This document discusses mutagenesis, which is the process by which DNA changes, resulting in gene mutations. Mutations can be caused by DNA replication errors, DNA damage from mutagens like radiation or chemicals, or molecular genetic techniques. There are different types of mutations that can result in silent, missense, nonsense, or frameshift changes to proteins. Mutagenesis drives evolution by creating genetic variation but can also cause diseases. Common mutagens include radiation, UV light, chemicals, viruses and bacteria. The document provides examples of different mutations and diseases they can cause, like sickle cell disease and cystic fibrosis.

1. Mutagenesis
Dr. Asmita Daspute.
Assistant Professor
Dept. of Environmental Science,
SBES College Of Science, Aurangabad.

2. Introduction
• Mutagenesis is the process by which an organism's deoxyribonucleic acids (DNA)
change, resulting in a gene mutation.
• A mutation is a permanent and heritable change in genetic material, which can result in
altered protein function and phenotypic changes.
• DNA consists of nucleotides that contain a phosphate backbone, a deoxyribose sugar, and
one of four nitrogen-containing bases (adenine [A], guanine [G], cytosine [C], and
thymine [T]).
• DNA mutagenesis occurs spontaneously in nature or as a result of mutagens (agents with
a predisposition to alter DNA). Furthermore, molecular genetic techniques, such as
polymerase chain reaction (PCR), have revolutionized how mutations are obtained and
studied.
• Mutagenesis is the driving force of evolution; however, it can also lead to cancers and
heritable diseases.

3. • single base-pair substitutions are the most common cause of human pathology. ‘
• An example is sickle cell disease, where a single base-pair mutation results in glutamate to
valine amino acid substitution.
• Otherwise, human disease is a result of a mixed assortment of insertions, deletions,
duplications, inversions, expansions, fusions, and complex rearrangements.
• For example, a CGG repeat expansion in the FRM1 gene causes fragile X syndrome, while
a fusion protein BCR-ABL results in chronic myeloid leukemia
Introduction

4. Mutagenesis
• It is noteworthy that not all DNA mutations will have an impact on protein synthesis or function.
There are various types of mutations, such as silent, missense, nonsense, and frameshift mutations.
• A silent mutation is a nucleotide substitution that codes for the same amino acid; therefore, there is
no change in the amino acid sequence or protein function.
• A missense mutation is when a nucleotide substitution results in an amino acid change. Missense
mutations have variable effects but can lead to a decreased or altered protein function (e.g., sickle
cell disease).
• A nonsense mutation is when a nucleotide substitution results in a new stop codon, which includes
UGA, UAA, and UAG (remember the mnemonic "U Go Away, U Are Away, and U Are Gone,"
respectively). These protein products are truncated and frequently nonfunctional (e.g., cystic
fibrosis).
• A frameshift mutation occurs through the addition or deletion of nucleotides not divisible by 3,
resulting in the misreading of the downstream nucleotides. These proteins may be shorter or longer,
and protein function may be disrupted or altered (e.g., Duchenne muscular dystrophy).
• Other types of mutations exist outside of the coding sequence. These include splice site, promoter or
enhancer sequence, and termination site mutations. For example, in some forms of B-thalassemia,
a mutated splice site results in the use of cryptic splice locations, causing impaired B-globin
synthesis.

5. Mutagenesis
• Mutagenesis can arise by mis-replication (mis-incorporation
during DNA replication) or as the result of DNA modification
post-replication Spontaneous mutations are those that arise
during normal reproduction/growth; "induced" mutations are the
result of environmental mutagens including radiation and
chemicals.
• Examples of mutagens include radioactive substances, x-rays,
ultraviolet radiation, and certain chemicals.

6. Mutagenesis
• Three different types of common mutagens are observed in nature- physical
and chemical mutagens agents and biological agents
• Physical Agents: Heat and radiation.
• Chemical Agents: Base analogs.
• Biological Agents: Viruses, Bacteria, Transposons.

8. Mutation Causing Agents
• Ionising Radiation
• Ultraviolet light
• Chemicals
• Biological agents

9. Function
• Mutagenesis is the driving force behind evolution, and genetic variation is the
result of mutations.
• Any change in genetic information may result in advantageous or
disadvantageous phenotypic characteristics that impact an organism's fitness.
• When a mutation results in a higher fitness, natural selection favors these
phenotypes, and these traits are more likely to be passed to offspring.
• Mutagenesis occurs as a result of DNA replication errors, DNA damage, and lab
techniques. Here we will break mutagenesis down into endogenous and
exogenous causes.