Discuss how constraints related to biology and management affect the choice of a crossbreeding system. Please be descriptive.

Some important constraints:  

-Plant breeding: autogamy and allogamy, self-sterility, etc  

-Animal breeding:  trait compatibility

- Breeding systems in general (i.e., both in plants and animals): barriers for sexual reproduction  

Explanation:

Crossbreeding systems consist of the breeding between two breeds in order to develop progeny with particular advantageous phenotypic traits. In-plant crossbreeding systems, it is imperative to have into account whether the plant is autogamous (reproducing by self-pollination) or allogamous (reproducing by cross-fertilization), because it will affect the fitness of the progeny resulting from these breeds. Moreover, the biological mechanisms of self sterility and compatibility must be also taken into consideration. In-animal breeding systems, it is important to have into consideration that phenotypic traits we desire to obtain in the progeny must be compatible between races. In addition, the barriers for sexual reproduction are also an important issue both in plant and animal breeding systems, it thus being impossible, for example, to get a breeding between Chihuahua and Great Dane dogs.

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i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.