Video Transcript
The stages of the second meiotic
division are as follows: prophase II, metaphase II, anaphase II, telophase II. What stage of meiosis is shown in
the diagram?
Meiosis is a form of cell division
that produces gametes for sexual reproduction. There are two separate divisions in
meiosis called meiosis I and meiosis II. We start with two copies of 23
chromosomes, or 46 in total. Before meiosis, these 46
chromosomes are copied, or duplicated, to form a duplicated chromosome
structure. This happens during interphase. After this stage, meiosis I can
begin.
We’ll represent these two sets of
duplicated chromosomes as pink and blue. Rather than drawing out 46
chromosomes, let’s represent this by showing two chromosome pairs. After meiosis I, these two sets of
23 chromosomes are split into two cells. After meiosis II, these duplicated
chromosomes are separated as single, unduplicated chromosomes into a total of four
cells, as we can see here.
In order to answer this question,
let’s look at the stages of meiosis II in more detail, using this cell as an
example. This is the cell we’ll be starting
with. Notice it has two duplicated
chromosomes, one in pink and one in blue. This is to represent the mix of 23
chromosomes in this cell. The first step of meiosis II is
called prophase II. Here, the spindle fibers begin to
form, and the nuclear membrane breaks down.
Then, in metaphase II, the
duplicated chromosomes are lined up along the equator of the cell. In anaphase II, the duplicated
chromosomes are pulled apart by the spindle fibers. So a single chromosome, or
chromatid, is brought to opposite poles of the cell. Then, in telophase II, the nuclear
membrane reforms around the separated chromosomes and the cells divide. So these two cells that form now
have 23 single, unduplicated chromosomes. The same process of meiosis II
occurs in the second cell that’s produced from meiosis I. In total, four cells are
produced.
After seeing all the stages of
meiosis II, we can now answer our question. The stage of meiosis II, as shown
in the provided diagram, is metaphase II.
