Mendels original paper

1. MENDELIAN INHERITANCE AND
IMPLICATION IN PLANT BREEDING
Presentation by:
Arushi Arora
(A-2016-30-050)
M.Sc. 2nd Year
Dept. of Crop Improvement

2. Topics to be covered
Mendel’s history
Mendel’s original paper
Laws of Inheritance
Deviations of Mendelian Inheritance
Implications in Genetics and Plant Breeding
2

3. THE MENDELIAN TIMELINE
3

4. Mendel’s life
• Born on July 22, 1822 as a II child to Anton &
Rosine , was named Johann.
• I and III child were daughters, Veronika & Theresia
respectively.
 Worked with his father in the orchard.
4

5. • Joined Heinzendorf School, studied natural history,
natural science with elementary education.
• Learned essentials of fruit growing & beekeeping.
• Best student marked superexcellent in almost all
branches.
5

6. • Suffered serious illness & stresses during 1838 &
forced to go home.
• Parents not in position to support financially, father
had a serious accident.
• Fell sick again & compelled to spend a year at home.
6

7. Mendel’s resume
7

8. YEAR LANDMARKS
July 22,1822 Born in the Austrian Empire .
1841 Attended the Philosophical Institute of the
University of Olmutz.
1843 Joined the St. Thomas Monastery.
1850 Failed the oral portion of his teaching exam.
1851-1853 University of Vienna: Mendel studied physics,
mathematics and natural history.
1853 Returned to the Abbey ,where he becomes the
teacher he has wanted to be. He primarily
teaches physics.
8

9. YEAR LANDMARKS
1854 Started his famous experiments in the Abbey garden, He
spent two years selecting Pisum lines with constant
characteristics.
1856-63 Cultivated and tested pea plants.
1865 Lectured on “Experiments in Plant Hybridization” at the
February 8 and March 8 meetings of the Natural Science
Society (Brno).
February 8,
1866
Published his paper in Annual proceedings of the society.
1869 Results on Hieraceum.
1867 Became abbot of the monastery and replaces his mentor,
Abbot C.F. Napp, as the abbot of the monastery.
January 6,
1884
Died due to chronic case of nephritis.
9

10. Mendel’s paper
 In (1865) -Mendel read his paper on “Experiments
in Plant Hybridization” to the Natural History
Society of Brunn.
 In 1866, Mendel work was published on heredity in
the Annual Proceedings of Natural History Society
of Brunn.
 Translated from German into English by William
Bateson.
10

11. MENDEL’S GENETICS IN HIS OWN
WORDS....
11

12. HIGHLIGHTS OF MENDEL’S PAPER
 Mendel quoted the
exhaustive work of
scientists working
prior to him.
12

13.  He used statistics in
his experimental work
which was the most
important key to
success.
13
New era of
statistical
genetics
begin

14.  He mentioned the main
reasons for selecting pea
plant.
14

15. Advantages of pea in his own words
15

16.  Initially, he selected large number of pea varities but in
his experiment, he used only the pure breds.
16

17.  He not only used
the normal Pisum
sativum but..
17

18.  Objective of the famous
experiment in his own
words
18

19. Not all characters could impress him
19

20. The Seven Characters which made History
20

21. 21

22. 22

23. 23

24. 24

25. 25

26. Ratios Mendel observed
26

27. 27

28. 28

30. Mendel did not directly present the
laws as they are now published in
books…
30

31. LAW OF SEGREGATION IN HIS WORDS
31

32. THE LAW OF INDEPENDENT ASSORTMENT
IN THE WORDS OF MENDEL
32

33. 33

34. 16 possible gametes
34

35. 35

36. 36

37. 37
•Mendel used Merkmal more than 150 times in his paper.
• In the “rediscovery” papers of 1900, this word often
was translated as “factor” or “determinant.”

38. Why pea became the star?
38

39.  Self-
Pollinated
 Grows
easily
 Contrasting
characters
 Large
flower
 Large seeds
 Short cycle
 Large
progeny
number
 Easy
emasculation
 Easy
pollination
 Less space
39

40. Character Dominant
form
Recessive
form
Gene
symbol &
chromosme
Seed shape Round form Wrinkled r (7)
Seed coat colour Grey White a (1)
Cotyledon colour Yellow Green i (1)
Pod colour Green Yellow gp (5)
Pod shape Full constricted v(4)
Position of
flower
Axial terminal fa (4)
Length of stem Tall dwarf le (4)
40

41. Mendel’s first law of inheritance
 Two alleles (factors) of a gene present in the F1 do not
contaminate each other.
 During gamete formation they separate and pass into
different gametes in their original form producing two
different types of gametes in equal proportion.
LAW OF
SEGREGATION Law of purity of
gametes
41

42. Explained with help of a monohybrid cross
Phenotypic
ratio-
3:1
Genotypic
ratio-
1:2:1
42

43. Mendel’s 2nd law of inheritance
 When two or more characters are inherited, individual
hereditary factors assort independently during gamete
production, giving different traits an equal opportunity of
occurring together.
 Thus, Segregation of two or more character in same hybrid
is independent of each other.
LAW OF
INDEPENDENT
ASSORTMENT
43

44. Explained with help of a dihybrid cross
Phenotypic
ratio-
9:3:3:1
Genotypic
ratio-
1:2:2:4:1:2:1:
2:1
44

45. Why Mendel’s predecessors failed?
No clear cut
class of
characters
Studied
plant as a
whole
Data and
record
keeping
inadequate
45

46. Less F2
plants
Quantitave
characters
No attempt
to study
frequencies
No complete
pollination
control
46

47. Why Mendel’s story is a success?
 Analysis of reasons of failures of earlier workers.
 Inheritance of one character at a time.
 Selection of garden pea.
 Knowledge of mathematics.
47

48.  Use of frequency relationships and statistics.
 Record keeping accurate.
 Formulated hypothesis and proved its correctness.
 Ignored characters not following his results.
48

49. 49
Why Mendel’s work
was overlooked?

50. 50
 Was Mendel ahead of his time?
 Did he have bad luck in some aspect?
 Mislead by Nageli to work on Hieraceum that did not
prove his theory?
 His paper was seen as essentially about hybridization
rather than inheritance?

51.  Mendel used mathematical principles of
probability.
 Mendel also did present his data in a way that was
a typical for a botanist.
 His work on discontinuous characters was
considered unimportant to Darwin, Galton and
others.
 Phenomenon of fertlization and behavior of
chromosomes was not known at that time.
51

52.  Mendels findings failed on Hieraceum due to presence
of apomixis and honey bees.
 Mendel did not publicise his findings through further
writting after his first paper.
 In the 1860's the hot topic was Charles Darwin’s
theory of evolution.
 His results were based on discontinuous variation
contrary to the continuous variation observable by many
biologists.
52

53. MENDEL DID NOT KNOW ABOUT
CHROMOSOMES
 Early 19th century Cells and nuclei simply pinched
in half to divide.
 Eduard Strassburger (1875) Gives clear and detailed
descriptions of cell division and chromosomes in
plants.
 Walther Flemming (1879-1882) Describes ‘Mitosis’
in animal cells
53

54.  Wilhelm Waldeyer (1888) Introduces the term
‘chromosome’.
 Gregor Johann Mendel (1865) formulated his laws
of heredity without the knowledge of
chromosomes.
 1900: When Mendel law were rediscovered, it
became clear that the behaviour of chromosomes
at cell division (mitosis and particular meiosis) was
exactly what was needed to explain the distribution
of hereditary factors.
54

55. The Rediscoverers
 Mendel’s laws were rediscovered independently within
two months of each other in Spring of 1900 by :
Hugo de Vries (Holland)
Carl Correns (Germany)
Erich von Tschermak (Austria)
55

56. Mendel was able to postulate that
 When two different characters are crossed, in F1
hybrids, the character that resembles one of the
parents termed dominant character masking the other
character.
 When two differentiating characters are crossed, in F1
hybrids, they remain together without mixing and in
further generations the characters separate completely
as one entity in each new progeny individual.
56

57.  When more than two differentiating characters are
crossed, in first generation hybrid they show
independent dominant effects and in further
generations each character assort independently in
each individual randomly with equal chance.
57

58. Implications of Mendelian
Inheritance in Genetics &
Plant breeding
58

59. From the concept of factors(alleles)
of a gene to the selection and
hybridization, the concept underlying
is given by the base of Mendelian
genetics.
59
MENDEL LAID
THE BASE OF
GENETICS AND
PLANT
BREEDING

60. Concept of homozygous and heterozygous
 What Mendel referred to as a “purebred” plant we now
know this to mean that the plant has two identical genes
for a particular trait.
 Eg. A purebred tall plant has two tall genes and a
purebred short plant has two short genes. The modern
scientific term for “purebred” is homozygous.
60

61.  This also forms the base of pureline theory which today
applies on selection of self-pollinated species.
 The plant breeding relies totally on the genetic base of
the plant before going for plant breeding methods which
differ for self pollinated and cross pollinated species.
61

62. Nature of gene action
 Dominace gene effect is likely to be selected for in cross
pollinated species whereas it is to be selected against in
self pollinated species.
 The selection is the heart of plant breeding.
 This concept relies on dominant and recessive gene
which is again the contribution of Mendelian genetics.
62

63. Concept of gene transfer
 Gene transfer allows introgression of a gene from a
superior or wild cultivar to a known variety.
 The concept of existence of genes and its particulate
nature was the contribution of Mendel, without which
gene transfer could not be thought of.
 Backcross method also relies on transfer of a gene
from the donor parent and then successive crosses with
recurrent parent which can only be performed due to
knowledge of genes.
63

64. Basis for Quantitative genetics
 Mendel's findings allowed scientists such
as Fisher and J.B.S. Haldane to predict
the expression of traits on the basis of
mathematical probabilities.
 Fisher(1918), showed that a large number
of Mendelian factors influencing a trait
would cause nearly continuous
distribution of trait values.
64

65. 65
 The famous Nilsson-Ehle and East’s experiment which proves
some genes to be quantitave: the results of the experiment are
based on mendelian inheritance.
Corolla length in Nicotiana
East concluded after his experiment:
 The F2 generation was much more variable than the the parents
and F1. This greater variability in F2 resulted from segregation
and recombination of Mendelian genes

66. The Chromosome Theory of Inheritance
 Walter Sutton and Theodor Boveri in 1903.
 Chromosome theory of inheritance states: There is a
parallelism between behavior of chromosomes and
Mendelian factors and chromosomes are carriers of
genetic material.
66
Mendelism + chromosomal theory = classical genetics

67. Similarities between Mendelian genes and
chromosomes
 The chromosomes occur in pairs like alleles of a gene.
 The homologous chromosomes separate during meiosis
like pair of similar or dissimilar alleles of a gene separate at
times of meiosis.
 Different chromosomes orient and separate during
meiosis showing parallelism with Mendelian factors.
 Fertilization restore diploid number of chromosomes, in
fertilized ovule.
67

68. 68

69. Pedigree Analysis and Genetic Disorders
 Pedigrees are diagrams that show relationships among the
members of a family of organisms.
 Dominant and recessive mutations and disorders can be
traced in families.
 The analysis of pedigrees allows genetic counselors to assess
the risk that an individual will inherit a particular trait.
 This can be used only due to knowledge and concept of
dominant and recessive alleles, which is the contribution of
Mendel only.
69

70. Deviations of Mendel’s Law
70

71. Incomplete dominace
 Phenomenon discovered by Correns in Mirabilis jalpa
(4-o’Clock plant).
 Expression of dominant gene is incomplete or partial.
 The type of relationship between alleles, with a
heterozygote phenotype intermediate between the two
homozygote phenotypes, is called incomplete
dominance.
71

72. 72

73. Overdominance
 Overdominance is the phenomenon in which a
heterozygote is more vigorous than both of the
corresponding homozygotes.
 „It is also called heterozygote advantage.
 „Example Sickle cell anemia
73

74. Resistant to malaria
SICKEL
CELL
ANEMIA
74

75. Linkage
 Tendency of DNA sequences to stay close together on
a chromosome and to be inherited together during
the meiosis phase of sexual reproduction.
 It is the most prominent exception to Mendel's Law of
Independent Assortment.
 In 1905, the British geneticists William Bateson, Edith
Rebecca Saunders and Reginald Punnett, cross-bred
pea plants in experiments similar to Mendel's.
75

76. 76

77. Why didn’t Mendel find linkage?
77
 Mendel was very fortunate not to run into the complication of
linkage during his experiments.
 Mendel worked with three genes in chromosome 4, two genes
in chromosome 1, and one gene in each of chromosome 5 and
7.
 In hundreds of crosses shown by the genetic map of the pea, two
characters(a and i) in chromosome 1 are so distantly located on
the chromosome that no linkage is normally detected. The same
is true for v or le on the one hand, and fa on the other, in
chromosome 4 and so on.

78. Eg)PHENYLKETONURIA (PKU)
Pleiotropy
78

79. PHENYLKETONURIA (PKU)
 This disorder is caused by a deficiency of
the enzyme phenylalanine hydroxylase, which is
necessary to convert the essential amino acid
phenylalanine to tyrosine.
 A defect in the single gene that codes for this
enzyme therefore results in the multiple
phenotypes associated with PKU, including
mental retardation, eczema, and pigment defects
that make affected individuals lighter skinned.
Eg.
79

80. 80

81. 81

82. 82

83. 83

84. 84

85. Conclusion
• Mendelian inheritance is the base of the science of
Genetics and Plant breeding.
• Though, Mendel did not present the laws of inheritance
as we know now, but these laws are the result of his
findings only.
• Mendel’s work could not be recognized in his era only
due to the reason that he was ahead of the time.
85

86. 86
 The knowledge of chromosomes lead to the
understanding of inheritance carriers as particles.
 Although, there may be some exceptions to the
Mendelian laws but at last they are only a few and they
are discovered only by keeping his findings as the base.
 Mendelian inheritance and the laws governing the
inheritance is the base of all activities in Genetics and
Plant Breeding.
---------------------------------------------

87. 87
MENDEL’S
MUSEUM

88. 88

89. There are hundreds of
Mendels working in
progress of science, the
irony is some would
never be recognized
and some would only be
recognized after they
die but,,,
“science remains
immortal”
89

90. 90