Download CHROMOSAL MUTATIONS SUBSTITUTION

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CHROMOSAL MUTATIONS
SUBSTITUTION
DELETION
Results in
1. SILENT MUTATIONS
2. MISSENSE MUTATIONS
3. NONSENSE MUTATIONS
INSERTION
Results in
1. TRANSLOCATION
2. INVERSION
l. FRAMESHIFT MOTIONS
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MUTATIONS
• Mutations are errors/chan ges made in the DNA sequence that are
inherited.
• Mutations may have deleterious side effects, no effect or positive
effects for an organism.
• Some mutations in the genome lead to the developme nt of diseases
that may be inherited.
Example: Cystic Fibrosis disease is an example of Negative
(deleteriou s) Side Effect. Mutations in the Cystic Fibrosis
Transmem brane Regulator (CFTR) gene that res~lt in
Cystic Fibrosis can be passed on from parent to child. This
is a negative side effect.
• The large size of the human brain is the res.\It series of Positive
Side Effect of Mutations.
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POINT MUTATIONS:
• Point Mutations are the Mutations at a specific base pair in the
genome.
• Also known as Gene Mutations.
TYPES OF POINT MUTATIONS
. ~· SILENT MUTATIONS
. 2.'MISSENSE MUTATIONS
3. NONSENSE MUTATIONS
}
caused by SUBSTITUTION
of a Base Pair
4. FRAMESHIFT MUTATIONS} caused by Deletion or Insertion
WHAT IS SUBSTITUTION?
• The replacement of one ~ase in a DNA sequence by another base
is known as substitution.
Examples: silent Mutations, Missense Mutations and Nonsense
Mutations.
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SILEN T MUTA TIONS :
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• A mutati on that does not result in a ·change in the amino acid
coded for ~nd, therefo re, does not cause any phenot ypic change.
• Silent mutati ons may occur due to the redund ant nature of
geneti c code.
Examp le:
stop
Base-Pai r Substitut ion
no effect on amino acid sequence
• For examp le: ACA and ACU both code for Threon ine.
a.- : ACA : Threon ine
The codon for Threo nine is
If the third base 'A' is Substi tuted
.,..: ACU : Still it is Threon ine.
with 'U', it becom es
This is an examp le silent mutati on becaus e the base pair
Substi tution is coded for t~e same amino acid, Threon ine.
• Sile11t mutati ons may occur in the noncod ing regions (Intron s) of
DNA. If these areas are excised out of the m.RNA primar y
transc ript during the proces s of transc ription , the mutati on never
surfac es.
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MISSENCE MUTATIONS:
• A mutation that results in the single substitution of one amino
acid in the resulting polypeptide.
• In other words, a base in codon is substituted by another base that
results in a different amino acid in polypeptide chain.
• Example: Sickle cell Anemia
The code for Threonine is
: f~ C
A
: Threonine
H the first base of the collon "A" is
J,
substituted with "C", it becomes
\ C.J C A :Proline
NONSENSE MUTATIONS:
• Nonsense mutation is a mutation that converts a codon 'ror an
Amino Acid into a termination (stop) codon.
• · During translation, only the part of the protein that precedes the
stop codon is produced, and the fragment may be digested by the
proteases.
' Nonsense mutations are often lethal to the cell.
..
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FRAMESHIF T MUTATIONS :.
• A mutation that causes the reading frame of codons to change,
usually resulting in different ·amino acids being incorporated into
polypeptide..
• Frameshift mutations are caused by Deletion or Insertion of one
or more nucleotide bases.
WHAT IS DELETION?
• The elimination of a base pair or group of base pairs from a DNA
sequence is known as Deletio~. This results in different amino
acid sequence in the protein.
. . ·::
5'
3'
• As a result of deletion, the protein structure will be altered
drastically and inevitably r.esults in a defective protein. This type
of shifts in the Reading Frame usually results in drastic errors.