Detail description of each aspects of mutation with examples

2. WHAT IS MUTATION ?
 Mutations are the changes in the genetic material , therefore
change in the Gene segment .
 In a gene mutations, the DNA code will have a base missing ,
added or exchanged in the codon .
 Mutation is a need for evolution because it is not always
harmful .
 Causes of mutation :-
Spontaneous – DNA goes chemical change , Replcation error
Induced – Mutagens,carcinogen,Radiation,chemicals etc.
 Mutation can be of two types :-
 Chromosomal mutation
 Gene mutation

5. CHROMOSOMAL MUTATION

6. GENE MUTATION
 It is the change in the particular segment of the
gene which leads to the change of the sequence .
 Gene mutations on the basis of occurence:-
i. Hereditary mutations are inherited from a parent and are present
throughout a person’s life in virtually every cell in the body
ii. Acquired (or somatic) mutations occur at some time during a
person’s life and are present only in certain cells, not in every cell
in the body
 Gene mutation is of two types :-
i. Point mutation
ii. Frameshift mutation

7. POINT MUTATION
 One or more bases are inserted into the orignal DNA base sequence
 This is sometime called as frameshift mutation because it shifts the
codon reading frame
 Substitution mutation comes under point mutation and the most
common example of it is sickle cell anemia .

8. SUSTITUTION MUTATION
Sickle cell anemia is the result of a point mutation, a change in just one
nucleotide in the gene for hemoglobin i.e Glutamine is changed to Valine.
This mutation causes the hemoglobin in red blood cells to distort to a sickle
shape when deoxygenated. The sickle-shaped blood cells clog in the
capillaries, cutting off circulation

9. INSERTION
 An insertion changes the number of DNA bases in a
gene by adding a base to DNA. As a result, the protein
made by the gene may not function properly.

10. DELETION
 A deletion changes the number of DNA bases by
removing a base of DNA. Small deletions may remove
one or a few base pairs within a gene,

11. Single Nucleotide Polymorphism
 Each SNP represents a
difference in a
single DNA building block,
called a nucleotide.
 Most commonly, these
variations are found in
the DNA between genes.
 List of SNPs causing genes
can be found in SNP
database developed by
NCBI

12. SYNONYMOUS MUTATION
 Synonymous mutations are point mutations, they are just a miscopied DNA
nucleotide that only changes one base pair in the RNA copy of the DNA.
 A codon in RNA is a set of three nucleotides that encode a specific amino
acid. Most amino acids have several RNA codons that translate into that
particular amino acid.
 Most of the time, if the third nucleotide is the one with the mutation, it will
result in coding for the same amino acid. This is called a synonymous
mutation
 Synonymous mutations do not change anything and no changes are made.
That means they have no real role in the evolution of species since the gene
or protein is not changed in any way. Like - GAT or GAC both codes for
aspartic acid ; GAA or GAG both code for Glutamic acid .

13. SILENT MUTATION
 Silent mutations are base substitutions that result in no
change of the amino acid or amino acid functionality
when the altered messenger RNA (mRNA) is translated.

14. NON –SYNONYMOUS MUTATION
 Non-synonymous mutations have a much greater effect on an individual
than a synonymous mutation. In a non-synonymous mutation, there is
usually an insertion or deletion of a single nucleotide in the sequence during
transcription when the messenger RNA is copying the DNA.
 This single missing or added nucleotide causes a frameshift mutation which
throws off the entire reading frame of the amino acid sequence and mixes
up the codons. This usually affect the amino acids that are coded for and
change the resulting protein that is expressed.
 The severity of this kind of mutation depends on how early in the amino
acid sequence it happens. If it happens near the beginning and the entire
protein is changed, this could become a lethal mutation.
 Another way a non-synonymous mutation can occur is if the point mutation
changes the single nucleotide into a codon that does not translate into the
same amino acid . Like – GGA (glycine) to AGA (arginine) ; CAA
(Glutamine) to CAC (Histidine) .

15. MIS SENSE 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.

16. NON SENSE MUTATION
 A non sense codon is the substitution of a stop codon
for original codon .
 It causes the termination of the Protein synthesis
 If it is near at the start causes whole loss of the gene
segment

18. FRAMESHIFT MUTATION
 Inserting or deleting one or more nucleotide
 Which changes the reading frame which leads to the formation
of the incorrect protein.
 INSERTION of the new base in the DNA sequence and
DELETION of the base in the DNA sequence leads to the shift
in the frame .
 A frameshift mutation is not same as the single nucleotide
polymorphism ,in which single nucleotide is replaced rather
than insertion or deletion .

20. INSERTION
 An insertion changes the number of DNA bases in a gene
by adding a piece of DNA. As a result, the whole
sequence changes and the protein made by the gene may
not function properly.

21. Before After
Tay sachs disease effect in brain corpus
callosum

22. DELETION
 A deletion changes the number of DNA bases by removing
a piece of DNA which results in removal of an entire gene
or several neighboring genes. The deleted DNA alter the
function of the resulting protein .
 Eg- cystic fibrosis

23. cystic fibrosis

24. STOP LOSS STOP GAIN
 A stop-loss mutation is the
loss of the
normal stop codon
by mutation to encode an
amino acid.
 This will result in the
extension of the carboxyl
terminus of the protein
until the next stop codon
is encountered
 Which cause a elongated
protein formation
 A stop-Gain mutation is
the gain of the
normal stop codon
by mutation .
 This will result in the
termination of the protein
chain early .
 Which cause a no protein
formation

25. GENETIC DISORDER
 Disorders are caused by changes to the genes and
chromosomes that result in the protein not being
expressed or the protein expressed not functioning
correctly . Examples :-
 Duchenne muscular dystrophy

26. Duchenne muscular dystrophy

27. • Huntington’s disease