Clonal Selection Flashcards
1
Q
Bud-Sport
(Bud Mutation)
A
- when a mutant suddenly appears in the branch of a plant
- Sports are generally unwanted, but have been the source of many new cultivars
- a sudden change in a single branch due to a mutation apparently arising from a single bud
2
Q
Chimera
A
- A plant composed of a mixture of two genotypes, each expressed independently in separate layers of the shoot
- the different genotypes originate within the meristematic tissue
3
Q
Environment by Genotype Interactions
A
- a source of phenotypic variation
- clones gron in different environments may look different
- plant size, shape, flower number and color may all be different in plants grown in the sun versus in the shade
4
Q
Genetic Mosaics
A
- a source of phenotypic variation
- permanent genetic variation
- 4 ways:
- variegation - the cellular-based cotrasting genetic expression in different parts of the same organ, usually caused by chimeras
- patterend genes - a differential gene expression that is not due to cell arrangement
- transposons - a unique kind of genetic element in cells of some organisms that have the capacity to change position within the chromosome
- somaclonal variation - pathogens that infect the cells of a plant and spread throughout the plant, where they remain infective
5
Q
Genetic Variation
A
- one type of clonal variation (phenotypic variation is the other)
- Mutation - a permanent gentic change involving some part of the DNA molecule
- Bud-Sport - a sudden change in a single branch due to a mutation apparently arising from a single bud
- plants or seeds can be treated with chemicals or radiation to induce mutations
6
Q
Graft Chimera
A
- a chimera sometimes created when an adventitious shoot emerges from callus at a graft that has tissues of both the stock and scion
7
Q
Mericlinal Chimeral
A
- the mutant cells are only in a part of a single cell layer
- unstable
- thought of as a transition as cells divide to form a periclinal chimera or revert to a non-mutant form
8
Q
Monoculture
A
- the mass production of a single genotype within a singl planting
- since all the plants of a nursery, field orchard, or plantationhave the same genotype, each is equally vulerable to specific environmental hazards and specific pests and diseases and may lead to an overall loss of genetic diversity
9
Q
Patterned Genes for Variegation
A
- a differential gene expression (as a color pattern) that is not due to cell arrangement
- a genetic trait of the cultivar
- an inherited trait
- can be fixed by selection and seed propagation
- the pattern is different due to different cells in a tissue expressing color genes
- their typical pattern is displayed throughout the clone and expressed by each plant
- not a chimera
10
Q
Periclinal Chimera
A
- all the cells in one layer different from the other layers
- the most stable chimera
- common cause of leaf veriegation
11
Q
Phenotypic Variation
A
- one type of clonal variation (genetic variation is the other)
- involves a change in the way a plant’s genes are expressed
- is not a mutation
- sources of phenotypic variation:
- environment by genotypic interactions (phenological changes)
- ontogenetic aging (phase changes)
- permanent genetic variation
- infection by systemic pathogens (particularly viruses and similar organisms)
12
Q
Reversion
A
- a shoot which emerges from inner tissue of a chimera and shows the genotype of the inner tissue
13
Q
Sectorial Chimera
A
- the mutated tissue occupies a sector that encompasses all layers
- not stable
- would revert to a periclinal chimera or an all- mutant or non-mutant meristem
- an unusual chimera
14
Q
Systemic Pathogen Infection
A
- usually infection of a plant with a pathogen causes sever symptoms and can lead to plant death
- however, some viral infection cause only limited vigor loss
- n some cases they cause a variegated leaf or flower cover and are prepuated during propagation
15
Q
Transposon
A
- a moveable genetic element
- also called jumping genes
- they randomly move about the chromosome creating genetic mosaics
- A mobile genetic factor or jumping gene that turns on or off a gene resulting in a new phenotype
- the variegation pattern is inherited from seed (chimera not inherited from seed)