Understanding Gene Mutations and Their Impact on DNA Sequences

 
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Mutation = change(s) in the nucleotide/base sequence of DNA; may occur due to errors in
Mutation = change(s) in the nucleotide/base sequence of DNA; may occur due to errors in
DNA replication or due to the impacts of chemicals or radiation to the DNA molecule
DNA replication or due to the impacts of chemicals or radiation to the DNA molecule
 
Mutation may result in coding sequences for new amino acids in proteins or not!
Mutation may result in coding sequences for new amino acids in proteins or not!
 
Mutations can occur due to errors during DNA replication (
Mutations can occur due to errors during DNA replication (
replication-dependent
replication-dependent
mutations)
mutations)
Mutations can also occur independently of DNA replication (
Mutations can also occur independently of DNA replication (
replication-independent
replication-independent
mutations)
mutations)
Mutagens, such as UV rays and chemicals, can cause mutations
Mutagens, such as UV rays and chemicals, can cause mutations
May occur in somatic or germ-line cells:
May occur in somatic or germ-line cells:
Somatic mutations
Somatic mutations
 are not inherited and thus play no major role in evolution
 are not inherited and thus play no major role in evolution
In cases of antibody formation and malignant transformation, somatic mutations are significant
In cases of antibody formation and malignant transformation, somatic mutations are significant
Only
Only
 germ-line mutations
 germ-line mutations
 are inherited and thus are important in evolution
 are inherited and thus are important in evolution
A:
 
Base substitution
 
A base substitution usually leads to base pair
substitution
GGG  AGT  GTA  GAT  CGT
CCC  TCA  CAT  CTA  GCA
CCC  TCA  CAT  CTA  GCA
GGG  AGT  G
C
A  GAT  CGT
 
A base substitution
CCC  TCA  C
G
T  CTA  GCA
GGG  AGT  G
C
A  GAT  CGT
GGG  AGT  GTA  GAT  CGT
CCC  TCA  CAT  CTA  GCA
 
First cycle of DNA replication
 
 
 
Base substitution is of two types:
 
 
Transition:
 
Purine is replaced with a purine
 
 
 
 
Pyrimidine is replaced with a pyrimidine
 
 
 
Transversions:
A purine is replaced by a pyrimidine
 
or a pyrimidine is replaced by a purine
 
Insertions & deletions
 
Silent mutation
 
Due to redundancy of Genetic Code, no change in amino acid sequence is produced!!
 
Missense mutation
 
Missense mutation produces a change in amino acid sequence in protein product
(Histidine in for Arginine); may change function of protein or may not!
 
Nonsense mutation
 
Bad news! – nonsense mutation produces a STOP codon within the mRNA transcript
leading to a truncated protein.  How short the protein product depends on where the
STOP codon was produced within the mRNA transcript.
 
Thank You
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Gene mutations are changes in the nucleotide sequence of DNA, leading to potential amino acid alterations in proteins. These mutations can occur due to replication errors or external factors like chemicals and radiation. Different types of mutations, such as base substitutions, transitions, transversions, insertions, and deletions, can affect genetic information differently. While some mutations are silent with no amino acid changes, others like missense mutations can alter protein function. Understanding these mutations is crucial in studying evolution and genetic diseases.


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  1. Gene Mutation Gene Mutation

  2. Mutation = change(s) in the nucleotide/base sequence of DNA; may occur due to errors in DNA replication or due to the impacts of chemicals or radiation to the DNA molecule Mutation may result in coding sequences for new amino acids in proteins or not! Mutations can occur due to errors during DNA replication (replication-dependent mutations) Mutations can also occur independently of DNA replication (replication-independent mutations) Mutagens, such as UV rays and chemicals, can cause mutations May occur in somatic or germ-line cells: Somatic mutations are not inherited and thus play no major role in evolution In cases of antibody formation and malignant transformation, somatic mutations are significant Only germ-line mutations are inherited and thus are important in evolution

  3. A: Base substitution mutated base

  4. A base substitution usually leads to base pair substitution GGG AGT GTA GAT CGT CCC TCA CAT CTA GCA GGG AGT GCA GAT CGT A base substitution CCC TCA CAT CTA GCA First cycle of DNA replication GGG AGT GCA GAT CGT CCC TCA CAT CTA GCA CCC TCA CGT CTA GCA GGG AGT GTA GAT CGT

  5. Base substitution is of two types: Transition: Purine is replaced with a purine A G G A Pyrimidine is replaced with a pyrimidine C T C T

  6. Transversions: A purine is replaced by a pyrimidine A C T C T A G G or a pyrimidine is replaced by a purine C G A G A C T T

  7. Insertions & deletions

  8. Silent mutation Due to redundancy of Genetic Code, no change in amino acid sequence is produced!!

  9. Missense mutation Missense mutation produces a change in amino acid sequence in protein product (Histidine in for Arginine); may change function of protein or may not!

  10. Nonsense mutation Bad news! nonsense mutation produces a STOP codon within the mRNA transcript leading to a truncated protein. How short the protein product depends on where the STOP codon was produced within the mRNA transcript.

  11. Thank You

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