A tetrad is made of how many chromatids?

• A. Four chromatids
• B. Two chromatids
• C. One chromatid
• D. Eight chromatids

Answer: (A)

In meiosis, a tetrad forms when two homologous chromosomes pair up, and each chromosome has already been replicated into two sister chromatids. This means there are two homologous chromosomes, each with two sister chromatids, giving a total of four chromatids in the tetrad. This arrangement also allows crossing over to occur between non-sister chromatids of the homologs, which is a source of genetic variation. So the tetrad is made of four chromatids. Two chromatids would be just a single replicated chromosome, one chromatid would be an unreplicated chromosome, and eight chromatids would require more replicated chromosomes than are present in a typical tetrad.