Question

why are some chromatids referred to as recombinant?
they are genetically identical.
they belong to different species.
they result from crossing over.
they are abnormal in structure.

Explanation:

Recombinant chromatids are formed during meiosis when crossing - over occurs. Crossing - over is the exchange of genetic material between homologous chromosomes. This exchange leads to new combinations of alleles on the chromatids.

• "They are genetically identical" is incorrect because recombinant chromatids have new genetic combinations.
• "They belong to different species" is not relevant as the concept of recombinant chromatids is within a species during meiosis.
• "They are abnormal in structure" is wrong; they are a normal result of genetic recombination.

Answer:

They result from crossing over.