To check an egg for chromosomal abnormalities, doctors use a laser to make a small incision in the outer membrane, which allows them to extract the polar body and the chromosomes it contains.

为了检查一个卵细胞的染色体是否异常，医生用激光在卵细胞外膜上切一小口，通过这个小口抽取极体及其所含的染色体。

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The human cell nucleus contains 23 pairs of chromosomes, which carry genetic information necessary for developing and running the body correctly.

BBC: NEWS | Health | Gene fault increases leprosy risk