Video Transcript
In this video, we’ll learn about
artificial, or assisted, reproduction and the process of in vitro fertilization. We’ll also learn about the role of
gamete banks and how they can be used to preserve gametes like sperm or eggs. Then, we’ll discuss how somatic
cell nuclear transfer, or renucleation, can be used to clone organisms. So let’s give Mr. sperm and Ms. egg
some privacy and start this lesson.
Artificial, or assisted,
reproduction is the use of medical technology to create a pregnancy. It is primarily used to help treat
infertility. Infertility is a disease that
prevents pregnancy despite repeated attempts at conception. There could be many different
reasons for this. For example, in the female
reproductive system, an egg is normally released from the ovary, which then travels
through the Fallopian tube where it may encounter a sperm after sexual
intercourse. This sperm can then fertilize the
egg. You’ll recall that fertilization is
the process where an egg cell and a sperm cell combine to form an embryo. This embryo can then implant into
the uterine wall, where it can give rise to a pregnancy.
But what happens if this Fallopian
tube is blocked? Then this egg won’t be able to pass
through and neither will the sperm. In this situation, fertilization
inside the body may not happen. So a technique called in vitro
fertilization, or IVF, can be used to fertilize the egg outside the body in the
laboratory. Here, an embryo can be formed in
the lab, which can then be transferred back inside the body where it can implant and
give rise to a pregnancy. Because embryos are formed outside
the body, the children conceived by IVF are sometimes called test-tube babies. However, this term is not commonly
used anymore as the embryos are quickly transferred to the uterus where they
continue to develop.
Now, let’s take a closer look at
the steps involved in IVF. The first step of IVF is ovarian
stimulation, where the female takes hormones in order to stimulate the production of
eggs in the ovaries. One of the ovaries are indicated
here. Let’s take a closer look at what
happens during ovarian stimulation. Eggs develop within the ovaries in
fluid-filled sacs called follicles. This follicle grows over time as
the egg matures. Normally, only a single egg matures
during a menstrual cycle. However, by taking additional
hormones during IVF, this can allow multiple follicles and multiple eggs to
mature.
Once the follicles have grown
sufficiently, the eggs are ready to be extracted. In a medical setting and normally
under anesthesia, a long needle attached to a test tube is inserted into the ovary
and into the follicle. This needle is attached to a pump
that sucks the follicular fluid from the follicles along with the egg that’s
inside. This follicular fluid is collected
inside of a test tube. These test tubes can then be poured
into large plastic dishes called petri dishes and can be searched using a microscope
to find the eggs.
Once the eggs are collected, the
next step is to collect the sperm. Sperm are contained in the semen,
which is collected after ejaculation into a specimen cup. The semen is then processed in
order to remove much of the fluid and to concentrate the sperm. Once concentrated, the sperm can be
used for fertilization. Now that we’ve extracted the sperm
and eggs, in the next step of IVF, these two gametes are combined in the lab for
fertilization. This can actually be done in two
major ways. Using the traditional method, sperm
can simply be added to the eggs in a petri dish. This is done inside drops using a
special liquid called culture media. This culture media contains all the
salts and nutrients that are optimal for fertilization to occur. Inside these drops, the sperm
penetrates the egg and fertilization occurs.
Another method is called
intracellular sperm injection, or ICSI for short. Here, a sperm is placed inside a
tiny needle and injected directly into the egg. This second technique can be useful
when there’s only a small number of sperm available. Once the eggs are injected, they
can also be placed into a petri dish. In both cases, these petri dishes
are then placed into a warm incubator that is meant to mimic the conditions inside a
human body. This is known as culturing the
embryos. And in this ideal environment in
the incubator, the embryos will grow and develop over time. First, the fertilized egg divides
into two cells, which then divides into four cells, which then goes on to form a
specialized structure called the blastocyst. These contain hundreds of cells and
measure just about a tenth of a millimeter.
Blastocysts typically take about
five days to form. This blastocyst can then be
transferred into the uterus in the final step of the IVF process. During the embryo transfer, the
embryo is loaded into a catheter. This is then placed inside of the
uterus where the embryo is deposited. Over time, the embryo can implant
into the uterine wall where it can give rise to a pregnancy. IVF has helped many couples
overcome infertility, but it isn’t a guarantee. And typically, the highest success
rates are seen in younger people. For this reason, the use of gamete
banks can be very useful. Eggs and sperm can be frozen and
kept in liquid nitrogen for long-term storage in so-called egg or sperm banks.
The main advantage of gamete
banking is to preserve fertility, and there’s multiple applications for this. For example, for those who wanna
postpone having a family in order to focus on their careers, for instance, can
preserve their fertility by freezing their gametes. This involves the same steps as
shown earlier with ovarian stimulation and egg extraction in females and sperm
extraction in males. But these gametes can then be
processed and frozen in liquid nitrogen. This way, 10 years later or even
longer, they can come back and have their younger and healthier gametes thawed and
used for IVF with a better chance for success.
Gamete banking is also useful for
those undergoing medical treatments where there is a possibility of reduced
fertility or sterility, for example, for those recently diagnosed with cancer and
who are preparing for chemotherapy. Cancer is a disease of cell
division where our tumor cell can divide uncontrollably. This uncontrollable cell division
can be stopped using chemotherapy. Chemotherapy is a medical treatment
that involves the administration of drugs that impair cell division. Although gametes don’t divide the
same way cancer cells do, chemotherapy can still stop gametes from completing their
cell division. And in this case, it may be
recommended that the patient freeze their gametes before they start
chemotherapy.
Besides humans, animals can also
benefit from gamete banking. Many animals, like this panda here,
are listed as endangered species. And without intervention, these
species could become extinct. By extracting their gametes and
freezing them, this can help protect their species. Suppose by some cruel twist of fate
that the panda suddenly went extinct. We can then follow the panda
gametes and form embryos using IVF. These embryos can then be
transferred into an appropriate surrogate, like a close relative of the panda. And this might bring the panda
back.
However, this isn’t our only option
for saving the panda. There is another way; we can make a
clone of a panda using a technology called somatic cell nuclear transfer. A single body cell, or somatic
cell, contains all the information for the development of this panda. In the DNA, that’s found in the
nucleus of the cell. Therefore, it’s possible to make a
clone of the panda from this cell.
To perform this technique, an egg
cell is also needed. First, we need to isolate the
nucleus from the somatic cell. Then, the nucleus from the egg cell
is removed, which can now be called an enucleated egg cell. Then, the isolated nucleus from the
somatic cell is transferred to the enucleated egg cell. This cell can then be stimulated in
the lab to ultimately turn it into an embryo that can give rise to a baby panda
that’s a clone of the original panda from which the somatic cell is derived.
This all sounds a bit like science
fiction, but it has been done successfully in a number of animals, like cattle,
frogs, and sheep. You may have heard of Dolly the
sheep. In 1996, Dolly was the first mammal
cloned. And because of this and all the
media attention she received, she’s been called the world’s most famous sheep. The cloning process was highly
inefficient at the time and it took close to 300 attempts before it worked with
Dolly. Dolly died in 2003 due to causes
unrelated to the cloning, but her tissue was used to make additional clones named
Daisy, Debbie, Denise, and Diana. As of 2016, all of the sheep were
alive and well. For ethical reasons, the
application of this technique for human reproduction is prohibited, and its use for
research remains strictly regulated.
Now, let’s look at a practice
question to see how much we’ve learned about assisted reproduction.
What is stored at very cold
temperatures in gamete banks? Fertilized eggs, embryos, sperm
only, unfertilized eggs and sperm, or unfertilized eggs only.
This question is asking us about
gamete banks and what’s stored in them. A gamete bank is a facility where
gametes are stored at very low temperatures, usually using liquid nitrogen. This is often used as a method for
fertility preservation. For example, somebody who was
recently diagnosed with cancer may need to have their eggs or sperm preserved
because the chemotherapy treatment may make them sterile. Their gametes can be extracted and
then processed and frozen at either an egg bank or a sperm bank. These gametes can be stored for a
long time in these conditions. And once the individual is ready to
build a family, they could thaw them.
Since these gametes are outside the
body, a special procedure called in vitro fertilization, or IVF, may be needed to
fertilize the eggs to create embryos. The embryo created during IVF can
then be transferred to the uterus where it can implant and give rise to a
pregnancy. Now, let’s review these answer
choices to see which one best answers this question. The answer “fertilized eggs” is not
correct because a fertilized egg is not a gamete. Although these can be stored at IVF
clinics, generally fertilized eggs would not be stored in a gamete bank. “Embryos” is also incorrect because
again they aren’t gametes. These can also be frozen and stored
in liquid nitrogen, although this is generally done using an IVF clinic and not a
gamete bank.
“Sperm only” is only partially
correct since sperm can be stored in a sperm bank, which is a kind of gamete bank,
although eggs can also be stored in gamete banks. So let’s see if there’s a better
answer. “Unfertilized eggs and sperm” seems
like a good choice since they’re both gametes and they can both be stored at either
egg or sperm banks, which are both gamete banks. “Unfertilized eggs only” is only
partially correct since unfertilized eggs are gametes, but sperm can also be stored
at gamete banks. Therefore, the answer that best
describes what’s stored at gamete banks is “unfertilized eggs and sperm.”
Let’s look at some of the key
points that we’ve addressed in this video. Assisted reproduction is the use of
medical or scientific technology to create a pregnancy. In humans, it’s often used to treat
infertility. A common procedure used is in vitro
fertilization, or IVF, where fertilization takes place outside the body. The steps include ovarian
stimulation, egg extraction, sperm extraction, fertilization, embryo culture, and
embryo transfer. We also learned that gametes like
eggs and sperm can be stored in gamete banks for fertility preservation. And finally, we learned about
somatic cell nuclear transfer, or renucleation, which is a technique that can be
used to clone organisms.