Hi, I'm Mrs. Hudson, and today I'm going to be teaching you a lesson called "Errors in Cell Division and Cancer: The Basics." This is a biology lesson and it comes under the unit titled, "Cell Division: Mitosis and Meiosis." The outcome of today's lesson is I can describe cancer including benign and malignant tumours and identify potential risk factors for cancer.

On this slide here, you can see the key words for today's lesson, and they are mitosis, genes, tumour, benign, and malignant.

Let's have a closer look at what those words mean.

So mitosis is a type of cell division that produces genetically identical cells.

Genes are short sections of DNA that code for a specific characteristic or protein.

Tumour is a mass of cells that have been produced through uncontrolled cell division.

Benign is a tumour that is non-cancerous and contained to one area.

And finally, malignant is a tumour that is cancerous and can spread.

If you want to pause the video to make a note of those keywords, please do, and then press play when you're ready to continue.

Today's lesson is going to be split up into three different parts.

In the first part of the lesson, we're going to be looking at cancer and cell division, and then we're going to look at the difference between benign and malignant tumours.

And then in the final part of the lesson, we're going to look at risk factors for cancer.

But let's get going with the first part of the lesson, cancer and cell division.

Most cells in the body use a process called mitosis to divide and produce new cells.

Mitosis is needed in multicellular organisms for growth and repair of damaged tissue.

So here we've got a picture of a seedling.

This is in a plant.

A plant is multicellular, and you can see there that that seed is growing.

So the growth of a seedling into a plant will require new cells, which are made through mitosis.

And here we can see an X-ray that's showing a broken arm, and new cells will be made through mitosis to heal the bone.

So repair and replacement of cells also requires mitosis.

Mitosis forms part of the cell cycle, and the cell cycle is regulated by genes to ensure that cells only divide when they need to and stop dividing when necessary.

So this image here is showing you the cell cycle, and the cell cycle produces new cells through cell division.

But it's really important in multicellular organisms that the cell cycle is regulated, and this is to make sure that cells don't divide uncontrollably, that we only make new cells when the body needs them, and that any cells that are made that potentially are defective, so the DNA is not quite right, that those cells will self-destruct.

And also, we need to make sure that cell division stops when it needs to.

This here is showing you a gene.

A gene is a short section of DNA that codes for a characteristic or protein, and genes are involved in the regulation of the cell cycle.

So what we can see here is that we've got a gene which got a tick next to it, which is showing that some genes promote the cell cycle and encourage cell division, whereas other genes stop the cell cycle and reduce cell division.

So genes are involved in the regulation of the cell cycle.

Let's just do a quick check for understanding before we move on.

So first question, in multicellular organisms, which process produces new cells for growth and repair? A, meiosis, B, mitosis, or C, reproduction? This is B, mitosis.

Fantastic job if you got that right.

Next question.

What regulates the cell cycle? A, hormones, B, mitosis, or C, genes? This is, C, genes, and remember that genes are short sections of DNA.

Cancer is caused by changes to the DNA of a cell that leads to uncontrolled cell division and cell growth.

Uncontrolled cell division can lead to the formation of a tumour and mass of cells.

So what happens here is some cells have DNA that is damaged, and that might potentially mean that some of the genes that regulate cell division are changed, and therefore cells start to divide uncontrollably which leads to the formation of a tumour.

So here we've got an image which is showing you healthy cell division, and you've got a cell which is healthy, and that cell will divide, and it will lead to controlled cell division with healthy tissue being formed where the cell cycle is being regulated In uncontrolled cell division, you have a healthy cell to begin with, but then there's a change to the DNA of that cell, which leads to uncontrolled cell division and the formation of a tumour, which is a mass of cells.

And if the DNA of all of those cells is damaged, then those cells will keep dividing uncontrollably.

Uncontrolled cell division can lead to the formation of a tumour, which is a mass of cells.

And we can see here we've got an image, which is showing you some healthy cells and also the formation of unhealthy cells where DNA has changed, leading to a tumour.

The tumour cells will continue to divide uncontrollably, making the tumour grow larger.

So we can see on this image here, it lines there pointing to the cells with changes in DNA, which is leading to uncontrolled cell division.

And then we will end up with the formation of a tumour, which is a mass of cells.

Now surrounding that tumour, you do have healthy cells where there is controlled cell division.

So it's important to know the difference between healthy cells with controlled cell division and tumours which are caused by cells with changed DNA with uncontrolled cell division.

Let's do another quick check for understanding.

Which two factors cause tumours and cancer to develop? A, uncontrolled cell division, B, changes to the DNA of cells, or C, a sudden reduction in cell division.

This is A and B.

So tumours developed due to uncontrolled cell division and that uncontrolled cell division is caused by changes to the DNA of cells.

We're ready now to move on to the first task of today's lesson.

So your job in part one is to complete the table to show if each statement is true or false.

Then in the second part of task A, you're going to rewrite each false statement in the table to make it true.

So these are the statements that you have ticked as being false in part one of task A and rewrite those statements to make them true.

And then in the third part of task A, you're going to annotate the diagram to show how tumours form.

There are labels on there already to help you.

I'm sure you're gonna do a fabulous job.

Pause the video and then press play when you're ready for me to go through the answers.

Let's see how we did.

So in the first statement, that is false.

So cancer is caused by changes in the DNA of a cell, and this leads to cell division stopping.

That is not true.

A tumour is a mass of cells formed by uncontrolled cell division.

That is true.

The cell cycle is not normally regulated.

That is false.

And mitosis forms part of the cell cycle and is used in multicellular organisms for growth and repair.

This is true.

So for the second part of the task, we're going to be looking at the first statement, and the third statement, and correct those to make them right.

So for the first statement, cancer is caused by changes in the DNA of cells.

That was correct, but the incorrect part was saying that it leads to cell division stopping, but actually this leads to uncontrolled cell division.

So well done if you manage to recognise that.

And then the second statement, the cell cycle is regulated by genes, and some genes promote the cell cycle and other genes stop the cell cycle and cell division.

And then finally, for part three, annotating this diagram to show how a tumour forms, you've got healthy cells with controlled division.

So those are on the left-hand side of this diagram.

Then on the right hand side, those lines are pointing to the cells that are part of the tumour, and those cells have changes in the DNA leading to uncontrolled cell division.

And then final label is the formation of a tumour, which is a mass of cells.

There's obviously quite a lot of information there.

If you need to pause the video to add anything into your answer, give it extra detail, then please do.

But well done because we're ready to move on to the second part of our lesson.

So we know about cancer and cell division now.

let's move on to look at benign and malignant tumours.

Not all tumours are cancerous.

There are two different types of tumour, benign and malignant.

This image here is showing you a benign tumour, and benign tumours are not cancerous.

And this image is showing you a malignant tumour.

Malignant tumours are cancerous.

So the two types of tumour are benign and malignant.

Benign tumours are not cancerous.

Malignant tumours are cancerous, and they can spread around the body.

Let's look at benign tumours in a little bit more detail.

Benign tumours are growths of abnormal cells which are contained within one area.

They usually grow slowly.

Benign tumours are usually contained within a membrane and do not invade neighbouring tissues.

So here we can see that is the benign tumour, which is a growth of abnormal cells that divide uncontrollably.

So the DNA of those cells has changed, and there is still uncontrolled cell division.

But the key difference here is that there is a membrane surrounding that benign tumour.

And because there is this membrane, it means that neighbouring tissues are not invaded.

And this is important because it means that the tumour cannot spread to neighbouring tissues.

Now let's look at malignant tumours.

Malignant tumours are cancerous.

They are not contained within one area and usually grow quickly.

For this reason, they are quite dangerous.

So here we've got a picture of a malignant tumour and the line there is pointing to malignant tumour cell, and this is where there's growth of abnormal cells that divide uncontrollably.

So the DNA of those cells has been changed and they are still dividing uncontrollably, but the difference is that malignant tumours invade neighbouring tissue and can spread to other parts of the body where they form secondary tumours, and this is called metastasis.

So here the neighbouring tissue is invaded as the tumour is not held within a membrane.

And then what else can happen is that malignant cells can break off and they spread to form secondary tumours, which is called metastasis.

Let's check our understanding.

So this is a true or false question.

Benign tumours are cancerous, true or false.

And then justify your answer.

A, benign tumour cells are contained within a membrane and do not invade neighbouring tissue, or B, benign tumours can invade neighbouring tissue and spread to other parts of the body.

Benign tumours are cancerous.

This is false, and the justification is, A, benign tumours cells are contained within a membrane, so therefore they do not invade neighbouring tissue.

Well done if you got that right.

Malignant tumours are dangerous because they invade healthy neighbouring cells.

This means they are more likely to affect the function of the organ that they originate in.

So here we've got a picture of some lungs, and the first picture is showing you healthy lungs where there is controlled cell division, and there is no tumours being formed.

In the second image, we can see that there is some lungs with tumour formation.

So those lungs have got cells where the DNA has changed, there is uncontrolled cell division, and there are tumours present.

Now, if those tumours are malignant, they're not contained within a membrane.

What this means is that those tumour cells can invade neighbouring tissue.

And what will happen over time is, in picture three, the tumours will have invaded the healthy lung cells and spread around the lungs, which will affect how the organ functions.

Malignant tumours are also dangerous because the tumour cells can enter the blood and lymphatic system.

So if you look at this picture here, which is showing you the stages of malignant tumour growth, you can see the darker coloured cells are the malignant cells and they start off quite small.

But because of the uncontrolled cell division, it grows in size.

And they're not contained within a membrane, so they start to invade the surrounding tissue.

And on the diagram, you can see the green kind of line at the bottom that is showing you the blood or the lymph vessel.

And eventually as that malignant tumour grows, the tumour cells can invade the blood or the lymph vessel, so those malignant cells get into the blood or the lymph vessels.

And cells in the blood and the lymphatic system can travel all around the body, allowing the cancer to spread further.

So the reason why malignant tumours are very dangerous is because they can get into the blood and the lymph vessels, which can travel all around the body, and that can result in secondary tumour formation.

Let's do another check for understanding now.

Which two statements explain why malignant tumours are dangerous? A, they are contained within a membrane, B, they invade neighbouring healthy tissue, or C, they can enter the blood and lymphatic system.

There's two answers here you need to pick.

So this is B and C.

Malignant tumours invade healthy tissue, and they can enter the blood and the lymphatic system.

A is incorrect.

Malignant tumours are not contained within a membrane.

Benign tumours are contained within a membrane.

We are now ready to move on to task B of the lesson.

And in the first part of task B, you need to label and annotate the diagrams to explain the difference between benign and malignant tumours, and you need to identify which one is which.

There are labels on there to help you.

And then in the second part of task B, you need to use the diagrams and the words below to help explain why malignant tumours are dangerous.

So there's two diagrams here, and the words you need to use are invade, healthy, function, blood, lymphatic, and spread.

So give this your absolute best go, and then press play when you're ready for me to go through the answers.

Let's see how we did.

So the diagram on the left hand side is showing you a benign tumour, and that's a growth of abnormal cells that divide uncontrollably.

And then you can see surrounding that benign tumour there is a membrane.

And then also you've got neighbouring tissue which is not invaded.

Those are healthy cells as well.

You might have written that in, but the idea that the neighbouring tissue is not invaded is really important.

And then on the right-hand side we've got the malignant tumour, which is a growth of abnormal cells that divide uncontrollably again, but key difference here is that the neighbouring tissue is invaded as the tumour is not held within a membrane.

And then that circled cell at the top there is showing you a malignant cell that's broken off and can spread to form secondary tumours, and this is called metastasis.

Fantastic job if you manage to get those down.

Well done.

Let's move on to the second part.

So these two pictures are split up over two slides here.

So in the first picture, this is showing you that malignant tumours invade healthy neighbouring cells.

In the lungs, the tumour cells invade healthy lung tissue to form more tumours, and this affects the function of the lungs.

You might not have that exactly word for word, but just maybe pause the video and check that you've got the main key points in your answer.

And in the second picture, this has shown you that malignant tumour cells can enter the blood and the lymphatic system, and this means that they are able to easily spread around the body.

You might have also written here that this can form secondary tumours and cause the cancer to spread.

Amazing job so far.

Well done.

We're ready now to move on to the third and final parts of our lesson.

So we know what cancer and cell division is.

We know the difference between benign and malignant tumours.

So let's move on to the final part of our lesson, which is risk factors for cancer.

Anyone can develop cancer, but there are certain risk factors that increase the chances of developing the disease.

Being exposed to a risk factor does not mean you would definitely get it.

So it's important to identify here that a risk factor is just something that increases the chances of developing something.

It doesn't mean you're definitely going to get that disease.

Can you recognise any of the risk factors associated with cancer, looking at these pictures? Let's see if you could identify any of them.

So the first risk factor is smoking.

The second risk factor is obesity.

The third risk factor is UV radiation.

And the fourth risk factor is viral infections.

There are other risk factors as well, but these are the main ones that you need to know about.

All four of these risk factors are called lifestyle risk factors, and we'll come onto how some viral infections are to do with lifestyle.

But there is another type of risk factor, which is genetic risk factors.

These are not something that somebody can choose to do.

You would be born with certain inherited genes that increase your chances of developing cancer.

The table below shows how lifestyle risk factors are linked to the development of different types of cancer.

So we're going to start first of all by looking at the risk factor smoking, which is in the top of the table.

And there are different types of cancer that smoking is linked to.

The main one is lung cancer, but also smoking is linked to mouth, bowel, stomach, and cervical cancer.

Obesity is linked to bowel, liver, and kidney cancer.

UV exposure is linked to skin cancer.

And viral infection, there are two different types of viral infection.

The first one is HPV, and that is linked to cervical cancer, and then hepatitis B and C are linked to liver cancer.

Look at Smoking in a little bit more detail.

So smoking contains chemicals that are carcinogenic.

Carcinogenic means cancer-causing.

An example is tar.

So tar is found in cigarettes, and tar is known to be carcinogenic.

And because you are breathing in or inhaling the carcinogenic chemicals, the one organ in particular that's really affected are your lungs.

So smoking is quite heavily linked with lung cancer.

Then the second risk factor is obesity.

Obesity is associated with an increased risk of developing bowel, liver, and kidney cancer.

Unhealthy diets high in fat and salt, and drinking excessive amounts of alcohol are associated with an increased risk of developing cancer.

UV exposure can be increased in the following ways, living in a sunny climate, spending lots of time outdoors, and using sunbeds.

UV is ultraviolet light, and it is a type of radiation that is emitted by the sun.

So if we're talking about spending time in the sun, how can that risk be reduced? Well, you could spend less time in the sun.

And if you are in the sun, you need to wear sun cream.

In terms of using sun beds, so sun beds expose users to UV radiation.

How could you reduce that risk? Well, just don't use sunbeds.

The reason why UV exposure is linked to lifestyle is because there are choices that we can make that will either increase or decrease our UV radiation exposure.

Viral infections such as hepatitis B and C can be spread through unprotected sex and sharing needles.

And remember that hepatitis B and C are linked to liver cancer.

The reason then why this is linked to lifestyle choice is because people may choose to have unprotected sex and share needles.

That's not always the case, but some people choose that as part of their lifestyle and therefore they are increasing their risk of developing liver cancer.

In the same way that HPV can be spread through unprotected sex, HPV is linked to cervical cancer.

Now, it's not always the case, but some people make a choice as part of their lifestyle to have unprotected sex, so therefore they are increasing their risk of developing HPV and therefore cervical cancer.

Let's do a quick check for understanding.

So your job here is to match the type of cancer with its associated risk factor.

You have a go now.

So the first one is linked to viral infection, skin cancer is linked to UV exposure, bowel cancer is linked to obesity, and lung cancer is linked to smoking.

Great job if you got that right.

Next question.

Which of the following would help to reduce the risk of skin cancer? A, do not use sunbeds, B, wear sunscreen, or C, spend more time in the sun.

This is A, do not use suns and B, wear sunscreen.

If you spend more time in the sun, you're actually increasing your UV exposure.

So far we've looked at risk factors linked to lifestyle.

Risk factors for cancer can also be associated with genetics.

You can inherit faulty genes that make you more susceptible to cancer.

And this is not a lifestyle choice because you are inheriting those genes, and there is no choice involved.

One example of inheriting faulty genes is the BRCA mutations.

So there's BRCA1 and BRCA2.

So mutated BRCA genes have been linked to an increased likelihood of developing breast and ovarian cancer.

BRCA genes are tumour suppressor genes that help to prevent uncontrolled cell division and repair damaged DNA.

So healthy normal BRCA genes will actually prevent uncontrolled cell division from occurring.

They are tumour suppressor genes.

So here we've got an image of a BRCA gene, and the BRCA genes usually help to control the cell cycle.

So if that's a cell cycle, the BRCA gene normally helps to maintain that controlled cell division and healthy tissue.

A faulty BRCA gene or a mutated BRCA gene means these genes do not work properly and cell division can become uncontrolled, increasing the risk of cancer.

Let's check our understanding.

So first question, risk factors for cancer are linked to, A, lifestyle, B, genetics, or C, lifestyle and genetics.

This is, C, lifestyle and genetics.

Well done if you remembered that.

Next question, which gene is linked to breast and ovarian cancer? A, RABC, B, BRCA, or C, LCDA.

This is B, the BRCA gene, which we call the BRCA gene.

Fantastic if you remember that.

We're now ready to move on to the final task of the lesson, task C, and your job is to use the images to identify the risk factor for cancer and which cancer it is linked to.

So we've got two images here, and then we've got question three and four here with some images.

And then finally, in question five, Laura and Izzy are talking about risk factors for cancer.

Who is correct? Explain why, giving examples.

So Laura has said, "Risk factors are only caused by lifestyle." And Izzy has said, "Risk factors can be caused by lifestyle or genes." I'm sure you're gonna do a great job.

Pause the video and then press play when you're ready for me to go through the answers.

So let's look at the first part of task C.

So the first image is smoking is a risk factor for cancer.

It has been linked to lung, mouth, bowel, stomach, and cervical cancer.

And then number two is obesity is a risk factor for cancer.

It has been linked to bowel, liver, and kidney cancer.

So well done if you got those right.

Part three, this is showing you how exposure to UV radiation is a risk factor for skin cancer.

Living in sunny climates, spending too much time in the sun, or using some beds can increase the risk.

And then finally, number four is showing you that certain viruses are linked to cancer, and HPV is linked to cervical cancer and is spread through unprotected sex.

And hepatitis B and C are linked to liver cancer and are spread through unprotected sex and needle sharing.

So great job if you manage to get all of that information in.

And then for question five, Izzy is correct because risk factors can be caused by lifestyle and genes.

Smoking, obesity, UV exposure, and viral infections are all linked to lifestyle.

However, there are certain genes you can inherit that increase your chances of developing cancer, and then it is that the BRCA genes, what we talked about, are associated with an increased risk of developing breast and ovarian cancer.

BRCA genes are tumour suppressors that usually control the cell cycle if they are faulty, and cell division can become uncontrolled, leading to cancer.

There's quite a lot of information there.

So if you need to pause the video and go back to check anything, then please do.

We're going to summarise the lesson in the next slide.

So today's lesson was called "Errors in Cell Division and Cancer: The Basics." And we started off by saying that mitosis forms part of the cell cycle, and that the cell cycle is regulated by genes.

And we said that genes were short sections of DNA.

Cancer is caused by changes in the cell DNA that leads to uncontrollable cell division.

So some cells have their DNA changed, and that can lead to uncontrolled cell division.

And we said then that tumours are masses of cells formed from uncontrolled cell division, and that they can be either benign or malignant.

Benign tumours are contained within a membrane and cannot invade neighbouring tissue.

They are non-cancerous.

Malignant tumours invade neighbouring tissue and can spread to other parts of the body.

They are cancerous.

Then the final part of the lesson, we spoke about risk factors, and we said smoking, obesity, UV exposure, and viral infections are lifestyle risk factors linked to cancer.

And then we said that certain genes are also risk factors for developing cancer.

For example, the BRCA genes.

You've done really well today.

I've really enjoyed today's lesson and I hope you have too.

I look forward to seeing you next time.