene (Ab). The term allele is originally used to describe variation among genes. Scientists continue giving unique names for genes. For example, the CFTR gene, a gene on chromosome 7,  has been associated with cystic fibrosis disease.

What are the Similarities Between Pseudogene and Gene?

• Both are present in the genome.
• Structurally, they are sections of DNA.
• They are inheritable genetic elements.
• They are subject to mutations.
• Both can work as oncogene or tumour suppressors.

What is the Difference Between Pseudogene and Gene?

A pseudogene is an inheritable genetic element that is nonfunctional as it does not code for a protein. On the other hand, a gene is an inheritable genetic element that is functional as it does code for a specific protein. So, this is the key difference between pseudogene and gene. Furthermore, a pseudogene lacks key regulatory elements, which are very important for translation and transcription. In contrast, a gene has all key regulatory elements that are very important for translation and transcription. Thus, this is another significant difference between pseudogene and gene.

The below infographic shows the differences between pseudogene and gene in tabular form.

Summary – Pseudogene vs Gene

The genome consists of a complete set of genes or genetic material present in a cell or organism. It contains a huge number of genes that control the phenotype of an individual. According to Human Genome Project, humans do have 20000 to 25000 genes. A pseudogene is an inheritable genetic element that is nonfunctional as it does not code for a specific protein. The gene is an inheritable genetic element, and it is the basic physical and functional unit of the inheritance. Thus, this is the summary of the difference between pseudogene and gene.

Reference:

1. “Pseudogene.” Pseudogene – an Overview | ScienceDirect Topics, Available here.
2. Pearson, Helen. “What Is a Gene?” Nature News, Nature Publishing Group, 24 May 2006, Available here.

Image Courtesy:

1. “AVP Gene Structure Diagram” (CC0) via Commons Wikimedia
2. “Pseudogene defects” By Rosieredfield – Own work (CC BY-SA 4.0) via Commons Wikimedia