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• Mutation is basically alteration of one or more
nucleotides in an organism extra
chromosomal DNA, virus or any material
related to gene.
• Mutations occur due to mutagens.
• Permanent change.
• Vary in size from genome to genome.
• Alteration may be single or large fragment
containing one or more than one gene mutation
is cause of dissimilarities between individuals of
same species and different .
• It may lead to evolution.
• Mutations idea extends from Darwin to modern
• Since than there have been a lot of changes in
the definition of the term
• Today Mutations are important in order to
differentiate between the individuals.
• Prof Sir Mike Stratton :
• He was the first one who gave remarks on the
mutations that occur in embryo.
• Mutations can help in better understanding of
• DNA fails to copy accurately:
Most mutation is naturally occurring .when cell
devide it makes makes copy of DNA Some time
copy not perfect. Small difference from original
DNA is mutation.
• External influences can create mutations
Mutation can cause by specific chemicals or
radiations. These cause to break DNA. When cell
repair the DNA then it might not be a perfect
There are two types of mutations:
• Gene Mutation
• Chromosomal Mutation
• Point Mutation:
• Gene mutation is describe as any change in the
• This change occur in single nucleotide base or
• Due to this genetic variations occur.
• Some variations may help for better survive.
• Different mutagens which produce mutation.
• There are basic types
1. Point mutation
• Simple type of gene mutation.
• Single base pair altered.
• Mostly occur during DNA replication.
• Caused by mutagens.
• One or more nucleotide base pair are added into
a sequence of DNA.
• In which segment of DNA is removed which
consist of one or more nucleotide.
• Point mutation on basis of protein structure:
1. Silent Mutation.
2. Missense Mutation.
3. Nonsense Mutation.
• Frameshift mutation- Adding or deleting
nucleotides to a DNA sequence.
• A frameshift mutation is much worse than a point
mutation because it causes the entire DNA
sequence to be shifted over.
Example: DNA: ATTAAACCG
The absence of a vital enzyme called
Hexosamindase A (Hex-A)
Accumulation of GM2 in nerve
cells of the brain
However, in Tay-Sachs, there is no Hex-A so this
process does not occur
• Chromosome 15
showing location of
• Inherited monogenic disorder presenting as a
• Typically presents in childhood
▫ 7% of CF patients diagnosed as adults
• Most common life limiting recessive trait among
• Prognosis improving
▫ 38% of CF patients are older than 18
▫ 13% of CF patients are older than 30
• Median survival:
▫ Males: 32 years
▫ Females: 29 years
Genetics of CF
• Autosomal recessive.
• Gene located on chromosome 7.
Genetics of CF
• Most common mutation occurs in 70% of CF
chromosomes 3 base pair deletion leading to
absence of phenylalanine at position 508 (DF508)
of the CF transmembrane conductance regulator
• DF508 mutation leads to improper processing
and intracellular degradation of the CFTR
• Deletion is the lost of the nucleotides from the
chromosomes the loss could be in larger number
or in smaller number.
• Deletion is actually when a base is deleted from
• Chromosomal fragment are lost due to deletion
of a base.
• There is no specific location for deletion, it can
happens anywhere or everywhere.
• Sometimes the one copy of gene is lost from the
organism which have two copies before or
sometimes both the copies from an organism
• Duplication is opposite to deletion.
• A part is copied or replicated.
• A sequence is repeated or may be a single base
or two bases are repeated or duplicated.
• This type of chromosome have an extra
information or repeated information.
Mechanism of Duplication
• There are following five mechanism of
duplication that are defined below
• Duplication due to unequal crossing over occurs
during meiosis in misaligned homologous
• It occurs due to the replication of two elements
• It is actually a error in the DNA due to which short
sequences are repeated in the chromosomes.
• DNA polymerases starts copiyng the DNA during
• It place the Strand in wrong location and accidently
copy the strand again due to which the duplication
• Replication slippage is actually the repetitive
• Retrotransposons are genetic elements that
can amplify themselves in a genome.
• These DNA sequences use a "copy-and-paste"
mechanism, whereby they are
first transcribed into RNA, then converted back
into identical DNA sequences using reverse
transcription, and these sequences are then
inserted into the genome at target sites.
• Poliploid cells and organisms are those
containing more than two paired (homologous)
sets of chromosomes.
• Most species whose cells have nuclei
(Eukaryotes) are diploid, meaning they have two
sets of chromosomes—one set inherited from
• Aneuploidy is the presence of an abnormal
number of chromosomes in a cell, for example a
human cell having 45 or 47 chromosomes
instead of the usual 46.
• It does not include a difference of one or more
complete sets of chromosome.
• An inversion is a chromosome rearrangement in
which a segment of a chromosome is reversed end to
• Breakage and rearrangement within a chromosome.
• Inversions do not change the overall amount of the
• Show no particular abnormalities at the phenotypic
• Inversions usually do not cause any
• In individuals which are heterozygous for an
inversion, there is an increased production of
• This leads to lowered fertility due to production
of unbalanced gametes
There are two types of Inversion mutation in
• Pericentric Inversions.
• Paracentric Inversions.
• Pericentric inversions include the centromere
and there is a break point in each arm.
• Chromosome can be elongated or shorted after
the inversions have taken place.
• Paracentric inversions do not include
the centromere and both breaks occur in one
arm of the chromosome.
• A reversal of the normal order of genes in a
chromosome segment involving only the part of
a chromosome at one side of the centromere.
• Cytogenetic techniques may be able to detect
inversions, or inversions may be inferred
from genetic analysis.
In most species small inversions go undetected.
• The most common inversion seen in humans is
on chromosome 9, at inv(9)(p12q13).
• No harmful effects.
• Suspicion it could lead to an increased risk for
miscarriage or infertility for some affected
• A chromosome translocation is
a chromosome abnormality caused by
rearrangement of parts between
• Translocations can
be balanced or unbalanced.
in an even exchange of material with no genetic
information extra or missing, and ideally full
Where the exchange of chromosome material is
unequal resulting in extra or missing genes.
• Some human diseases caused by translocations are:
• Cancer: Described mainly in leukemia. Translocations
have also been described in solid malignancies such
as Ewing's sarcoma.
• Infertility: If parent is a carrier of balanced then chances
of an offspring being infertile are increased.
• Down syndrome: Caused by Translocation between
chromosome 21 and chromosome 14
• In which organism fitness is decreased and
produced a diseases.
• Sickle cell anemia, color blindness etc
Are all mutations harmful?
• Change the codes for protein synthesis.
• Single mutation or more than 10 mutation.
• Also called silent point mutation.
• Eye color.
• Wilms Tumor.
• Most inherited genetic diseases are recessive.
• Some disease caused by one copy of defective
• Rare (Huntington’s Disease)
• 5-10 deadly mutation in our body
(UV Radiation, X-rays)
Also called mutagens.
(Benzoyl peroxide, cigarette smoke)
iii. Infectious Agents.
• 28 April, 1986
• Chernobyl Disaster
• 985,000 excess cancers occurred between 1986
and 2004. (Russian Publication)
• 1.4 million excess cancers occurred
(2001, European Committee on Radiation Risk)
Sickle cell Anemia:
• Hemoglobin-Beta gene found on chromosome
• Sickle shaped red blood cells.
• Type of point mutation.
• Two copies of the mutated genes cause sickle cell
• Mutation in chromosome number 4.(HD
• Basal ganglia cells are destroyed.
• 50% chance.
• Symptoms appear between 30 to 50 ages.
• Mutation in p53, BRCA1, BRCA2
• BRCA1 = breast cancer 1
• BRCA2 = Breast cancer 2
• Which are helpful for humans.
i. Apolipoprotein AL Milano
ii. Increased bone density
iii. Malaria resistance
iv. Tetrachromatic vision
• All humans have a gene which are said to be
• The function of this gene is to transport
cholesterol via the process of bloodstream.
• It is considered more beneficially due to the
removal of cholestrol from arteries.
Increased bone density:
• The gene which caused bone density in human
being are said to be low lipoprotein related to
protein 5 (LRP5).
• These variations occur in humans due to the
hemoglobin variation that make it like sickle
• The missing of one copy of that gene in human
causes 29% chances to get malaria. On the other
hand people with two copies of this gene
respond to 93% of that disease
Tetra chromatic vision:
• Different genes present in humans shows
different color vision of light.
• The gene which has one kind of cone show blue
color at chromosome at 7.
Beneficial mutation in organisms:
1. Nylonase: nylon bacteria
• Nylonase are the most authentic example of
beneficial mutation in bacteria.
• Nylonase eat the short molecule of nylon 6.
Gene mutation: Almond Trees:
• The species which have almond contain
• Amygdalin is a chemical that convert the cyanide
into human body.