Welcome to this lesson for the Oak National Academy.

Today's lesson is called "Variation and Genetic Mutations", and it's taken from the unit, "Variation and Natural selection At The Genetic Level".

Hiya, I'm Mrs. Wheate and I'm gonna be your teacher for today's lesson.

By the end of today's lesson, you'll be able to describe how mutations change the DNA sequence in the genome causing genetic variation, which can cause heritable variation in phenotype.

Let's have a look at our keyword.

Today's lesson has got five keywords.

Phenotype, the observable traits of an organism.

Variation, differences between members of the same species.

DNA, a large chemical molecule made of nucleotides.

It carries the genetic codes of all living organisms. Mutation, a change in the nucleotide base sequence in the DNA of the genome.

And genetic variant, a region of DNA in which the sequence of nucleotide bases has been changed.

So if you wanna read through that again, I'll be quiet for five seconds so you can do that, but if you want a longer period of time maybe to read through those a couple of times or to copy it down, click pause and click play when you're ready to move on with the lesson.

Today's lesson is in two parts.

First of all, we'll talk about variation and phenotype and in the second part of today's lesson, we'll talk about mutations and genetic variation.

But first of all, variation and phenotype.

The observable traits an organism has are known as its phenotype.

So your eye colour is a part of your phenotype.

Your phenotype could also be whether you're left-handed or right-handed, what your hair colour is, how tall you are, all of the characteristics that make you who you are.

So the differences in phenotype that we have between members of the same species is known as variation and variation in phenotype, so changes in phenotype like so the person there has got brown eyes, that's variation in phenotype from the person that's got like bluey-green eyes.

So that variation in phenotype is caused by two main factors.

It could be caused by a environment or lifestyle, we put those in a similar category.

Or it could be caused by our genetic information.

So we'll start with variation caused by environment.

So variation caused by the environment is known as environmental variation.

So the environment is the surroundings of an individual organism and that includes things like the temperature, sunlight availability, pollutants, availability of nutrients and soil pH.

Pretty important if you're a plant.

So examples and changes in phenotype that's caused by environmental variation include, so temperature of eggs controls sex for many crocodile species.

Isn't that fascinating that the temperature of the egg decides whether it's gonna be a batch of male or batch of a female? Fascinating.

Exposure, so a human example, exposure to sun can cause freckles.

That's another example of changes in phenotype caused by environmental variation.

So some variation is caused by your lifestyle.

So the lifestyle of a person is the things that they do and the choices they make, such as diet, exercise and modifying their bodies.

So an example here, we've got a scar that could be caused by damage.

We've got a body piercing, which was a choice that person made, and this person is exercising.

So again, that's part of their lifestyle, something they're choosing to do to their body.

Variation caused by environment or lifestyle cannot be inherited.

So we've got a photo of a father and a son here.

So can you look at this photo and can you tell me what is something that the father has that cannot be inherited by the son? So that's gonna be something that's part of the father's environment or lifestyle, so a choice he made or something that happened to him in his environment.

You can take five seconds or pause the video if you want more time, click play when you're ready to see the answer.

Okay, something that wasn't passed from the father to the son, so you could've said tattoos.

So dad's got tattoos, son doesn't have tattoos.

That's not something that's inherit from your parents.

You can choose to get tattoos when you're older, but that's not necessarily anything to do with your parents.

You could've also said piercing.

There's probably other examples that I couldn't see, but that kind of thing.

Anything caused by environment or caused by lifestyle.

Right, not all variation however is caused by the environment or lifestyle.

So some variation is caused by an organism's genetic material.

This is known as genetic variation.

So genetic variation is heritable.

It is caused by our DNA, so our genetic material, and can be passed on from parent to offspring through reproduction.

So not like tattoos, not like ear piercings, this is something that's in our DNA.

So this can be through sexual reproduction which involves the fusion of male and female gametes, so sex cells.

The male gamete in animals and plants being called sperm and the female gamete being called an egg cell.

So in this example, so some plants produce flowers and that allows them to sexually reproduce and through that sexual reproduction, traits will be passed on from the parent plant to the offspring.

So genetic variation can also be inherited through asexual reproduction, which is a form of reproduction that uses cell division and makes genetic identical offspring.

So some plants, this is a spider plant, this is my spider plant actually, so some plants reproduce asexually and that makes genetically identical clones of themselves.

So anything that this parent spider plant has is being passed on to the little offspring spider plant.

On the end of that, that horizontal stem which is called a runner.

Bacteria also reproduce asexually by dividing to make two genetically identical cells.

So whatever the parent, not really parents in this aspect, but go with me with the analogy.

So you've got the parent bacteria, divides into two and creates two genetically identical cells or like the offspring bacteria.

Okay, let's see if you understood that.

Which of the following statements is true? A, variation caused by the environment is heritable.

B, variation caused by genetic material is heritable.

C, variation caused by the environment and genetic material is heritable.

D, variation occurs randomly and is not influenced by the environment or genetic material.

Take five seconds to think about your answer or if you want more thinking time, click pause, click play when you're ready to see the answer.

Okay, the correct answer is B, variation caused by genetic material is heritable.

Well done if you got that right.

So let's look at some examples of changes in phenotype caused by genetic variation.

So the markings on a butterfly's wings, that's caused by genetic variation.

So it's passed on from parent butterflies to the offspring of the butterfly.

And the blood type you have.

That's caused by your genetic material.

So your blood type will be similar to your parents' or a combination of your parents' blood types.

So most changes in phenotype are caused by a combination of genetic and environmental and lifestyle factors.

I had to very, very selective to pick some examples that were just purely caused by environment and just purely caused by genetics.

In reality, it's a combination most of the time.

So for example, our body mass is partly controlled by our genes, it's also influence by our lifestyle.

It's depending on what we eat and how active we are, our body mass will change.

Okay, let's check to see if we understood that.

True or false.

Genetic variation is inherited through sexual reproduction only.

Is that true or is that false? Take five seconds or pause the video if you want more time, click play when you're ready to see the answer.

Okay, that is false.

Okay, why is it false? Let's justify our answer.

It's false because genetic variation is inherited through asexual reproduction only or genetic variation is inherited through asexual and sexual reproduction.

Take another five seconds or pause the video if you want some more time to think.

It is B, genetic variation is inherited through asexual and sexual reproduction.

Well done if you got that right.

This is the first practise task of today's lesson.

Answer the questions and complete the tasks below.

Number one, define the term phenotype.

Number two, define the term variation.

Number three, state the two types of variation.

Number four, state how genetic variation can be passed on from parent to offspring.

So you need to pause the video now to give yourself enough time to complete your answers.

Click play when you're ready to see the answers.

Okay, let's go through the answers.

Number one, define the term phenotype.

Phenotype is an organism's observable traits.

Number two, define the term variation.

Variation is the differences between individuals of the same species.

Number three, state the two types of variation.

Environmental variation and genetic variation.

Number four, state how genetic variation can be passed on from parent to offspring.

Genetic variation can be passed on from parent to offspring via sexual or asexual reproduction.

Great job if you got that right.

Okay, let's have a go at the next few questions.

The following features are a part of this woman's phenotype.

Spanish accent, tattoos, dyes red hair, blood type, natural eye colour.

For each feature, state whether it is caused by environmental or genetic factors and number six, she is expecting a baby, which of the features could be passed on to her child? Explain your answer.

So again, you need to pause the video now to have enough time to do your answers, click play when you're ready to see the answers.

Okay, let's check to see how you did.

So Spanish accent, that is cause the environment.

Tattoos, environment or lifestyle you could say.

Dyed red hair, environment or lifestyle.

Blood type, that's genetic.

Natural eye colour, that's genetic.

Number six, she is expecting a baby, which of these features could be passed on to her child? Explain your answer.

Her blood type and natural eye colour could be passed on to the baby as these are caused by genetic variation.

The other features are all caused by environmental variation so will not be passed on, because environmental variation is not heritable.

Really good job if you got those right.

We have completed the first part of today's lesson.

We have looked at variation and phenotype and the relationship between them.

Now we're gonna look at mutations and genetic variation.

DNA is a chemical molecule and it stores the genetic code for all living organisms. So a bit of a reminder.

So here we've got a cell and inside the nucleus of a cell, we've got chromosomes and those chromosomes are made up of DNA.

So genetic variation could be caused by changes in DNA known as mutations.

We're gonna look at the structure of DNA and that will help us understand what a mutation is.

So DNA is long chemical molecule.

Something really weird about DNA is that it's somehow incredibly big and incredibly tiny at the same time.

It's really, really, really long, but it can fold small enough to fit inside the nucleus of every single one of your cells.

DNA is a polymer and that means it's a big molecule that's made up of short repeating units.

These short repeating units in DNA are known as nucleotides.

Let's have a closer look at some of the nucleotides.

So here we have three nucleotides and this section here is just one nucleotide and we've also got bonds holding these nucleotides together.

A nucleotide has three parts.

It has a sugar, it has a phosphate and we have a base.

So there are four based that it could be, adenine, thymine, cytosine or guanine.

We abbreviate those to A, T, C and G.

So base it could be an A, it could be a T, it could be a C or it could be a G.

And we'll talk about those bases in more detail, but for now, let's check to see if you're following with me.

Label the following structures.

So take five seconds or pause the video if you want more time.

Click play when you're ready to see the answer.

Okay, let's check our answers.

A, that's a cell.

B, that's a nucleus.

C, DNA and D, that's base.

Great job if you got that right.

The genetic code is determined by the order of the bases on the nucleotides and these are stored in the middle of the DNA double helix structure.

So where is that on this diagram? So again, here we've got a section.

We've got DNA is a two-stranded molecule, so two strands that are twisted around each other into a helix.

We've kind of unravelled that and zoomed in on the diagram that I've just added.

And that small section there, that's a nucleotide.

And the order of those bases, that creates the bases of our genetic code.

Let's talk about the genetic code in more detail.

The genetic code, stored in sections of DNA called genes, is read in groups of three.

This is called the triplet code.

Each triplet codes for a specific single amino acid used to make a protein and therefore, the order of the nucleotide bases is important.

So here we have a section of DNA.

It's six nucleotides long, so that means it's gonna code for two amino acids.

The first three nucleotides here, the bases CAG are gonna code for a specific amino acid and the next three bases there, the TCA, they're gonna code for another amino acid.

And those amino acids will bond together to form a protein.

Okay, let's check to see if you understood that.

How many amino acids can be made from this DNA sequence? Take five seconds or pause the video, click play when you're ready to see the answer.

Okay, the answer is four amino acids.

Let's see why, so if we divide this chain into threes.

And remember that the triplet code is three nucleotides.

We've got 12 nucleotides in total, so makes four different amino acids.

Well done if you got that right.

Okay, now we talked about the structure of DNA, we can start talking about mutations and genetic variation.

So mutations are changes in the nucleotide base sequence.

This change creates something called a genetic variant.

A genetic variant is a region of DNA in which the sequence of nucleotide bases has been changed.

So that's quite abstract, let's make that a bit more visual.

So here have on the top here, I've got one strand of DNA.

I'm just gonna talk about one strand, I'm aware it's double-stranded, but just looking at one makes it a lot easier.

And underneath we have a genetic variant.

Can you see the differences between those different strands of DNA? So take five seconds or pause the video if you want some more time.

Click play when you're ready to see the answer.

Okay, did you find the difference? It is here.

So on our original sequence of DNA, this is like the un-mutated strand of DNA, the base there is an A.

In the strand of DNA that has a mutation in it, the genetic variant, that base has been changed to a C.

So mutations happen at random.

They can also be caused by carcinogens, such as the carcinogens in tobacco smoke or ionising radiation such as UV light from the sun or X-rays.

Mutations could also be caused by naturally occurring mistakes when DNA is copied during cell division.

So the vast majority of mutations have no effect on an individual's phenotype.

We hear the word mutation and it's a bit scary.

We think it's maybe something to do with radiation, but the vast majority of mutations are benign, they don't have really any effect at all.

So one reason for this is that the several different triplet base codes can code for the same amino acid.

So if we look at this example.

So I've got an original sequence in DNA and I've got my sequence which is genetic variant that contains the mutation.

If we look at the third base along, that's changed due to maybe some interaction with ionising radiation or maybe a carcinogen in alcohol or in cigarette smoke, however, in this case, so GAA, the triplet code GAA and the triplet code GAG, they code for the same amino acid, so the mutation has no effect.

So that's one reason why a lot of mutations don't have any effect on our phenotype.

So sometimes mutations in genes do affect our phenotype.

Let's look at another example.

We got our original sequence in DNA, we've got our genetic variant sequence.

So here we have a change to the second base.

So instead of an A, it's a T in the genetic variant example.

So some mutations create base triplets that code for different amino acids, which can change the protein that is synthesised and cause differences in phenotype.

So in this example, the triplet code GAA codes for one amino acid and the triplet code GTA, that codes for a different amino acid.

They then will bond together differently and potentially create a protein that has a different shape and has a different function, leading to a different phenotype.

So where a mutation changes a protein that is made, this can influence a trait such as hair colour or texture, which will also be influenced by environment and lifestyle or it can determine a trait such as a blood type.

This isn't influenced by environment or lifestyle at all, this is purely controlled by genetic factors.

Okay, let's see if we understood that.

True or false, mutations always lead to changes in phenotype.

Is that true or is that false? Take five seconds or pause the video if you want more time.

Click play when you're ready to see the answer.

Okay, that is false.

Let's justify the answer.

Why is it false? It false because only environmental variation can lead to changes in phenotype or B, when mutations change the protein that is made, they can also affect phenotype? Take five seconds or click pause if you want more thinking time.

Click play when you're ready to see the answer.

Okay, the answer is B, when mutations change the protein that is made, they can affect phenotype.

Great job if you got that right.

This is the final practise task of today's lesson.

Number one, define the term mutation.

Number two, define the term genetic variant.

Number three, state three things that can cause mutations in DNA.

Number four, look at the base sequence below.

A, how many amino acids does it code for? Explain your answer.

B, describe the possible effects of changing the third base to an A.

So you'll need to pause the video now to give yourself enough time to do those answers.

Click play when you're ready to see the correct answers.

Okay, let's go through the answers.

Number one, define the term mutation.

A mutation is a change in the nucleotide base sequence in the DNA of the genome.

Number two, define the term genetic variant.

A genetic variant is a region of DNA in which the sequence of nucleotide bases has been changed.

Number three, state three things that can cause mutations in DNA.

So you could've written carcinogens, ionising radiation, so like UV, X-rays or gamma rays.

You couldn't have written UV, X-rays and gamma rays as your answer, those are all ionising radiation.

They're too similar to be separate answers.

And you could also have written, mistakes during DNA replication.

Okay, question four.

How many amino acids does it code for? Explain your answer.

It codes for three amino acids.

This is because there are 11 nucleotides in total and three nucleotides are needed to code for one amino acid.

So that's the triplet code.

Suggest the possible effects of changing the third base to an A.

So it could have no effect.

This is because the new base sequence could code for the same amino acids as there is more than one triplet code for each amino acid.

Or it could lead to a different phenotype.

If the new base sequence codes for a different amino acid, this could lead to a new protein being formed which could lead to a difference in phenotype.

Great job if you got those right.

Well done on your hard work in today's lesson.

Let's summarise what we've learned to help it stick in our memories.

The observable traits of an organism are known are its phenotype.

Some variation in phenotype is caused by the environment or by lifestyle and is not heritable.

Some variation is caused by differences in genetic material and can be passed to offspring during sexual or asexual reproduction.

Genetic variation can be caused by mutations, which are changes in the nucleotide base sequence in an organism's DNA.

Mutations happen at random and can be caused by carcinogens, ionising radiation or by errors when DNA is copied.

They can create a different version of a gene called a genetic variant.

Some mutations affect phenotype by changing proteins that are made, but most mutations do not have any effect on phenotype.

Again, well done on today's lesson.

I hope you really enjoyed it and see you again soon for our next lesson.