mutation history of mutation classification of mutation types of mutation syndrome due to mutation chromosomal variations in number causes of mutation to occur mutagen types

1. Mutation

2. PRESENTD BY:
M.SOHAIL RIAZ
PRESENTED TO:
DR. ANUM SAJID

3. Mutation
 A change of the nucleotide sequence of the
genome of an organism or Sudden change in
genetic material is known as mutation
 A mutation is a change that occurs in our DNA
sequence, either due to mistakes when the DNA is
copied or as the result of environmental factors such
as UV light and cigarette smoke
 A Mutation occurs when a DNA gene is damaged
or changed in such a way as to alter the genetic
message carried by that gene

4. CONT……..
Mutants:
 Individuals showing these changes are known as
mutants
Variant:
 An individual showing an altered phenotype due to
mutation are known as variant
Mutagens:
 Factor or agents causing mutation are known as
mutagens

5. CONT……
Gene mutation or Point mutation:
 Mutation which causes changes in base sequence of
a gene are known as gene mutation or point
mutation

6. History
 English farmer Seth Wright recorded case of
mutation first time in 1791 in male lamb with unusual
short legs.
 The term mutation is coined by Hugo de Vries in
1900 by his observation in Oenothera.
 H. J. Muller induced mutation in Drosophila by using
X- rays in 1927; he was awarded with Nobel prize in
1946.

7. Characteristics of Mutation
 Generally mutant alleles are recessive to their wild
type or normal alleles
 Most mutations have harmful effect, but some
mutations are beneficial
 Spontaneous mutations occurs at very low rate
 Some genes shows high rate of mutation such
genes are called as mutable gene

8. CONT…….
 Highly mutable sites within a gene are known as hot
spots
 Mutation cans occur in any tissue/cell of an
organism

9. Classification of
mutation

10. Based on the survival of an individual
Lethal mutation:
 When mutation causes death of all individuals
undergoing mutation are known as lethal
Sub lethal mutation:
 It causes death of 90% individuals
Sub vital mutation:
 Such mutation kills less than 90% individuals

11. CONT…
Vital mutation:
 When mutation don’t affect the survival of an
individual are known as vital
Super vital mutation:
 This kind of mutation enhances the survival of
individual

13. Based on tissue of origin
Somatic mutation
 A mutation occurring in somatic cell is called
somatic mutation.
 In asexually reproducing species somatic mutations
transmits from one progeny to the next progeny

14. CONT……
Germinal Mutation
 When mutation occur in gametic cells or
reproductive cells are known as germinal mutation
 In sexually reproductive species only germinal
mutation are transmitted to the next generation

16. Based on causes of mutation
Spontaneous mutation
 Spontaneous mutation occurs naturally without any
cause
 The rate of spontaneous mutation is very slow
 Rate of spontaneous mutation is higher in
eukaryotes than prokaryotes
 E.g UV light of sunlight causing mutation in bacteria

17. CONT……
Induced Mutation
 Mutations produced due to treatment with either a
chemical or physical agent are called induced
mutation
 The agents capable of inducing such mutations are
known as mutagen
 Use of induced mutation for crop improvement
program is known as mutation breeding
 E.g X- rays causing mutation in cereals

19. Based on direction of mutation
Forward mutation
 When mutation occurs from the normal/wild type
allele to mutant allele are known as forward
mutation
Reverse mutation
 When mutation occurs in reverse direction that is
from mutant allele to the normal/wild type allele are
known as reverse mutation

21. Type of trait affected
Visible mutation
 Those mutation which affects on phenotypic
character and can be detected by normal
observation are known as visible mutation
Biochemical mutation
 Mutation which affect the production of
biochemicals and which does not show any
phenotypic character are known as biochemical
mutation

22. Chromosome
Mutations

23. Five types exist:
 Deletion
 Inversion
 Translocation
 Non-disjunction
 Duplication
 Frameshift

24. DEF………
Deletion:
 Deletions are mutations in which a section of DNA is
lost, or deleted
Inversion:
 A DNA sequence of nucleotides is reversed
 Inversions can occur among a few bases within a
gene or among longer DNA sequences that contain
several genes

26. CONT…..
Translocation:
 Involves two chromosomes that aren’t homologous
 Part of one chromosome is transferred to another
chromosomes
Non-disjunction:
 Failure of chromosomes to separate during meiosis
 It Causes gamete to have too many or too few
chromosomes.
 Disorders: – Down Syndrome – three 21st chromosomes
– Turner Syndrome – single X chromosome –
Klinefelter’s Syndrome –

28. CONT….
Duplication:
 It occurs when a gene sequence is repeated
Frameshift:
 It include Inserting or deleting one or more
nucleotides
 This is like changes the “reading frame” like
changing a sentence
 Proteins built incorrectly in this

30. Chromosomal
Variation in
Number

31. 1.Aneuploidy
 The abnormal condition where one or more
chromosomes of a normal set of chromosomes are
missing or present in more than their usual number
of copies
2.Nullisomy
 It includes the loss of both pairs of homologous
chromosomes
3.Monosomy
 It includes the loss of a single chromosome

34. CONT………
4.Trisomy
 It includes the gain of an extra copy of a
chromosome
5.Tetrasomic
 It includes the gain of an extra pair of homologous
chromosome

36. Causes of
Mutations To
Occur

37. DNA fails to copy accurately:
 When a cell divides, it makes a copy of its DNA and
sometimes the copy is not quite perfect
External Influences/Mutagens:
 In genetics, a mutagen is a physical or chemical
that changes the genetic material, usually DNA, of
organism and thus increases the frequency of
mutations above the natural background level

38. CONT……
Effects of mutagens:
 It can affect the replication of the DNA
 It also can lead to cell death
 It produces mutations that can result in aberrant,
loss of function for a particular gene
 So due to the accumulation of mutations may lead
to cancer

39. CONT……
 Chromosomal breakages and rearrangement of the
chromosomes such as translocation, deletion, and
inversion
 Some mutagens can cause aneuploidy and change
the number of chromosomes in the cell

40. Types of
Mutagens

41. Biological Agents
1.Virus
 Virus DNA may be inserted into the genome and
disrupts genetic function
 Infectious agents have been suggested to cause
cancer
2.Bacteria
 Some bacteria such as Helicobacter pylori cause
inflammation during which oxidative species are
produced, causing DNA damage and reducing
efficiency of DNA repair systems, thereby increasing
mutation

42. Physical mutagens
 It consist of Ionizing radiations such as X-rays,
gamma rays and alpha particles
 They may cause DNA breakage and other damages
 The most common sources include cobalt-60 and
cesium-137
 Ultraviolet radiations with wavelength above 260 nm
–are absorbed strongly by bases, producing
pyrimidine dimers, which can cause error in
replication if left uncorrected

43. CONT……
 A large number of chemicals may interact directly
with DNA
 However, many are not necessarily mutagenic by
themselves, but through metabolic processes in cells
they produce mutagenic compounds

44. Mutation in Human
 Down Syndrome
 Edward’s syndrome
 Patau syndrome
 Monosomy 7
 Tetrasomy 18p
 Pallister–Killian syndrome

45. Down Syndrome:
 It is also known as trisomy 21, is a genetic disorder
caused by the presence of all or part of a third copy
of chromosome 21
 It is typically associated with physical growth delays,
characteristic facial features and mild to moderate
intellectual disability
 The average IQ of a young adult with Down
syndrome is 50, equivalent to the mental age of an
8 or 9 year old child, but this varies widely

47. Edward’s syndrome:
 It is a chromosomal disorder caused by the
presence of all or part of an extra 18th chromosome
 This genetic condition almost always results from
nondisjunction during meiosis
 It is named after John Hilton Edwards, who first
described the syndrome in 1960
 It is the second most common autosomal trisomy,
after Down syndrome, that carries to term
 Many parts of the body are affected. Babies are
often born small and have heart defects

49. Patau syndrome:
 It is a syndrome caused by a chromosomal
abnormality, in which some or all of the cells of the
body contain extra genetic material from
chromosome 13
 The extra genetic material from chromosome 13
disrupts the normal course of development, causing
multiple and complex organ defects

51. Monosomy 7:
 It is typically characterized by early childhood onset
of evidence of bone marrow insufficiency/failure
associated with increased risk for myelodysplastic
syndrome (MDS) or acute myelogenous leukemia
(AML)
 Bone marrow failure/MDS/AML follows within a few
months to years of identification of a monosomy 7
cell line in peripheral blood
 Nearly all individuals reported with familial mosaic
monosomy 7 have died of their disease

52. Myelodysplastic syndromes (MDS)
 Myelodysplastic syndromes (MDS) are a group of
cancers in which immature blood cells in the bone
marrow do not mature, so do not become healthy
blood cells
 Early on, no symptoms typically are seen
 Later, symptoms may include feeling tired, shortness
of breath, easy bleeding, or frequent infections

53. Acute myelogenous leukemia (AML)
 Acute myelogenous leukemia (AML) is a cancer of
the blood and bone marrow
Symptoms
 Fever, Bone pain, fatigue, Shortness of breath, Pale
skin, Frequent infections, Easy bruising, Unusual
bleeding, such as frequent nosebleeds

55. Tetrasomy 18p:
 It is a genetic condition that is caused by the
presence of an isochromosome, composed of two
copies of the short arm of chromosome 18
 It is characterized by multiple medical and
developmental concerns
 Feeding difficulties, respiratory difficulty and
jaundice are also relatively frequent in it

56. Isochromosome
 An isochromosome is an unbalanced structural
abnormality in which the arms of the chromosome
are mirror images of each other

58. Pallister–Killian syndrome:
 Pallister–Killian syndrome (also tetrasomy 12p
mosaicism or Pallister mosaic aneuploidy syndrome)
is an extremely rare genetic disorder occurring in
humans
 Pallister-Killian occurs due to the presence of the
anomalous extra isochromosome 12p, the short arm
of the twelfth chromosome
 Distinctive facial features, sparse hair, areas of
unusual skin coloring (pigmentation), and other
birth defects