What is the Difference Between Point Mutations and Indels

The key difference between point mutations and indels is that point mutations are a type of mutation in a DNA sequence where a single nucleotide is changed due to change, addition, or deletion, while indels are the insertions or deletions of one or more nucleotides in the DNA sequence.

A mutation is a change in the DNA sequence of an organism resulting from the occurrence of errors in DNA replication during cell division. Mutations take place due to different mutagens that bring about a permanent change in the sequence of DNA. Mutations are of many types: somatic mutations, germline mutations, chromosomal alterations, point mutations, and frameshift mutations. Point mutations and indels are two types of gene mutations. They occur within the nucleotide sequence of a gene.

CONTENTS

1. Overview and Key Difference
2. What are Point Mutations 
3. What are Indels
4. Similarities – Point Mutations and Indels
5. Point Mutations vs Indels in Tabular Form
6. Summary – Point Mutations vs Indels

What are Point Mutations?

Point mutations are genetic mutations in which a single nucleotide base is altered from a DNA sequence of a genome due to a change, addition, or deletion of nucleotides. Point mutations have various effects on protein products. They may arise from spontaneous mutations that take place during DNA replication. Transition mutations are the replacement of purine bases with another purine or pyrimidine with another pyrimidine base. Transversion mutations happen when purine is replaced with a pyrimidine or vice versa.

Point mutations are of three types: nonsense, missense, and silent mutations. Nonsense mutations occur when a sense codon turns to a stop codon due to a substitution of a nucleotide. This results in truncated proteins upon protein expression. Missense mutations happen when the substitution of a nucleotide results in a change in a codon sequence. As a result, the corresponding amino acid changes, producing an altered protein at the end of the protein expression process. Silent mutations do not affect the protein function; however, a single nucleotide change and new codon specify the same amino acid, giving an unmutated protein. This is due to the degeneracy of the genetic code, where there are many codons coding for the same amino acid. Hence, no phenotypic change occurs in the organism even though the genotype is changed.

What are Indels?

Indels are a type of gene mutation where insertions and deletions occur in the nucleotide sequence of the DNA. Single nucleotides or multiple nucleotides are either added or removed from the DNA sequence, causing a change in the sequence. The key results of an indel are frameshift mutations, which cause a change in the open reading frame. This will result in altered proteins following transcription and translation.

Indels occur as insertion of bases and deletion of bases. During the deletion of bases, downstream bases get shifted to the left, and during the insertion of one or more bases, the downstream bases get shifted to the right. Typically, DNA is present with a proof-reading mechanism to avoid the occurrence of indels by a mutation through the introduction of stop codons. Indels cause the disruption of the reading frame. Disruption will result in the incorporation of different incorrect amino acids into the protein and result in an abnormal protein product. Indels will lead to disease conditions such as Tay-Sachs disease.

What are the Similarities Between Point Mutations and Indels?

• Point mutations and indels are two types of mutations.
• Moreover, they belong to the category of gene mutation.
• They alter the nucleotide sequence of DNA.
• Point mutations and indels may result in the production of non-functional proteins.
• Both mutations may lead to the occurrence of diseases.

What is the Difference Between Point Mutations and Indels?

Point mutation is a type of mutation that changes one of the nucleotides of the DNA sequence, while indel is the insertion and deletion of one or more nucleotides from the DNA sequence. Thus, this is the key difference between point mutations and indels. While point mutations alter only one nucleotide, indels change one or more than one nucleotide. Moreover, the main types of point mutations are silent, missense, and nonsense mutations, while the main types of indels are insertions and deletions.

The below infographic presents the differences between point mutations and indels in tabular form for side by side comparison.

Summary – Point Mutations vs Indels

A mutation is a change in the DNA sequence of an organism. Mutations take place due to different mutagens that bring about a permanent change in the sequence of DNA. Point mutation is a type of substitution where one of the nucleotides of the DNA is replaced. Indel is the insertion and deletion of nucleotides from the DNA sequence. Point mutations may occur as silent, missense, or nonsense mutations. So, this summarizes the difference between point mutations and indels.

Reference:

1. “Frameshift mutation / frame-shift mutation; frameshift.” News, Nature Publishing Group.
2. “Point Mutation.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.

Image Courtesy:

1. “Point mutations-en” By Jonsta247 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “CRISPR Cas editing” By Mjeltsch – Own work (CC BY-SA 4.0) via Commons Wikimedia