Self-Incompatibility
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Question No. 1
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Self-incompatibility in some plants occurs because pollen tube growth fails in similar genetic types. What might be missing in this interaction?
A.
Genetic mutations blocking pollen development
B.
Physical barriers in the flower’s reproductive parts
C.
Substances needed to promote pollen tube growth
D.
Enzymes that inhibit pollen germination
Question No. 2
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What mechanism could prevent self-fertilization by stopping pollen tube growth through a reaction between identical genetic factors?
A.
Lack of nutrients in the pistil
B.
Production of inhibitory compounds when similar alleles interact
C.
Enhanced pollen germination due to diverse alleles
D.
Mechanical obstruction in the ovary
Question No. 3
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Where does the reaction stopping pollen germination typically occur in plants with stigma-based self-incompatibility?
A.
Within the style
B.
On the stigma surface
C.
Inside the ovary
D.
In the pollen itself
Question No. 4
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In plants where pollen tubes are blocked in the style, what characterizes this type of self-incompatibility?
A.
Pollen fails to stick to the stigma
B.
Pollen tubes grow abnormally or rupture in the style
C.
Tubes reach the ovary but cannot fertilize
D.
Germination is prevented at the stigma
Question No. 5
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What happens in plants where self-incompatibility occurs only after pollen tubes reach the ovary?
A.
Tubes fail to penetrate the ovule or release sperm
B.
Pollen germination is blocked on the stigma
C.
Tubes stop growing in the style
D.
Pollen degrades before reaching the flower
Question No. 6
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How does pollinating immature buds help bypass self-incompatibility?
A.
It uses pollen from another species
B.
It applies pollen to buds before incompatibility develops
C.
It enhances pistil maturity
D.
It increases pollen viability with hormones
Question No. 7
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What allows delayed pollination to sometimes result in self-fertilization?
A.
Using aged pistils with fresh pollen
B.
Pollinating buds early with mature pollen
C.
Applying heat to the flower
D.
Using pollen from late-season blooms
Question No. 8
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Why might self-fertilization occur more often at the end of the flowering season?
A.
Flowers become more receptive
B.
Pollen production increases
C.
Incompatibility factors weaken or disappear
D.
Environmental conditions improve
Question No. 9
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How can exposing flowers to radiation overcome self-incompatibility?
A.
It changes the genetic makeup of incompatibility alleles
B.
It destroys pollen grains
C.
It alters the pistil’s structure
D.
It raises flower temperature
Question No. 10
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What effect does high temperature have on overcoming self-incompatibility in some plants?
A.
It boosts pollen survival
B.
It inactivates enzymes causing the incompatibility reaction
C.
It shortens the style
D.
It promotes growth factor production
Question No. 11
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How does removing part of the style help achieve fertilization in self-incompatible plants?
A.
It shortens the pollen tube’s journey
B.
It bypasses the region blocking pollen
C.
It triggers growth factor release
D.
It increases moisture around the flower
Question No. 12
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What technique involves placing pollen directly onto ovules to avoid self-incompatibility?
A.
Controlled environment pollination
B.
Direct ovule pollination
C.
Cross-species pollination
D.
Chemical treatment of the style
Question No. 13
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Why is self-incompatibility valuable for creating hybrid seeds in breeding programs?
A.
It increases crop yield directly
B.
It allows hybrids without manual pollen control
C.
It maintains uniform parent lines
D.
It selects for disease-resistant plants
Question No. 14
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In breeding, how does self-incompatibility assist in mixing desirable traits?
A.
Through forced self-pollination
B.
By enabling natural cross-pollination
C.
Via genetic modification
D.
Using artificial pollination only
Question No. 15
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What environmental challenge can disrupt self-incompatibility in breeding?
A.
Low genetic diversity
B.
Breakdown under specific temperature or humidity conditions
C.
Need for large plant populations
D.
High mutation rates
Question No. 16
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Why is it hard to create uniform inbred lines in plants with self-incompatibility?
A.
Self-pollination doesn’t produce seeds
B.
The pollen mutates frequently
C.
It requires specific pollinators
D.
Plants are too sensitive to weather
Question No. 17
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Which of the following best explains the role of self-incompatibility in plants?
A.
Promotes autogamy for pure line selection
B.
Encourages inbreeding to fix traits
C.
Prevents self-fertilization to increase genetic diversity
D.
Ensures seed development without pollination
Question No. 18
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What happens when a self-incompatible plant is pollinated with its own pollen?
A.
It produces more seeds
B.
Fertilization occurs but seeds are non-viable
C.
No seed is formed despite functional pollen
D.
It forms hybrid seeds
Question No. 19
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Which scientist coined the term 'self incompatibility'?
A.
East
B.
Koelreuter
C.
Stout
D.
Brewbaker
Question No. 20
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In gametophytic self-incompatibility, compatibility is determined by which factor?
A.
Style genotype
B.
Stigma morphology
C.
Pollen parent genotype
D.
Genetic constitution of the pollen
Question No. 21
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What is a major genetic outcome of self-incompatibility in crop plants?
A.
Enhanced homozygosity
B.
Reduction in genetic variation
C.
High heterozygosity through outbreeding
D.
Stable self-pollination mechanism
Question No. 22
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What type of floral morphology is associated with heteromorphic self-incompatibility?
A.
Similar styles and stamens
B.
Monomorphic pollen
C.
Different lengths of style and stamen
D.
Unisexual flowers
Question No. 23
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In Primula, what is the expected ratio of thrum and pin flowers in F1 generation from a thrum × pin cross?
A.
1:2
B.
2:1
C.
1:1
D.
3:1
Question No. 24
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Which family is known to exhibit distyly with short and long styles?
A.
Lamiaceae
B.
Fabaceae
C.
Primulaceae
D.
Solanaceae
Question No. 25
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Which term best describes a system where styles and stamens occur in three different positions?
A.
Homostyly
B.
Distyly
C.
Tristyly
D.
Unistylism
Question No. 26
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What is a supergene in the context of Primula self-incompatibility?
A.
Gene that expresses in ovary only
B.
Set of genes governing flower morphology and incompatibility
C.
A gene responsible for male sterility
D.
A mutated allele that causes sterility
Question No. 27
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What cytological difference exists between pollen of pin and thrum flowers?
A.
Pin has three nuclei; thrum has two
B.
Pin pollen is larger than thrum
C.
Thrum has three nuclei; pin has two
D.
There is no cytological difference
Question No. 28
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Which type of incompatibility is controlled by the genotype of the pollen-producing plant rather than the pollen itself?
A.
Sporophytic
B.
Gametophytic
C.
Homomorphic
D.
Morphological
Question No. 29
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What causes the rejection of pollen in self-incompatible plants?
A.
Lack of pollen production
B.
Incompatibility reaction between pollen and style tissues
C.
Absence of ovule development
D.
Stigma shape differences
Question No. 30
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Which floral trait differs between pin and thrum flowers besides style length?
A.
Color of petals
B.
Number of sepals
C.
Anther height
D.
Number of ovules
Question No. 31
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Which feature is NOT a consequence of self-incompatibility in crops?
A.
Maintenance of heterozygosity
B.
Promotion of inbreeding
C.
Inhibition of self-pollination
D.
Encouragement of cross-pollination
Question No. 32
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Which system exhibits pollen-stigma inhibition due to dominance hierarchies in alleles?
A.
Gametophytic
B.
Both systems
C.
Sporophytic
D.
Neither
Question No. 33
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In which system are homozygous offspring possible through specific crosses?
A.
Gametophytic
B.
Sporophytic
C.
Both systems
D.
Neither
Question No. 34
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Which plant is an example of gametophytic self-incompatibility?
A.
Cabbage
B.
Radish
C.
Rye
D.
Sunflower
Question No. 35
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Where does inhibition occur in gametophytic self-incompatibility?
A.
Stigma
B.
Style
C.
Ovary
D.
Pollen tube
Question No. 36
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What determines incompatibility in sporophytic systems?
A.
Pollen's own genotype
B.
Parent plant's genotype
C.
Environmental factors
D.
Both A and B
Question No. 37
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Which system involves trinucleate pollen grains?
A.
Gametophytic
B.
Sporophytic
C.
Both
D.
Neither
Question No. 38
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Reciprocal crosses showing fertility differences are characteristic of which system?
A.
Gametophytic
B.
Neither
C.
Sporophytic
D.
Both systems
Question No. 39
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When do biochemical incompatibility factors develop in sporophytic systems?
A.
During pollen formation
B.
After pollination
C.
Before pollen formation
D.
At fertilization
Question No. 40
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Which system involves dry stigmas with direct pollen-papillae interactions?
A.
Gametophytic
B.
Both systems
C.
Sporophytic
D.
Neither
Question No. 41
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Who discovered the sporophytic self-incompatibility mechanism?
A.
Darwin
B.
Hughes
C.
Lamdgust
D.
Besdap-Harrison
Question No. 42
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Which system allows parental genotype recovery in crosses?
A.
Gametophytic
B.
Sporophytic
C.
Both
D.
Neither
Question No. 43
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Incompatibility due to shared alleles in pollen and stigma occurs in which system?
A.
Gametophytic
B.
Sporophytic
C.
Both
D.
Neither
Question No. 44
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Which system shows pollen tube inhibition only if alleles differ in the style?
A.
Sporophytic
B.
Gametophytic
C.
Both
D.
Neither
Question No. 45
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Which crop uses sporophytic self-incompatibility?
A.
Rye
B.
Red Clover
C.
Cabbage
D.
Sunflower
Question No. 46
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Dominance of alleles (e.g., S1 over S2) affects compatibility in which system?
A.
Gametophytic
B.
Sporophytic
C.
Both
D.
Neither
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