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（单词翻译）
In mammals, the sex of a baby is determined1 by the combination of chromosomes3 it inherits from its parents. Nearly every cell in a male body has two different sex chromosomes–one is shaped like an X and one is shaped like a Y. Females also have two sex chromosomes in each cell but they are both X-shaped. When the male sperm4 and the female egg come together, each one contributes one sex chromosome2. The female always contributes an X chromosome while the male can provide either an X or a Y. If the male provides an X then the embryo5 has two X chromosomes and becomes a female. If the male provides a Y then the embryo has one of each and grows into a male.
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