F1 hybrid
From Freepedia
F1 hybrids are the first generation seeds/plants or animal offspring resulting from a cross mating of distinctly different parental types, the offspring of which produce a new, uniform variety with specific characteristics from both parents. In fish breeding, those parents frequently are two closely related fish species, while in plant and animal genetics those parents usually are two inbred lines. Mules are F1 hybrids between horse and donkey. Crossing specific parent plants produces a hybrid seed (plant) by means of controlled pollination. To produce consistent F1 hybrids, the original cross must be repeated each season. As in the original cross, in plants this is usually done through controlled hand-pollination, and explains why F1-seeds are so expensive.
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Production of F1 hybrids
In plants
Two populations of breeding stock with desired characteristics are subject to inbreeding until the homozygocy of the population exceeds a certain level, usually 90% or more. Typically this requires more than ten generations. After this happens, both populations must be crossed while avoiding self-fertilization. Normally this happens in plants by deactivating or removing male flowers from one population, taking advantage of time differences between male and female flowering or hand-pollinating[1].
In animals
Commonly breeded fish species as well as all mammals and birds are not hermaphrodite, like most plants are, and therefore it is much more easy to prevent self-fertilization during a F1 cross. F1 crosses in fish can be between two inbred lines or between two closely related fish species, like between cichlid subspecies.[2]. The cross usually is performed by natural or artificial insemination.
Advantages
- Homogenity and predictability - because of the homozygocy of the parent pure lines, there is next to none genetic variation between individual plants or animals. This makes their phenotype extremely uniform and thus attractive for mechanical operations and makes it easier to fine-tune the management of the population. Once the characteristics of the cross are known, repeating this cross will yield exactly the same result.
- Higher performance - As all not junk DNA alleles codify for a certain version of a protein or enzyme, having two different versions of this allele amounts in having two different versions of the enzyme. This will increase the likelyhood of having an optimal version of the enzyme present and reduce the likelyhood of a genetic defect. This effect is referred to in genetics as the genetic hysteresis effect.
Disadvantages
- The main advantage of F1 hybrids is their drawback as well. When F1 cultivars are used for the breeding of a new generation, their offspring will revert to the natural level of heterozygocy and thus will have a depression in yield. Of course, this is a desired characteristic from the point of view of the seed producer.
- Both inbreeding as well as crossing both lines requires a lot of work, which translates in a much higher seeds cost. In general, the higher yield offsets this disadvantage.
