The key difference between gene and genome is that gene is a specific fragment of DNA that codes for a protein while genome is the entire collection of DNA of an organism that contains the entire genetic information.
Each species has a unique set of inherited characteristics that make them different from each other. Usually, these characteristics are encoded in the DNA (deoxyribonucleic acid) molecules present in their cells. Gene properties and genome properties vary widely from one species to another. Moreover, gene and genome are two terms associated with DNA. Gene is the basic unit of heredity, and it is a specific fragment of DNA of a chromosome that contains the genetic code to produce a protein. The whole set of chromosomes represent the genome of an organism, and it is located inside the nucleus of eukaryotes.
CONTENTS
1. Overview and Key Difference
2. What is Gene
3. What is Genome
4. Similarities Between Gene and Genome
5. Side by Side Comparison – Gene vs Genome in Tabular Form
6. Summary
What is a Gene?
Genes are the elements of heredity that determine the inherited characteristics from parent to offspring. The existence of genes and their transmitting processes were first suggested by Gregor Mendel. He called genes as ‘factors’ and found out that most of the factors or heredity elements pass from parents to offspring. However, Mendel did not know about DNA. Later scientists discovered DNA as the main genetic material in organisms.
Figure 01: Gene
Genes are specific DNA fragments or segments. These specific segments are capable of controlling specific heredity characteristics. Genes express and produce proteins. Gene expression occurs via two major steps: DNA transcription and translation. In sexual reproduction, offspring obtain one copy of each gene from both parents. Gene has two variants called alleles. In simple words, alleles are the different forms of a gene. A single allele or several alleles are responsible for controlling certain characteristics in the organisms.
What is Genome?
In general, the total DNA content in a single cell is known as the ‘genome’ of the organism. It is true for many organisms, but some viruses only contain RNA. Hence, in these viruses, the total quantity of RNA represents their genomes.
In modern molecular biology, the genome is the entire quantity of heredity information. Thus, it includes both genes and non-coding sequences of DNA/RNA. The term ‘genome’ can also refer to specific genetic contents. For example, the total content of the nuclear DNA in a cell is referred to as the nuclear genome while the total DNA content in mitochondria is referred to as the mitochondrial genome. In addition, genome may also comprise of non-chromosomal genetic elements such as viruses, plasmids, and transposable elements.
Figure 02: Genome
Genomics is the study area that analyzes the properties of the genomes. Evolution of the genome can be identified with the help of genome composition, which includes genome size and proportions of non-repetitive and repetitive DNA. If we consider the human genome, it contains 23 chromosomes. Out of 23, only one chromosome is a sex determinative while the remaining 22 chromosomes are autosomal chromosomes. There are approximately 20,000 to 25,000 genes in the human genome. To identify and map the sequence of chemical base pairs which make up the human DNA, there is an international project going on since 1990 called ‘The Human Genome Project’
What are the Similarities Between Gene and Genome?
- Gene and genome carry the genetic information of an organism.
- Thus, DNA is the main constituent of genes and genome.
- In eukaryotes, genes and genome are found inside the nucleus.
- However, in prokaryotes, genome and genes are present in the cytoplasm.
- Besides, the building block of both genes and genome is the deoxyribonucleotides.
What is the Difference Between Gene and Genome?
Gene is a segment or a portion of the DNA molecule while genome is the total DNA content in a cell. So, this is the key difference between gene and genome. Furthermore, coding also contributes to the difference between gene and genome. That is; the genes code for specific proteins. But, genome itself cannot code for proteins as it contains almost all the DNA. Moreover, the genome consists of all the base pairs in a cell while gene consists of only a few base pairs as it represents only a DNA segment. Therefore, this is also a difference between gene and genome.
Furthermore, a difference between gene and genome is the study area. The study of properties of genes is referred to as ‘genetics’ while the study of properties of the genome is referred to as ‘genomics’. Besides, in general, an organism has one genome, but it has thousands of millions of genes in that particular organism. Hence, this is also a major difference between gene and genome.
Summary – Gene vs Genome
Genome refers to the total amount of DNA in a cell. There are thousands of genes in one genome. Gene is a specific DNA fragment or segment that codes for a protein. It consists of genetic information to produce a specific protein. Hence, gene is the basic structural and functional unit of heredity. Both gene and genome are made from DNA. Thus, this is the summary of the difference between gene and genome.
Reference:
1. Mandal, Ananya. “What Are Genes?” News, 26 Feb. 2019, Available here.
2. “GENOMES.” GNN – Genome News Network, Available here.
Image Courtesy:
1. “Gene expression” By Genomics Education Programme (CC BY 2.0) via Flickr
2. “Phage injecting its genome into bacteria” By phage:Adenosine, bacteria + composition: Thomas Splettstoesser (www.scistyle.com) – Own work (CC BY-SA 3.0) via Commons Wikimedia