Genetic systems of forest trees

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document in English

biology

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published 25/11/2008

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The term ‘genetic system’ was coined in 1932 by C.D. Darlington, one of the renowned pioneers of cytogenetics. His original deﬁnition was limited: Properties of heredity and variation, methods of reproduction and the control of breeding, we now realize, are in various ways bound up together in each group of organisms. They constitute a genetic system. The genetic systems of different groups of organisms differ widely. The concept and its deﬁnition have later been elaborated as follows. Genetic system refers to any of the species-speciﬁc ways of organization and transmission of the genetic material, which determines the balance between coherence and recombination of genes and control the amount and type of gene combinations. Evolution of the genetic systems means the evolution of those mechanisms effecting and affecting genetic variability. The genetic information in the nucleus is packed in structures called chromosomes. Each chromosome contains genes in a linear arrangement, with its genes linked together in a consistent sequence, such that the gene programming a given protein (and all its resulting functions) is at a particular position or locus within its chromosome. For higher plants the basic state is diploid, such that there are two homologous versions of each chromosome, one from the mother and another from the father.

Introduction.
Cytological factors.
Mating pattern and gene flow.
1. The mating pattern.
2. Outcrossing plant species.
3. Metandry.
4. Wind pollination - characteristic of gymnosperms.
5. Self-incompatibility and embryonic lethals.
Mode of reproduction.
Isolation.
1. Spatial isolation.
2. Temporal isolation.
3. Incompatibility.
4. Hybrid sterility.
Forest trees.
1. Conifers.
2. Angiosperms.
Conclusion.