Mutations are sudden changes in the genetic material of an organism that can be caused by mutagens like chemicals, radiation, or errors in DNA replication. There are two main types of mutations: gene mutations, which alter the DNA sequence of a gene, and chromosomal mutations, which involve changes to chromosomes like deletions, duplications, inversions, and translocations of DNA segments. Gene mutations can be point mutations, which substitute a single nucleotide, or frameshift mutations, which insert or delete nucleotides and alter the reading frame. Chromosomal mutations can cause diseases like Down syndrome, which results from trisomy of chromosome 21.
2. Mutation is a sudden change in
physical and chemical properties
of gene/genetic material of an
organism.
Mutation result in a DNA base
pair change or chromosome
change.
3. Substances which causes mutations are known as mutagens
MUTAGENS
CHEMICAL
BASE
ANALOGUES
Eg. 5 Bromo
uracil
BASE
MODIFYING
AGENTS
Eg. Alkytaing
agents,
hydroxylating
agents
INTERCALATING
AGENTS
Eg. Acridine,
RADIATION/
PHYSICAL
IONISING
X rays
α rays
Β rays
NON-IONISING
Uv rays
6. Morphological mutations
DELETION
• It involves loss of segment of a chromosome.
Deletion starts by breaks occurring in chromosomes
• The detached fragment of dna does not reattach to the
original chromosome.
• Consequences of deletion depends on the genes/parts of
genes that has been lost.
• Detectable phenotypic changes occurs when a whole
part/ or an entire chromosome is lost.
7. Eg. Cri du chat syndrome
• Occurs due to deletion of lower
short arm of chromosome #5
• Clinical manifestations:
moon shaped face, cry with a
sound like new of a cat,
mental retardation and a
number of physical
abnormalities.
8. DUPLICATION
• It involves in the doubling of a segment of a
chromosome
• May or may not be lethal to organisms.
• Segment of dna breaks off and attaches into homologous
chromosome.
• Duplication arises from unequal crossing over occurs
between misaligned/ inaccurately paired homologous
chromosomes.
9. Eg. Chromosome 1q21.1 duplication syndrome
Clinical manifestations :
large head size, autistic behavior, heart
problems, mental retardation.
10. INVERSION
• Occurs when a chromosome is excised and then
reintegrated in an orientation 180˚ from the original
orientation.
• When the inverted segment includes the centromere, the
inversion is called pericentric inversion
• When the inverted segment occurs on one chromosome
arm and does not include the centromere, the inversion is
called paracentric inversion
11. Eg. Chromosome 9 inversion
Clinical manifestations: congenital
abnormalities, growth retardation,
infertility in males, pregnancy loss
12. TRANSLOCATION
• A translocation is a chromosome mutation in which there is a
change in position of chromosome segments and gene sequences they
contain .
• Intrachromosomal translocation involves a change in position of
chromosome segment within the same chromosome.
• Interchromosomal translocation involves the transfer of a
chromosome segment from one chromosome into a non-homologous
chromosome.
• If the interchromosomal translocation occurs in one way,
it is known as non reciprocal translocation, and if
it involves exchange of segments between 2 chromosome, its is
reciprocal translocation
13. Eg. Chronic myeloginous
leukemia
• Due to mutation in leukemic cells called
Philadelphia chromosome, which results from
reciprocal translocation of part of long arm of
chromosome no. 22 and a small part of tip of
chromosome no. 9. this results in activation
of oncogenes (c-myc)
14.
15. Numeric mutation
EUPLOIDY
• Mutations which results in changes in
complete sets of chromosomes.
• Monoploidy and polyploidy are lethal for
animals but are tolerated by plants.
• They have played a significant role in plant
speciation.
• In humans, most common polyploidy is
triploidy. Triploidy is always lethal and seen in
15-20% of spontaneous abortions. About 1 in
10,000 live births is triploid, but most die
within one month.
• Triploid infants have many abnormalities,
including characteristic large head
16. ANEUPLOIDY (±1/±2)
• One to a few whole chromosomes are lost from or
added to the normal set of chromosomes.
• Aneuploidy occurs mainly due to non-disjunction of
chromosomes during meiosis.
• Non-disjuntion is the irregular distribution to the cell
poles of sister chromatids in mitosis or of homologous
chromosome in meiosis.
• In non-disjunction , one progeny nucleus with more
than and one with less than the normal no. of
chromosomes are produced.
• Unpaired chromosomes may be lost during anaphase
and not included in one of the daughter nucleus.
17. NULLISOMY
• A loss of one homologous chromosome
pair results in a nullisomic cell.
• The nullisomic cell is 2n-2.
18. MONOSOMY
• A loss of a single chromosome results in
monosomic cell.
• The monosomic cell is 2n-1
• Autosomal monosomy in human is only found
rarely in spontaneous abortions and live births.
• Monosomic embryos do not develop significantly
and are lost during pregnancy
19. Eg. Turner syndrome
• Monosomy in sex chromosomes
chromosome no. 45
• Individuals have an x but no y
chromosome. (XO individuals) and
have normal sets of autosomes in
females.
Clinical manifestations:
sterile, shorter than average, poor secondary sexual
characteristics, web like necks, poorly developed
breasts.
Monosomic will produce 2 kinds of gametes n and n-1
20. TRISOMY
• A trisomic cell contains a single extra
chromosome so the cell
• has 3 copies of one chromosome type and 2
copies of every other chromosome type.
• A trisomic cell is 2n+1
trisomy of #8,#13,#18 do not survive long
• Only one in trisomy #21 does survival to adulthood
occur
21. Eg. Trisomy of chromosome no.21 (down syndrome)
• Presence of 3 copies of chromosome #21
Clinical manifestation:
Low IQ, epicanthel folds over the eyes, short and broad
hands, sterility, shorter life span, below average height.
22.
23. TETRASOMY
• A tetrasomic cell contains an extra
chromosome pair, resulting in the presence of 4
copies of one chromosome type and 2 copies of
every other chromosome type.
• A tetrasomic cell is 2n+2
24. Eg. Klinefelters syndrome
Phenotypic features:
underdeveloped testes, taller than average males, lower than
average IQ, breast development in about 50% of individuals.
25. GENE MUTATIONS
• A mutation in a gene sequences is called
gene mutation.
• It can involve any one of a number of
alteration of DNA sequences of the gene,
including base-pair substitutions and addition
/deletions of one or more base-pair.
• Those gene mutations which affects a singe
base-pairs of DNA are called point mutations.
27. POINT MUTATIONS
It is a specific type of base- pair
substitution mutation involving a change
from one base pair change to another.
28. Eg. Sickle cell anemia
• at 6th position glutamic acid is replaced by valine
in hemoglobin B chain
• “sickle” shape to RBC
• Most common in African-Americans
• Pain associated with blocked vessels, causes
anemia (fatigue)
• Common where mosquito-borne malaria is
present
30. SILENT
It is a base pair change that alters a
codon in the mrna such that the same
amino acid is inserted in the protein.
It has no effect on the function of
protein.
31.
32. MIS SENSE
It is a base pair change in dna causes a change in
mRNA codon so that a different amino acid is inserted
into polypeptidein place of the one specified by the
wild type
MISSENSE
Conservative
Misense
mutation
Non
conservative
missense
mutation
33.
34. CONSERVATIVE MISSENSE MUTATION
It is a base pair change in gene that changes a codon in
the mRNA such that the resulting amino acid is
chemically equivalent to the original and does not affect
proteins function.
35. NON CONSERVATIVE MISSENSE MUTATION
it is a base pair change in a gene that changes a
codon in the mRNA such that resulting amino acid
is different from the original. It can alter the
function of the protein.
36. NON SENSE
It is a base pair change in DNA that results in
the change of an mRNA codon from one that
specifies an amino acid to a chain terminating
(nonsense) codon (UGA, UAA, UGA). This gives
rise to incomplete or premature polypeptide
fragments (non functional ) from the
ribososmes.
38. FRAMESHIFT MUTATION
• This mutation results from the addition or
deletion of one or more base pairs of gene. An
addition/ deletion shifts the frame of reading of mRNA
by one base so that incorrect amino acid are added to
the polypeptide chain after mutation site.
• This results in a non functional polypeptide.
• Nonfunctionally is mainly due to the large scale
changes to polypeptide chain and chemical
composition of DNA. This can results in disruption of
biochemical process of cell.
• Silent mutations can lead premature translation of
mRNA due to extended polypeptide.
39.
40. • Recessive disorder
• Mutation stops production of protein in lung
cells, pancreas
• Thick mucus, bacterial infections in lung
“sweat test”
• Most common in Caucasians (1 in 3300)
• Chest percussions, diet supplements
Shortened life expectancy
Eg. Cystic fibrosis
