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Does halacha permit or prohibit a Jew to genetically engineer an animal with the DNA of another kind of animal, or is this considered “Kilayim” the forbidden mixing of two animal species?

Sources for the answer please.

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Rabbi Kaganoff here makes an important initial definition that is a good starting point in answering your question:

It is important to clarify a common misconception. The prohibition of kilayim is not necessarily the creation of a new species — it is the appearance that one is mingling two species together. My desktop dictionary defines hybrid as “the offspring produced by breeding plants or animals of different varieties, species, or races.” Hybridization always involves making changes in the DNA of a species; most instances of kilayim do not. Planting seeds of different species in close proximity does not affect their genetic makeup – thus, technically, no hybridization transpires — yet it may be prohibited min haTorah. Similarly, wearing a garment manufactured from woolen and linen thread does not affect the two parent species or the DNA of the thread in the slightest.

Another good introductory piece is provided by Ariel Caplan here.

In his Part 2 here he helps to break down the issues at hand.

As far as the genetic engineering of animals, he points to the Chazon Ish:

Regarding crossbreeding animals, however, Chazon Ish takes a very different tack. He writes that artificial insemination is completely permitted, as actual mating is the only act prohibited as Kilayim of animals. It is clear from this ruling that transferring genes between animals would not constitute a violation of Kilayim, as no action of mating is involved.

He notes that there would be a difference in halacha viz-a-viz genetic engineering of animals vs plants:

The difference stems from the language used in the Pasuk in VaYikra 19:19: “Do not breed your animal as Kilayim, do not plant your field as Kilayim.” Rav Shlomo Zalman notes that the Torah focuses on the animals in the context of Kilayim of animals, whereas regarding Kilayim of plants the Torah focuses on the field itself being sown with multiple species. Hence, he concludes that only the union of two separate animal bodies would constitute a violation of Kilayim of animals, while Kilayim of plants is violated wherever a field is planted with two species. To frame the distinction in more conceptual terms, we might state that Kilayim of animals is defined by the action of mating two animals, while Kilayim of plants is defined by the result of two species planted in the same location.

So like the Chazon Ish, Rav Shlomo Zalman allows genetic engineering of animals and it would seem that the genetic engineering of plants poses a much greater halachic problem.

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