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Mutations

Mutations

Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. Mutations can be characterized in a number of different ways: whether and how they alter the amino acid sequence of the protein, whether they occur over a small or large area of DNA, and whether they occur in somatic cells or germline cells.
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...

Mutations

Mutations

Spontaneous and Induced Mutations

Spontaneous and Induced Mutations

Spontaneous mutations arise infrequently during DNA replication due to errors in the process. A key factor behind these errors is tautomeric shifts in nitrogenous bases, where bases transition from keto to enol forms or amino to imino forms. This shift can alter base-pairing rules, leading to mutations. Additionally, reactive oxygen species (ROS) arising from aerobic metabolism can damage DNA, resulting in depurination (loss of a purine base) or depyrimidination (loss of a pyrimidine base).

Mutations in Microorganisms

Mutations in Microorganisms

Mutations are heritable changes in an organism’s genome involving alterations in the base sequence of DNA or RNA. These changes can influence cellular processes and phenotypic traits, potentially transforming the unaltered wild type into a mutant form. Such changes, termed forward mutations, are pivotal in shaping the genetic diversity of organisms.RNA viruses exhibit the highest mutation rates due to the absence of robust proofreading mechanisms during genome replication. In contrast,...

Point and Frameshift Mutations

Point and Frameshift Mutations

Point mutations are genetic alterations involving the change of a single nucleotide base pair in DNA. Depending on how the alteration affects protein synthesis, they can lead to various consequences.Point mutations fall into the following types:Silent mutations occur when a nucleotide change does not alter the amino acid sequence due to the redundancy of the genetic code. For instance, changing ACC to ACA still encodes threonine, leaving the protein function unaffected. This occurs because...

Translesion DNA Polymerases

Translesion DNA Polymerases

Translesion (TLS) polymerases rescue stalled DNA polymerases at sites of damaged bases by replacing the replicative polymerase and installing a nucleotide across the damaged site. Doing so, TLS allows additional time for the cell to repair the damage before resuming regular DNA replication.
TLS polymerases are found in all three domains of life - archaea, bacteria, and eukaryotes. Of the different classes of TLS polymerases, members of the Y family are fitted with specialized structures that...

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Related Experiment Video

Updated: Mar 30, 2026

DNAzyme-dependent Analysis of rRNA 2’-O-Methylation

DNAzyme-dependent Analysis of rRNA 2’-O-Methylation

Published on: September 16, 2019

Sequence Mutation and Structural Alteration Transform a Noncatalytic DNA Sequence into an Efficient RNA-Cleaving

Laura Chan¹, Kha Tram¹, Rachel Gysbers^1,2

¹Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main St. W., Hamilton, ON, L8S 4K1, Canada.

Journal of Molecular Evolution

|November 5, 2015

Summary

Directed molecular evolution and in vitro selection optimized a DNAzyme

Keywords:

8–17 DNAzyme In vitro selection Molecular evolution RNA cleavage

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Site-Directed Mutagenesis for In Vitro and In Vivo Experiments Exemplified with RNA Interactions in Escherichia Coli

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Published on: February 5, 2019

Area of Science:

Biochemistry
Molecular Biology
Synthetic Biology

Background:

DNA sequences can be engineered into catalytic DNA (DNAzymes) with RNA-cleaving abilities.
Further optimization of DNAzyme catalytic activity is achievable through in vitro selection.

Purpose of the Study:

To investigate the optimization of DNAzyme catalytic activity using in vitro selection.
To identify sequence variations and structural modifications that enhance DNAzyme function.

Main Methods:

In vitro selection applied to a partially randomized DNA library.
Bioinformatic analysis of isolated DNAzyme variants.
Activity assays of DNAzyme-substrate constructs.

Main Results:

Several DNAzyme variants with significantly improved catalytic activity were isolated.
Three key mutations were identified, leading to the 8-17 DNAzyme.
Further mutations enabled structural fine-tuning for specific RNA cleavage.

Conclusions:

Directed molecular evolution combined with in vitro selection effectively enhances DNAzyme catalytic efficiency.
The study highlights the potential for engineered DNAzymes to mimic natural enzyme evolution.