Question

if a cell has 10 chromosomes to start, how many chromosomes will the cell have during anaphase?

Explanation:

Step1: Recall cell division (mitosis)

In mitosis, during anaphase, sister chromatids separate. If a cell starts with \( n = 10 \) chromosomes (diploid or haploid context, but for mitosis, starting with 10 chromosomes: each chromosome has two sister chromatids. In anaphase, when they separate, the number of chromosomes doubles temporarily. So initial chromosomes: 10, after separation (anaphase), each chromatid becomes a chromosome, so \( 10\times2 = 20 \)? Wait, no—wait, if the cell is undergoing mitosis, the starting number is the diploid number? Wait, no, let's clarify: If a cell has 10 chromosomes (so 10 chromatids? No, wait, a chromosome can be a single chromatid or two. Wait, in interphase, DNA replicates, so chromosomes become two sister chromatids. Then in mitosis, during anaphase, the sister chromatids separate, so each chromatid becomes a chromosome. So if the cell starts with 10 chromosomes (each as single chromatid, before replication), then after replication (prophase, metaphase), each chromosome has two chromatids. Then in anaphase, when they separate, the number of chromosomes becomes \( 10\times2 = 20 \), because each of the 10 chromosomes (with two chromatids) splits into two, so total chromosomes are 20. Wait, maybe the initial cell has 10 chromosomes (diploid, 2n=10? No, maybe 2n=10, so n=5? Wait, no, the question says "a cell has 10 chromosomes to start"—probably referring to the number of chromosomes in the cell before division. So in mitosis, during anaphase, the sister chromatids separate, so the number of chromosomes doubles. So 10 chromosomes (each with two chromatids) will have their chromatids separate, so each chromatid is a chromosome, so 10*2=20 chromosomes during anaphase.

Step2: Determine the answer

So the cell starts with 10 chromosomes. During anaphase (mitotic anaphase), sister chromatids separate, so the number of chromosomes becomes 20.

Answer:

20 (the option with 20)