Polyploidy PPT BY :- Dr.Pinky Diwedi

1. Mendelian Genetics
Topics:
-Transmission of DNA during cell division
Mitosis and Meiosis
- Segregation
- Sex linkage (problem: how to get a white-eyed female)
- Inheritance and probability
- Independent Assortment
- Mendelian genetics in humans
- Linkage
- Gene mapping
-Gene mapping in other organisms
(fungi, bacteria)
- Extensions to Mendelian Genetics
- Gene mutation
- Chromosome mutation
(- Quantitative and population genetics)
B2900
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2. Polyploidy
• M.Sc.II sem, Paper-204, unit-V
• M.Sc. III sem,Paper-303,unit-IV
• Dr.Pinky Dwivedi

3. Mutation
Source of genetic variation:
Gene Mutation
- somatic, germinal
Chromosome mutations (Ch. 11)
- structure (deletion, duplication, inversion, translocation)
- number
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4. Chromosome Mutation
(2. changes in number)
Euploidy: variation in complete sets of
chromosomes
Aneuploidy: variation in parts of chromosome
sets

5. Euploidy
1x monoploid (1 set) = n
2x diploid (2 sets) = 2n
3x triploid
4x tetraploid
5x pentaploid polyploid (> 2 sets)
6x hexaploid
n = # chromosomes
in the gametes
2n 4n

7. Polyploids
Autopolyploids: within one species
Allopolyploids: from different, closely
related species

8. Polyploids
Larger
than Diploids

9. Polyploids
Triploids: = 3n
- problems with pairing during
meiosis
- unbalanced gametes
- usually sterile
Applications: seedless fruits, sterile fish
aquaculture

10. Formation of Triploids
n
n
n
= 3n
n
Polar
bodies
n 2n
n
= 3n

11. Triploids (3x)
Why can’t a triploid produce viable
gametes ?

12. Fig. 11-5

13. Triploids (3x)
x = 1 Gametes

14. Triploids
x = 2
Gametes
or
viable
Non-
viable

15. Viable Gametes from Triploids
Probability
(2x or x gamete) =
( )
if x = 10 Prob. = 0.002
of viable gametes
1
2
x - 1
0
0.1
0.2
0.3
0.4
0.5
0 5 10 15 20 25 30 35
Number of Chromosomes
Probability
of
Viable
Gametes
# of chrs
2
3
4

16. Triploid Fish
Frankenfish-Biotech
3n carp

17. Autotetraploid

19. Autotetraploid
Doubling of chromosomes: 2x----> 4x
Even number of chromosomes: normal meiosis
2<---->2 segregation------> functional gametes

20. Polyploids
Autopolyploids: within one species
Allopolyploids: from different, closely
related species
Hybridization

21. Triploid
2n = 42 x = 7
n = 21
2n = 14, n = x = 7
Chromosome
sets:
A, B, D
7 7 7
hybrid
Origin of
Wheat
Fig. 11-10
2n = 28
n = 14
7 14
Allopolyploid

22. Polyploidy
Plants: speciation (wheat)
Animals: - rare (sex determination)
- fish (salmon: tetraploid)
- parthenogenetic animals
123 11 22 12 12

23. Latitute North
30 40 50 60 70 80 90
%
Polyploids
30
40
50
60
70
80
90
Plant Polyploids

24. Chromosome Mutation
(changes in number)
Euploidy: variation in complete sets of
chromosomes
Aneuploidy: variation in parts of chromosome
sets
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25. Aneuploidy
Nullisomics (2n - 2)
Monosomics (2n - 1)
Trisomics (2n + 1)
normal

27. Aneuploidy
Nullisomics (2n - 2)
- lethal in diploids
- tolerated in polyploids
Monosomics (2n - 1)
- disturbs chromosome balance
- recessive lethals hemizygous
Trisomics (2n + 1)
- sex chromosomes vs autosomes
- size of chromosome

30. Aneuploidy
Non-disjunction: Gametes
Meiosis I n + 1 n - 1
Meiosis II n + 1 n - 1 n
n x n - 1 ---------> 2n - 1 monosomic
n x n + 1 ---------> 2n + 1 trisomic

31. Human Aneuploids
13
18
21 X Y

32. Aneuploidy
Humans: (live births)
Monosomics - XO Turner syndrome
- no known autosomes
Trisomics XXY Klinefelter sterile male
XYY fertile male ( X or Y gametes)
XXX sometimes normal
21 Down
18 Edwards syndromes
13 Patau

33. Maternal Age (years)
20 25 30 35 40 45 50
Downs
Births
per
1000
0
5
10
15
20
25
Downs Births per 1000
2 %

34. 0.62 % 50 %

35. Mutations Causing Death and
Disease in Humans
% of live births
Gene mutations: 1.2
Chromosome mutations: 0.61

36. Chromosome Mutations
(Humans)
% of spontaneous abortions
Trisomics 26 %
XO 9 %
Triploids 9 %
Tetraploids 3 %
Others 3 %
Chromosome 50 %
abnormalities

37. Chromosome Mutations
Comparison of euploidy with aneuploidy
Aneuploids more abnormal than euploids:
likely due to gene imbalance
Plants more tolerant than animals to
aneuploidy and polyploidy
(animal sex determination)

38. Summary
Mutation - gene
- chromosome
(structure, number)
Detecting - cytology
- phenotype
Rate of mutation - low
Mutation - source of genetic variation
- evolutionary change
genetic
analysis

39. Chapter References
Mitosis and Meiosis
Ch. 4 p. 100 – 112 Prob: 10, 11, 12, 18, 19
Mendelian Inheritance
Ch. 5 p. 118 – 129 Prob: 1 – 3, 5, 6, 7, 8, 9
Recombination, linkage maps
Ch. 6 p. 148 – 165 Prob: 1-5, 7, 8, 10, 11, 14
Extensions to Mendelian Genetics
Ch. 14 p. 459 – 473 Prob: 2, 3, 4, 5, 6, 7
Chromosome Mutations
Ch. 11 p. 350 – 377 Prob: 1, 2

40. Mendelian Genetics
Topics:
-Transmission of DNA during cell division
Mitosis and Meiosis
- Segregation
- Sex linkage
- Inheritance and probability
- Independent Assortment
- Mendelian genetics in humans
- Linkage
- Gene mapping
-Gene mapping in other organisms
(fungi, bacteria)
- Extensions to Mendelian Genetics
- Gene mutation
- Chromosome mutation
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41. Genetics
Part I Part II
Molecular Mendelian

42. Chromosome Theory of
Inheritance
- genes organized into chromosomes
- correlation: Genetics & Cytology
- theory can explain segregation and
independent assortment

43. Two types of nuclear division
1. Mitosis (somatic tissue)
2. Meiosis (germ tissue)

44. Mendelian Genetics
• Meiosis and mitosis
• Segregation and independent assortment
• Sex linkage, sex determination
• Pedigrees
• Linkage, recombination and linkage maps

45. Mendelian Genetics
• Gene linkage: 3 point test cross, tetrad analysis
• Extensions (dominance, multiple alleles, pleiotropy, epistasis,
penetrance and expressivity)
• Mutation: gene mutation
chromosome mutation (number
structure)

46. Mendelian Genetics
Applications
Genetic markers as tools:
- human diseases
- population genetics
- genetic structure (gene flow)
- systematics and phylogeny
- forensics

47. Mendelian Genetics
in Humans
Determining mode of inheritance
Problems:
1. long generation time
2. can not control matings
Alternative:
* information from matings that have
already occurred “Pedigree”

48. Human Pedigrees
Pedigree analysis:
• trace inheritance of disease or condition
• provide clues for mode of inheritance
• however, some pedigrees ambiguous

49. Human Pedigrees
Pedigree analysis:
dominant vs recessive
autosomal vs sex linked

50. Linkage:
Human Genetic Diseases
Linkage:
• organization of genes and genome
• marker genes linked to:
Disease genes

51. Mutation
Gene Mutation
- somatic, germinal
- detecting mutations
Chromosome mutations
- structure
- number

52. Chromosome Mutation
(changes in number)
Euploidy: variation in complete sets of
chromosomes
Aneuploidy: variation in parts of chromosome
sets