Understanding Mutations in Biology

 
MUTATIONS
 
 
In biology, a 
mutation
 is an alteration of the
nucleotide sequence 
of the genome of an
organism
May occur in 
somatic cells 
(aren’t passed to
offspring)
May occur in 
gametes
 (eggs & sperm) and be
passed to offspring
 
Mutations can:
-
 
be bad, leading to 
cancer, aging, birth
defects, self-aborted embryos
 
CACGTGGACTGAGGA
CTC
CTC
Codon for CTC =
glutamate
 
 
CACGTGGACTGAGGA
CAC
CTC
Codon for CAC =
valine
 
What does it matter???
 
 
 
 
-
be good, making an organism survive better
in its environment
-
Example: 
bacteria becoming antibiotic-resistant
 
The ability to drink milk
as an adult is a helpful
mutation.
 
Types of Mutations
Gene Mutations
 
Change in the 
nucleotide sequence 
of a
gene
May only involve a 
single nucleotide
 
Types of Gene Mutations
 
Point Mutations
a.
Missense
b.
Nonsense
c.
Silent
Frameshift
a.
Insertions
b.
Deletions
 
Point Mutations
 
point mutation
 or 
substitution
 is a
genetic mutation where a 
single nucleotide
base is changed.
a. Missense Mutation
This type of mutation is a 
change in one DNA base pair
that results in the substitution of 
one amino acid for
another 
in the protein made by a gene. Example is 
Sickle
cell anemia
 
b. Nonsense Mutation
 
A nonsense mutation is 
also a change in one
DNA base pair
. Instead of substituting one
amino acid for another, however, the altered
DNA sequence prematurely signals the cell
to stop building a protein. This type of
mutation results in a shortened protein that
may function improperly or not at all.
Examples include 
Duchenne Muscular
Dystrophy
 and 
Thalassemia
 
 
Normal condition
DNA
5’ATG 
 
ACT 
 
CAC 
 
CGA 
 
GCG 
 
CGA 
 
AGC 
 
TGA3’
3’
TAC 
 
TGA 
 
GTG 
 
GCT 
 
CGC 
 
GCT 
 
TCG 
 
ACT5’
mRNA
AUG   ACU 
 
CAC 
 
CGA 
 
GCG 
 
CGA 
 
AGC 
 
UGA
Protein
Met
     
Thr
         
His
       
Arg
      
Ala
       
Arg
       
Ser
      Stop
 
Nonsense mutation
DNA
5’ATG 
 
ACT 
 
CAC 
 
T
GA 
 
GCG 
 
CGA 
 
AGC 
 
TGA3’
3’
TAC 
 
TGA 
 
GTG 
 
A
CT 
 
CGC 
 
GCT 
 
TCG 
 
ACT5’
mRNA
AUG   ACU 
 
CAC 
 
U
GA 
 
GCG 
 
CGA 
 
AGC 
 
UGA
Protein
Met
     
Thr
         
His
       
Stop
 
c. Silent Mutations
 
Silent mutations
 are mutations in DNA that
do not have an observable effect on the
organism's phenotype.
 
For example, if the codon 
AAA
 is altered to
become 
AAG
, the same amino acid – 
lysine
 –
will be incorporated into the 
peptide
 chain
 
Frame Shift Mutations
 
1. Insertion Mutations
An insertion changes the number of DNA bases in
a gene by adding a piece of DNA. As a result, the
protein made by the gene may not function
properly.
Example
 
UUU
 
UUA
 
UCU
  
Phe-Leu-Ser
UUU
 
UUA
 
UUU
 
UCU
 
Phe-Leu-
Phe-
Ser
 
2. Deletion
 
A deletion changes the number of DNA bases
by removing a piece of DNA. Small deletions
may remove one or a few base pairs within a
gene, while larger deletions can remove an
entire gene or several neighboring genes. The
deleted DNA may alter the function of the
resulting protein(s).
UUU UUA 
UUU 
UCU
  
Phe-Leu-
Phe-
Ser
UUU UUA UCU
   
Phe-Leu-Ser
 
 
Types of Mutations
 
2.
  
Chromosomal
 mutation – may affect
 
more than one gene
  
Examples: nondisjunction, translocation
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A mutation in biology refers to changes in the nucleotide sequence of an organism's genome. These alterations can either be harmful, leading to conditions like cancer, or beneficial, such as providing antibiotic resistance. Mutations can occur in somatic cells or gametes, affecting both the individual and potentially their offspring. Understanding different types of mutations like gene mutations and point mutations is crucial in comprehending the intricacies of genetics and evolutionary processes.


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  1. MUTATIONS

  2. In biology, a mutation is an alteration of the nucleotide sequence of the genome of an organism May occur in somatic cells (aren t passed to offspring) May occur in gametes (eggs & sperm) and be passed to offspring

  3. Mutations can: - be bad, leading to cancer, aging, birth defects, self-aborted embryos

  4. CACGTGGACTGAGGACTCCTC Codon for CTC = glutamate CACGTGGACTGAGGACACCTC Codon for CAC = valine What does it matter???

  5. - be good, making an organism survive better in its environment - Example: bacteria becoming antibiotic-resistant The ability to drink milk as an adult is a helpful mutation.

  6. Types of Mutations

  7. Gene Mutations Change in the nucleotide sequence of a gene May only involve a single nucleotide

  8. Types of Gene Mutations Point Mutations a. Missense b. Nonsense c. Silent Frameshift a. Insertions b. Deletions

  9. Point Mutations A point mutation or substitution is a genetic mutation where a single nucleotide base is changed.

  10. a. Missense Mutation This type of mutation is a change in one DNA base pair that results in the substitution of one amino acid for another in the protein made by a gene. Example is Sickle cell anemia

  11. b. Nonsense Mutation A nonsense mutation is also a change in one DNA base pair. Instead of substituting one amino acid for another, however, the altered DNA sequence prematurely signals the cell to stop building a protein. This type of mutation results in a shortened protein that may function improperly or not at all. Examples include Duchenne Muscular Dystrophy and Thalassemia

  12. Normal condition DNA 5 ATG ACT 3 TAC TGA CAC GTG CGA GCT GCG CGC CGA GCT AGC TCG TGA3 ACT5 mRNA GCG AUG ACU CAC CGA CGA AGC UGA Protein Met Thr His Arg Ala Arg Ser Stop

  13. Nonsense mutation DNA 5 ATG ACT 3 TAC TGA CAC GTG TGA ACT GCG CGC CGA GCT AGC TCG TGA3 ACT5 mRNA UGA AUG ACU CAC GCG CGA AGC UGA Protein Met Thr His Stop

  14. c. Silent Mutations Silent mutations are mutations in DNA that do not have an observable effect on the organism's phenotype. For example, if the codon AAA is altered to become AAG, the same amino acid lysine will be incorporated into the peptide chain

  15. Frame Shift Mutations 1. Insertion Mutations An insertion changes the number of DNA bases in a gene by adding a piece of DNA. As a result, the protein made by the gene may not function properly. Example UUU UUA UCU UUU UUA UUU UCU Phe-Leu-Phe-Ser Phe-Leu-Ser

  16. 2. Deletion A deletion changes the number of DNA bases by removing a piece of DNA. Small deletions may remove one or a few base pairs within a gene, while larger deletions can remove an entire gene or several neighboring genes. The deleted DNA may alter the function of the resulting protein(s). UUU UUA UUU UCU UUU UUA UCU Phe-Leu-Phe-Ser Phe-Leu-Ser

  17. Types of Mutations 2. Chromosomal mutation may affect more than one gene Examples: nondisjunction, translocation

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