Video Transcript
Which cells in the seminiferous
tubules divide by mitosis to form spermatogonia? (A) Primary spermatocytes, (B)
spermatids, (C) Sertoli cells, (D) interstitial cells, or (E) primordial germ
cells.
The seminiferous tubules are
located in the testes of the biological male and are the site of sperm production,
which is sometimes known as spermatogenesis. Overall, spermatogenesis converts
diploid primordial germ cells, which are sometimes called primary germ cells, into
haploid mature sperm cells.
You might recall that a diploid
cell is one, like most other body cells, that contains two sets of chromosomes,
which is often represented as 2n. In humans, diploid cells have 46
chromosomes in total. But here we have simplified the
diploid chromosome number in the primordial germ cells to show just four
chromosomes.
A haploid cell, on the other hand,
contains half this number of chromosomes, which is often represented as n. This haploid chromosome number is
23 in humans. But in this diagram, it is
represented as two chromosomes.
The formation of haploid gametes,
which are the sperm cells in biological males and egg cells in biological females,
is important, as when they fuse together in fertilization, they form a diploid
zygote with a full set of chromosomes. Let’s take a look at the cells that
are produced in the stages of spermatogenesis so we can work out which cells divide
by mitosis to form spermatogonia.
The first stage of spermatogenesis
is called the multiplication phase, and it involves diploid primordial germ cells
dividing by mitosis. The cells that are produced are
called spermatogonia, or a singular spermatogonium. And these cells are also diploid as
they were formed through mitosis. The spermatogonia then enter the
growth phase, where they divide by mitosis again and are converted into diploid
primary spermatocytes.
The primary spermatocytes then
enter the maturation phase, where they begin meiosis, which you might recall halves
the number of chromosomes in a cell, as it includes two cellular divisions: meiosis
one and meiosis two. Meiosis one converts the primary
spermatocytes into haploid secondary spermatocytes, and meiosis two converts the
secondary spermatocytes into haploid spermatids. The spermatids then specialize to
form mature sperm cells through the final stage of spermatogenesis, the
metamorphosis phase.
If we take a look back at the
question, we are looking for the cells in the seminiferous tubules that divide by
mitosis to form spermatogonia. We can see that the correct answer
is option (E), primordial germ cells.
