This lesson is called "Genetic Testing for Family Planning," and is from the unit Gene Technology.

Hi there! My name's Mrs. McCready, and I'm here to guide you through today's lesson.

So thank you very much for joining me today.

In our lesson today, we're going to explain how genetic testing can be used in family planning, and discuss some of the difficult decisions parents may have to make.

Now, this is a really tricky and sensitive topic, so be prepared for a tough lesson today.

Now, in our lesson today, we're gonna come across a number of keywords, and they're listed up here on the screen for you now.

You may wish to pause a video and make a note of them, but I will introduce them to you as we come across them.

So first of all, we're going to have a look at how we test for heritable diseases before we consider how we might use that information to make decisions.

So are you ready to go? I certainly am.

So let's get started.

Now, the DNA of a human genome is wound into 23 pairs of chromosomes.

One of each of those pairs has come from your biological father and one from your biological mother.

Now, each chromosome in the pair has the same genes in the same positions.

But there are versions of genes, and these versions are called alleles.

And sometimes those alleles will be different and sometimes they will be the same.

So the chromosomes, the pair of chromosomes will have the same genes, but may will have different versions of those genes on them.

Now, for instance, in this example, we have the E version of the gene, the E allele, and this codes for wet earwax.

Whereas the e allele codes for dry earwax.

And depending on which combination you inherit, will depend on what type of earwax you have.

Now, some allele are dominant and some are recessive.

So dominant alleles are shown in uppercase, for instance, D, whereas recessive alleles are shown in lowercase, such as d.

Now, a person's phenotype will show the characteristics coded for by a dominant allele if they have: 1 copy of that allele, such as Dd, which is known as a heterozygous genotype, or if they have two copies of that allele, such as DD, which is known as a homozygous genotype.

Whereas a person's phenotype will only show the characteristic coded for by a recessive allele if there is no dominant allele present, for instance, dd.

Now, people who have got one recessive allele and one dominant allele, for instance, Dd, that's known as a heterozygous genotype, is called a carrier.

Now, they will not show the characteristic of the recessive allele, but they can pass that allele onto their offspring.

So let's quickly check our understanding.

A characteristic is caused by the recessive allele h.

Now, Alex has the genotype, Hh.

So which statements are true? a, Alex will show the characteristic, b, Alex is a carrier, c, Alex is homozygous, and d, Alex can pass the h allele to his offspring.

I'll give you five seconds to decide.

Okay, so you should have said that Alex is a carrier, and Alex can pass the h allele to his offspring as the statements that are true.

Well done if you got both of those right.

Now, humans reproduce sexually using gametes.

Now, female gametes are called egg cells, and male gametes are called sperm cells.

And each gamete carries only one chromosome from each pair.

Now, this means that each gamete only has one allele of each gene.

So let's have a look at that in a bit more detail.

This man's genotype is Ee.

Now, that means that some of the sperm he produces will have the E allele and some sperm will have the e allele.

Now, during sexual reproduction, either the E allele sperm or the e allele sperm, so either type of sperm could fertilise the egg cell from the mother.

And if the man has more than one child, some of his children may inherit the E allele and others may inherit the e allele.

So if a woman has the genotype Bb, which statement about her egg cells is true, is it a, all of her egg cells will have the genotype B, or b, all of her egg cells will have the genotype b, or c, all of her egg cells will have the genotype Bb, or d, some of her Excels will have the genotype B and some will have the genotype b.

I'll give you five seconds to decide.

Okay, so you should have chosen statement d, that some of her egg cells will have the genotype B and some will have the genotype b.

Well done if you spotted that as true.

Now, some alleles cause inherited conditions that affect our health.

And we can use a form of testing called genetic testing to detect the presence of these alleles in a person's genome.

Now, genetic testing can be done on any sample of blood or saliva or other body fluids which contains cells where DNA is stored.

Now, people with a family history, so that's parents and grandparents who have an inherited condition, may well choose to get a genetic test done before they have children.

Now, by doing this, the genetic test can show whether they have the dominant or the recessive all for a particular condition.

How many copies of that alleles they have, in other words, whether they are heterozygous or homozygous.

And this information can then be used to guide their decision making.

Now, we can use a Punnet square to model how the inheritance of these alleles will go from the parents down to their offspring.

So if a father's genotype is Dd, and a mother's genotype is dd.

And if we put that into a Punnet square where the gametes are on the sides and the possible genotypes of the offspring are in the central squares, and write them out.

So the mother's genotype is dd, and the father's genotype is Dd.

And then we cross them.

We'll get Dd in the first square, the D coming from the dad, the d coming from the mum, Dd in the next square, dd in the third, and dd in the fourth square.

And we can use that data in the central part of the Punnet square to identify the possibility of the offspring having certain genotypes and therefore having certain phenotypes and the chance of that happening.

So let's have a look at that in a bit more detail using a condition called polydactyly.

Now, polydactyly is an inherited condition that causes people to have extra fingers or toes.

And you can see in the picture there, the feet of a man who has polydactyly.

So instead of having five toes on each foot, he has six toes on each foot, and that condition is called polydactyly.

Now, it is caused by a dominant allele.

Give that the letter D.

Now, genetic testing can show that a man has Dd genotype, so he is heterozygous, that perhaps a woman has the genotype dd, so she is homozygous recessive.

And if we put those data into a Punnet square where the mother is dd, and the father is Dd, and cross those letters by each other, we'll see that we have two squares of Dd and two squares of dd.

So we can then use that information to identify the probability, the chance that their child will inherit the genotype Dd, and therefore have polydactyly, because polydactyly is a dominant condition and therefore only one copy of the allele is required for a person to have the condition.

And we can see that there are two out of the four, which have Dd, which have the D allele present in them.

So there is a two in four chance of a child of theirs having polydactyly.

That means there is also a 0.

5 chance of having a child which develops polydactyly.

So we can use the Punnet square in simple genetic cases such as this to identify the chance of a child inheriting a condition from its parents if we know what the parents' genotypes are.

So let's have a look at this again.

So we know that polydactyly is caused by a dominant allele D.

And genetic testing shows that a man and a woman both have the genotype Dd.

So what is the probability that their child will have polydactyly? So use the punnet square results there to decide what is the probability that their child will have polydactyly.

And I'll give you five seconds to decide.

Okay, so you can see there that there is one case of homozygous dominant, DD.

There are two cases of Dd, the heterozygous version, and there is one case of the homozygous recessive version, dd.

So that means that with a dominant condition, there is a probability of 0.

75 that they will have a child who also has polydactyly.

Well done if you worked that out correctly.

Now, cystic fibrosis is an inherited condition that causes problems with breathing and with digestion, and it is caused by a recessive allele f.

So a couple are planning to have a baby, and they have had some genetic testing done, and this shows that the man has the genotype FF, and a woman has the genotype Ff.

So what I would like you to do please, is to firstly complete a Punnet square for this couple.

Use f for the recessive cystic fibrosis allele and F for the dominant allele.

Then I would like you to calculate the probability that their child will have the genotype FF, homozygous dominant.

Then calculate the probability that their child will be a carrier, and then calculate what the probability will be that their child will have cystic fibrosis.

Remembering that cystic fibrosis is a recessive condition.

So pause the video whilst you work that out and come back to me when you are ready.

Okay, let's check our work.

So firstly, I asked you to complete a Punnet square for this couple.

So you should have included Ff for the mother and FF for the father, crossed those against each other and shown that there are two out of four chances of having a child with FF and two outta four chances of having a child with Ff.

So the probability of their child being homozygous dominant FF is two in four, or 0.

5 probability.

The probability that their child will be a carrier, so that is heterozygous Ff.

So that is a probability of two in four as well, or probability of 0.

5.

And what is the probability that their child will have cystic fibrosis? Well, that would require a genotype of ff of which there is no chance, and therefore zero probability.

Well done if you calculated all of those correctly.

So we've seen how we can test for heritable alleles.

Now, let's see how we can use that data to make some difficult decisions.

Now, the results of genetic testing may show that somebody who is planning to have a baby could pass on alleles that could affect their baby's health.

And this is likely to be very worrying for the parents and therefore having the opportunity for them to discuss this information and their thoughts on it with a doctor or a genetic counsellor will be very important because by doing so, that helps them to firstly ensure that they have interpreted the results correctly, and then that they have used that information and assessed the probability of having an affected child and understood that probability correctly.

And then they can also make sure that they find appropriate advice and sources of support to help them through the next stages of decision making and pregnancy.

Now, people need to make their own decision about whether or not to try to get pregnant in the light of being shown that they have alleles that could be detrimental to their baby's health.

And this is a very personal decision.

It's a very difficult decision to make and one that cannot be rushed despite the pressures that might surround the parents.

Now, genetic testing results are very useful sources of information.

And in the UK, the NHS runs these tests, and there is a very high rate of accuracy, but it is not 100%.

And therefore with any test, there is always a very small risk of either getting a false negative.

So that means that they get a test result that shows that they do not have the allele when in fact they actually do.

That's called a false negative.

Or a small risk of getting a false positive result.

And this is a test result which shows them to have the allele when they don't in fact have it.

That's called a false positive result.

Now, that information has to be taken into account when a couple decide whether or not to have a baby.

So let's check our understanding here.

Genetic tests are always 100% accurate.

True or false? So you should have said that that is false.

But why? So you should have explained that by saying that they have a high rate of accuracy.

But there is a very small risk of getting a false negative or a false positive result.

Well done if you've got both of those points.

Now, a couple may decide to go ahead and try to get pregnant even after they have had genetic testing, which shows that they could pass on alleles which could negatively affect their baby's health.

So this couple is continuing their discussion and the woman says, "We know there's a chance our baby could inherit a genetic condition, but when will we know if it has? And this sense of urgency and worry is really quite palpable.

Now, if genetic tests of the parents show that there is a high probability that the child could be born with a genetic condition that will cause ill health, then further genetic testing will be offered.

And further tests are not compulsory.

So the parents have to decide whether they're going to have them or not.

And then obviously if they do, what they're gonna do with that data once they get it.

So let's have a look at some ways in which that further data can be obtained.

Firstly, let's have a look at embryo screening.

Now, embryo screening is also known as pre-implantation genetic testing, PGT.

And this is done as part of in vitro fertilisation.

So as part of the process of going through IVF, embryo screening is performed as part of that.

So what happens in IVF is that in a lab, sperm from the father is used to fertilise eggs from the mother.

And after a few days, this fertilised egg has divided a few times.

And from that point, some of the cells can be removed from the embryo and tested genetically.

And embryos which do not have particular alleles are then implanted into the mother and grow on to become a foetus.

So embryos which have alleles for particular diseases will be screened out of the IVF process at this point before implantation.

Now, some people have ethical questions about embryo screening.

For instance, this gentleman asks, is it wrong to pick and choose embryos? Don't they all have a right to live? Now, an ethical question is a question about whether something is right or wrong.

But there is not necessarily any one correct answer, and what might feel best for one person may not feel best for somebody else.

And just because that is the case doesn't mean to say that one person is right or wrong, it just means they have different perspectives on the same issue.

Now, there are other forms of genetic testing, one of which is called chorionic villus sampling.

Now, chorionic villus sampling is done during pregnancy at between 11 and 14 weeks of pregnancy.

And what happens is that, so a sample is taken from the placenta.

A part of the placenta actually called the chorionic villus, which is why it's called chorionic villus sampling.

Now, the placenta is the part which connects the baby to the mother's circulatory system, but it's foetal cells that it's made up of.

And so a sample of those foetal cells can be taken from the placenta and tested.

Genetic testing is done using the DNA from those placental cells.

Now, with chorionic villus sampling, there is a 0.

5 to 1% risk of miscarriage, and there is also a small risk of infection.

Both factors need to be considered as part of the decision making when deciding whether to have chorionic villus sampling.

There's also another form of genetic testing called amniocentesis.

Now, this is done slightly later on in pregnancy at between 15 and 20 weeks.

And this is where a sample of the amniotic fluid which is surrounding the foetus is removed and tested.

So the foetus is growing within the amniotic sac and that amniotic sac is filled with a fluid, the amniotic fluid, and a sample of that is removed and tested.

And because that contains foetal cells, it can then be tested genetically using genetic testing.

Now, with this procedure, there is a 0.

5% risk of miscarriage, and there is also a small risk of infection.

Again, factors that need to be considered when deciding whether or not to have this procedure.

So, let's check our understanding.

What is embryo screening? Is it, a, selecting IVF embryos that do not have particular alleles? Is it b, testing the amniotic fluid after the embryo has become a foetus? Or is it c, sampling cells from the placenta after the embryo has become a foetus? I'll give you five seconds to decide.

So embryo screening is the first statement, and this is also called pre-implantation genetic testing, or PGT.

Now, statement b is referring to amniocentesis and statement c is referring to chorionic villus sampling.

So well done if you spotted all of those correctly.

Now, sometimes genetic testing during pregnancy shows a high probability that the child will be born with a genetic condition that will lead to its ill health.

So continuing with this scenario, this gentleman now knows, but asks what happens next? Now, counselling and ongoing support are offered to all parents within this situation.

And the results of the genetic testing enable both the parents and medical staff to plan ahead for what might come to make sure that the baby and the parents are supported through the pregnancy, the birth and life beyond that, and can make sure that their needs are provided for.

So there's lots of things that happen next.

Some of these decisions are really difficult to make.

Some parents may think about whether to continue with the pregnancy or to have an abortion, and that is a really difficult decision to make as well.

And as this woman says, "Is having an abortion wrong?" Again, this is an ethical question about what is right or wrong, and it can be really difficult to answer this.

Now, nobody can force a parent to decide one way or another, to decide to have an abortion or not.

And there is lots of support available so they can make the decision that feels best for them and their future child.

But she also asks, "If I have the baby, will the genetic condition cause my child to suffer?" Now, this is a very understandable and natural thing to be worried about, to be worried about your future child's health and happiness is something that all parents will experience.

But it's reassuring to know that many people with genetic conditions live very happy fulfilling lives, and ultimately, it's up to society to remove disabling barriers such as physical and social barriers to enable people who do have genetic conditions to live full and fulfilling lives.

So let's just check our understanding again.

Who asks an ethical question here? So Lucas says, "What is the probability that the child will have a genetic condition?" Jun asks, "Is it right to have an abortion?" And Sophia asks, "What can we do to support the child as it grows up?" But who is asking an ethical question? Okay, so, hopefully, you've identified that it's Jun who is asking an ethical question.

Lucas is asking a factual question, and Sophia is asking a pragmatic question about support.

Well done if you spotted that.

So what I'd like you to do now is to firstly explain what is meant by embryo screening or pre-implantation genetic testing.

Then I would like you to state one ethical question related to embryo screening.

Then I'd like you to complete the table to identify the risks and the benefits of genetic testing during pregnancy.

So that was the chorionic villus sampling and the amniocentesis procedures.

And then I'd like you to consider Izzy.

So she's worried and she says, "If I get pregnant and genetic testing shows the baby has a genetic condition that will affect its health, will I have to have an abortion?" So what I'd like you to do is to write some advice to reassure Izzy.

So pause the video whilst you are considering all of those and come back to me when you are ready.

Okay, let's review your work.

So firstly, I asked you to explain what is meant by embryo screening, or PGT.

So you should have said that firstly, it is offered to parents if there is a high probability that their child could be born with a genetic condition that will cause ill health.

And it happens during IVF, during in vitro fertilisation.

And in this procedure, the sperm from the father is used to fertilise the eggs from the mother in a lab.

And after a few days after the cell has divided, cells are then removed from the embryos and genetic testing is completed.

And embryos that do not have the alleles associated with the genetic condition are implanted into the mother.

And those that do have the allele are discarded at this point.

So that's embryo screening or PGT.

Did you get all of those notes down? Well done if you did and do add to your notes if you've missed anything out.

Then I asked you to state one ethical question related to embryo screening.

So you might have said, for example, is it wrong to select which embryo is implanted? Or maybe is it wrong to destroy embryos that are not selected? Or perhaps you wrote, do all embryos have a right to live? Or maybe you asked a similar question, which is of an ethical nature.

Then I asked you to complete the table to identify risks and benefits of genetic testing during pregnancy.

In particular, these two testing procedures, chorionic villus sampling and amniocentesis.

Now, they both have risks of miscarriage of between 0.

5 and 1%, and they also both carry a small risk of infection.

But what about the benefits of these genetic tests? Well, you should have said that this allows parents and medical staff to plan ahead and make sure that the baby and the parents are supported and their needs are met.

Then I asked you to write some advice to reassure Izzy.

So you might have said that an abortion is only one option that some parents consider, but nobody can force you to make that decision one way or another.

And that there is also counselling and other ongoing support offered to all parents in this situation.

Now, many mothers decide to continue with their pregnancy after a positive genetic test, and many people live with genetic conditions very happily.

Now, the results of the genetic test mean you'll be able to plan ahead to make sure the needs of the child and your needs are met if you do decide to go ahead with the pregnancy.

So there's lots of support there, lots of advice that can reassure anyone in this situation.

And well done for writing that.

Okay, we've come to the end of our lesson now, and it's quite a challenging series of scenarios to consider.

So well done for handling it so sensitively.

Now, we've seen today how some alleles are associated with conditions that affect people's health, such as polydactyly and cystic fibrosis.

Now, people planning to have a baby can undergo genetic testing to work out the probability of their child inheriting these alleles or being a carrier.

Now, embryo screening uses genetic testing to select embryos without these alleles.

And then a foetus can be tested for the presence of these alleles during pregnancy by one of two methods, either chorionic villus sampling or amniocentesis.

Now, genetic tests can have false negatives and false positive results, and they also carry the risk of miscarriage or infection.

So there are some negative considerations to bear in mind.

And it's also extremely important that parents are supported whilst they are interpreting the genetic test results because they are complex results with complex probabilities surrounding them.

And there are many ethical questions that get thrown up by these scenarios that make it very difficult to make personal decisions, and therefore support is extremely necessary.

So I hope you found today's lesson interesting.

It's certainly very challenging, but well done for handling it so well.

Thank you very much for joining me today, and I hope to see you again soon.

Bye!.