Advanced Placement (AP) Biology Practice Exam

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Which structure contains 4 chromatids that forms when homologs pair during meiosis?

Chromosome
Tetrad
Chromatid
Gene

The correct answer is: Tetrad

The structure that contains four chromatids and forms when homologous chromosomes pair during meiosis is known as a tetrad. During prophase I of meiosis, homologous chromosomes—each consisting of two sister chromatids—come together and align closely. This pairing of the homologous chromosomes, each made up of two sister chromatids, results in the formation of a tetrad, which effectively consists of four chromatids. This arrangement is critical for processes such as crossing over, where genetic material is exchanged between the homologous chromosomes, increasing genetic diversity in the resulting gametes. Understanding the significance of tetrads in meiosis is essential in grasping how genetic variation occurs during reproduction.