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.