Video Transcript
In which phase of sperm production
does meiosis occur? (A) The multiplication phase, (B)
the growth phase, (C) the maturation phase, (D) the endocrine phase, or (E) the
metamorphosis phase.
To answer this question, let’s
recap the different phases of sperm production. The first phase is called the
multiplication phase. The multiplication phase involves
diploid primary germ cells dividing many times by mitosis and being converted into
diploid spermatogonia. Remember, most body cells are
diploid, which means that they contain two full sets of chromosomes, often
represented as two n. In humans, the diploid number is 46
chromosomes in each cell in total. However, in this diagram, we will
represent this as just four chromosomes.
The second phase is called the
growth phase. During the growth phase,
spermatogonia divide by mitosis and differentiate into primary spermatocytes, which
are also diploid. The primary spermatocytes also
replicate their genetic material at this point so that they are ready for
meiosis.
The third phase of spermatogenesis
is the maturation phase. This phase consists of two cellular
divisions called meiosis I and meiosis II. During meiosis I, the genetic
material in each primary spermatocyte is divided equally to form two cells called
secondary spermatocytes. The secondary spermatocytes are
haploid cells, which is often represented as n. Haploid cells contain only 23
chromosomes in humans, which is half the number of chromosomes of most other body
cells, including the primary spermatocytes that formed them. During meiosis II, the secondary
spermatocytes divide again to form haploid spermatids.
The final stage of sperm production
is the metamorphosis phase, during which the round spermatids develop
specializations, like tails, to become mature sperm cells.
Now we have enough information to
answer the question, which asks us to determine the stage of sperm production during
which meiosis occurs. Meiosis occurs during (C) the
maturation phase.
