The document presents an internal assessment on mutations in protein coding genes, focusing on the history, types, and implications of genetic mutations. Key themes include the definitions and effects of point mutations, frameshift mutations, and splice site mutations, as well as case studies on diseases such as Huntington's disease and sickle cell anemia. Techniques to study these mutations and their relevance in personalized medicine and gene editing are also discussed.

1. GURU GHASIDAS VISHWAVIDYALAYA
DEPARTMENT OF BIOTECHNOLOGY
INTERNAL ASSESMENT PRESENTATION
( SESSION 2024-25 )
PRESENTED BY :
YUGESHVAR YADAV
M.SC. IN MICROBIOLOGY
FIRST SEMESTER.
GUIDED BY :
DR. ASHISH KUMAR
ASSOCIATE PROFESSOR
DEPARTMENT OF
BIOTECHNOLOGY.

2. MUTATION IN
PROTEIN
CODING GENES .

3. HISTORY OF MUTATIONS
• Germinal mutations
Seth Wright was the first to describe germinal mutations in domesticated
animals in 1791.
• Naming the term "mutation"
In 1901, Hugo de Vries named the seemingly new forms that appeared in
his experiments on the evening primrose as "mutations".
• Studying mutations
In 1910, Thomas Hunt Morgan began the scientific study of mutations by
experimenting on fruit flies. Morgan and his team treated fruit flies with
X-rays, acids, and other toxic substances to create mutant flies.

4. HISTORY OF MUTATIONS
• X-ray work on fruit flies
Muller's work on fruit flies using X-rays was a breakthrough in genetics.He
discovered that mutation rates could be increased by treating male fruit fly
sperm with high doses of X-Ray.
Herman Muller Hugo De Vries

5. Introduction to Genetic
Mutations
• DEFINITION : A genetic mutation is a change in the DNA sequence of
an organism.
• OVERVIEW : Mutations can significantly impact protein structure and
function by altering the primary, secondary, tertiary, and quaternary
structure, leading to changes in enzyme activity, protein-protein
interactions, protein-ligand interactions, and cellular localization.
Point mutations, frameshift mutations, and chromosomal
rearrangements can introduce steric hindrance, electrostatic changes,
and hydrophobic interactions, disrupting protein function.

6. Introduction to Genetic
Mutations
• Techniques such as X-ray crystallography, NMR spectroscopy,
molecular dynamics simulations, site-directed mutagenesis, and
biochemical assays help study mutational effects.
• RELEVANCE : Understanding these effects informs personalized
medicine, protein engineering, and gene editing, with implications for
diseases like sickle cell anemia, cystic fibrosis, and cancer,
highlighting the importance of protein structure-function relationships
in therapeutic applications.

7. Types Of Mutations
• POINT MUTATIONS :
i.Missense
ii.Non Sense
iii.Silent
• FRAMESHIFT MUTATION :
i.Insertion
ii.Deletion
• SPLICE SITE MUTATION
• OTHERS : Expansions like Trinucleotide Repeats.

8. Point Mutations
• A point mutation is a genetic alteration involving a change to a single
nucleotide within the DNA sequence. It can lead to alterations in
protein structure and function, which may result in phenotypic
consequences or disease.
• SUB TYPES : Missense
Nonsense
Silent Mutations.
LET US DEAL WITH THREE OF THEM IN DETAILS....

9. Missense Mutations
• A single nucleotide change results in the substitution of one amino
acid for another in the protein sequence.
• Example: Sickle cell anemia (GAG → GTG in the β-globin gene causes
a glutamic acid-to-valine substitution).
• Implications: Can be conservative (minimal impact on protein
structure) or non-conservative (significant impact due to changes in
charge, polarity, or size).

11. Non Sense Mutations
• A nonsense mutation is a point mutation where a single nucleotide
change in the DNA sequence converts a codon that codes for an
amino acid into a premature stop codon (e.g., UAG, UAA, or UGA).
This results in the termination of translation and the production of a
truncated, often nonfunctional protein.
• A single base substitution, typically from a purine (A or G) to a
pyrimidine (T or C), leads to the creation of a stop codon.
Example: CAG (codes for glutamine) → TAG (a stop codon).

12. Nonsense Mutations
Nonsense-Mediated Decay (NMD):
• If the premature stop codon occurs far upstream of the last exon-exon
junction, the mRNA is typically recognized as defective and degraded
by the nonsense-mediated mRNA decay pathway.
• NMD prevents the accumulation of truncated proteins that might be
harmful to the cell.

14. Silent Mutations
• A silent mutation is a type of substitution mutation where a
change in the nucleotide sequence does not result in a change in
the amino acid sequence of the protein. This occurs because the
genetic code is degenerate—multiple codons can encode the
same amino acid.
• For example:
Codons GAA and GAG both code for glutamic acid. Changing the
DNA sequence from GAA to GAG is a silent mutation.

16. Frameshift Mutations
• A frameshift mutation occurs when nucleotides are inserted or
deleted from the DNA sequence in a number that is not a multiple
of three. This disrupts the triplet codon reading frame of mRNA
during translation, altering the downstream amino acid sequence
and often leading to the production of a truncated or
nonfunctional protein.
• Also Called InDel Mutation.
• TYPES : Insertion And Deletion.

17. Frameshift Mutation
• Insertion:
Addition of one or more nucleotides into the coding sequence.
Example: Adding a single adenine (A) in the sequence AUG-GCU →
AUG-AGC-U (disrupting the reading frame).
• Deletion:
Removal of one or more nucleotides from the coding sequence.
Example: Deleting one nucleotide from AUG-GCU → AUG-CU (shifts
the reading frame).

18. Frameshift Mutation
Resulting Effects:
• Alters all codons downstream of the mutation site.
• Frequently leads to the creation of a premature stop codon.
• Often activates nonsense-mediated mRNA decay (NMD) to
degrade the defective mRNA.

19. Frameshift Mutation
• Loss of Function: Truncated proteins often lose critical functional
domains, rendering them nonfunctional.
• Gain of Toxic Function: In some cases, altered proteins may
aggregate or interfere with normal cellular processes.
• Haploinsufficiency: If one allele is affected, the remaining allele
may not produce enough functional protein to maintain normal
cellular function.
• Frameshift mutations can extend the protein sequence into
noncoding regions, potentially disrupting downstream genes or
regulatory elements.

21. Splice Site Mutation
• A splice site mutation occurs when a nucleotide change affects
the conserved sequences at the intron-exon junctions or
regulatory regions critical for the removal of introns during pre-
mRNA splicing.
• These mutations can disrupt the normal recognition of splice
sites by the spliceosome, leading to aberrant mRNA and protein
products.

23. Trinucleotide Repeat Expansions
Trinucleotide repeat expansions are mutations where a sequence of
three nucleotides (e.g., CAG, CGG, GAA) is repeated more times than
normal in a specific region of a gene.
When the number of repeats exceeds a threshold, it can lead to
disease due to:
• Loss of function of the gene.
• Toxic gain of function at the RNA or protein level.

24. Trinucleotide Repeat Expansions
• Coding Region Expansions:
Typically encode polyglutamine (polyQ) tracts due to CAG repeats.
Diseases: Huntington’s disease, spinocerebellar ataxias.
Mechanism: Toxic gain of function at the protein level (misfolding
and aggregation).
• Non-Coding Region Expansions:
5' UTR: Fragile X syndrome (FMR1, CGG repeats).
Intron: Friedreich’s ataxia (FXN, GAA repeats).
3' UTR: Myotonic dystrophy type 1 (DMPK, CTG repeats).
Mechanism: RNA toxicity, epigenetic silencing, or sequestration of
RNA-binding proteins.

26. Disorders From Mutation
• Huntington's disease is an autosomal dominant
neurodegenerative disorder caused by a CAG trinucleotide repeat
expansion in the HTT gene, leading to an elongated polyglutamine
(polyQ) tract in the huntingtin protein.
• This results in toxic protein aggregation, neuronal dysfunction,
and cell death, primarily in the striatum and cortex.

27. Disorders From Mutation
HTT Gene:
• Located on chromosome 4 (4p16.3).
• Encodes the huntingtin protein, involved in intracellular transport,
signaling, and transcriptional regulation.
CAG Repeat Expansion:
• Normal range: ≤26 repeats.
• Intermediate range: 27–35 repeats (may expand in offspring).
• Pathogenic range: ≥36 repeats.
• Reduced penetrance: 36–39 repeats.
• Full penetrance: ≥40 repeats.

28. Disorders From Mutation
Motor Symptoms:
• Early: Subtle clumsiness, twitching, and fidgeting.
• Late: Chorea (involuntary jerky movements), dystonia(muscle
contract), and rigidity.
Cognitive Decline:
• Progressive impairment in memory, executive function, and
problem-solving.
• Eventually leads to dementia.

29. Disorders From Mutation
Psychiatric Symptoms:
• Depression, anxiety, irritability, and obsessive-compulsive
behaviors.
• High risk of suicide.
Disease Progression:
• Symptoms typically begin between ages 30–50.
• Duration from onset to death is approximately 15–20 years.

30. Case Study Of Sickle Cell Anemia
Gene:
Mutation in the HBB gene, which encodes the β-globin subunit of
hemoglobin, located on chromosome 11p15.5.
Mutation:
Single-nucleotide substitution (GAG → GTG) in codon 6 of the HBB
gene.
Results in the replacement of glutamic acid with valine in the β-
globin chain (p.Glu6Val).

31. Case Study Of Sickle Cell Anemia
Impact on Hemoglobin Structure:
Alters the structure of hemoglobin A (HbA), converting it to
hemoglobin S (HbS).
HbS polymerizes under low oxygen conditions, forming rigid fibers
that distort red blood cells into a "sickle" shape.

34. THANK YOU..!!