Question

in which parts of the cell cycle would chromosomes be paired up? check all that apply.
□ interphase
□ metaphase i
□ anaphase ii
□ telophase ii
□ metaphase ii
□ telophase i

Explanation:

1. Interphase: Chromosomes are replicated (forming sister chromatids, but not paired with homologous chromosomes in the way of synapsis here; however, in the context of meiosis, the pairing of homologous chromosomes starts after interphase in prophase I, but interphase is where DNA replication for future pairing occurs. Wait, actually, the pairing (synapsis) of homologous chromosomes happens in prophase I of meiosis. But the options given include metaphase I. Let's re - evaluate:

• Metaphase I (Meiosis): In metaphase I of meiosis, homologous chromosomes (paired during prophase I) line up at the metaphase plate. So chromosomes are paired (homologous pairs) in metaphase I.
• Telophase I: At telophase I, the homologous chromosomes have been separated to opposite poles, and the cells are preparing to divide. The chromosomes are no longer paired in the same cell (as the cell is about to split into two haploid cells).
• Anaphase II: In anaphase II of meiosis, sister chromatids are separating. The chromosomes are not paired (homologous chromosomes were already separated in meiosis I, and now sister chromatids are separating).
• Telophase II: Similar to telophase I but for the second meiotic division. Chromosomes are not paired.
• Metaphase II: In metaphase II, chromosomes (sister chromatids) line up at the metaphase plate, but they are not paired with homologous chromosomes (since homologous chromosomes were separated in meiosis I).
• So the correct phase where chromosomes are paired (homologous pairs) is metaphase I. Also, interphase is the stage before meiosis where DNA replication occurs, and the homologous chromosomes are present in the cell (but not yet paired in the synapsed way). Wait, the question is about "chromosomes paired up". The pairing (synapsis) of homologous chromosomes occurs in prophase I, and they remain paired (attached at chiasmata) until anaphase I. So in metaphase I, the paired homologous chromosomes line up at the metaphase plate. So among the given options, metaphase I is the stage where chromosomes are paired. Also, if we consider the initial state, in interphase, the chromosomes are in the form of chromatin, and after replication, sister chromatids are formed, but homologous chromosomes are present in the cell (but not paired in the synapsed way). However, the main stage where homologous chromosomes are paired (synapsed) and remain paired during the metaphase stage is metaphase I.

Answer:

• metaphase I (the checkbox next to "metaphase I" should be checked)