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Y9 Genetics - KS3 Science

Fertilisation - Variation & its causes - Genes & Inheritance - Selective Breeding - Cloning

J Amuah-Fuster

on 8 July 2016

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Transcript of Y9 Genetics - KS3 Science

Genetic Diagrams
Define what a chromosome is and explain where they can be found.

State which chromosomes are responsible for sex inheritance.

Explain how sex is inherited

Identify characteristics in animals and plants that might be desirable.

Explain how selective breeding in animals and plants results in offspring with desirable features.

Describe the arguments for and against using selectively bred chickens.

Evaluate evidence and different viewpoints to form your own opinion.

Define the term ‘clone’.

Describe how to clone an animal.

Explain some of the advantages and disadvantages of cloning animals.

Describe how sexual reproduction results in genetic information being inherited from both parents.

Describe similarities and differences in fertilisation in plants and animals.

Explain how identical and non-identical twins are formed.

Identify a range of characteristics in plants and animals that are inherited.

Identify some features in plants and animals that might be affected by the environment.

Describe the difference between continuous and discontinuous variation.

Genes & Inheritance
Selective breeding in animals - Is it OK?
Causes of Variation
What are chromosomes?
Is it a boy or a girl?
How gender is inherited
We often show discontinuous variation on a bar chart.

Discontinuous & Continuous Variation
Describe how we inherit characteristics.

Explain what dominant and recessive versions of genes are.

Draw genetic diagrams to show inheritance of particular characteristics.

The next generation
6. Put a polythene bag over the flower
to protect the stigma of Flower B
How do we selectively breed?
What is selective breeding?
What is a clone?
How to clone a sheep
What do you remember?

Human Fertilisation video clip
Journey of a Sperm
What’s the female gamete in humans?
And in flowering plants?
The sperm is the male gamete in humans.
What’s the male gamete in flowering plants?
The sex cells, or gametes, combine at fertilisation.
Like animals, plants pass on their genetic information when they reproduce.
Plant sex!
For the gametes to fuse at fertilisation, the pollen must find the egg cell.

What carries the pollen from each of the flowers shown below? How can you tell?

Wind or insects carry pollen from one flower to another for pollination.

The seed that grows contains genes from both the pollen grain and the egg cell.

The pollen nucleus reaches the egg cell. They fuse – fertilisation.
The pollen tube reaches the ovule, carrying the pollen nucleus.
A pollen tube grows down the style from the pollen grain.
How do the gametes fuse to combine the genes in flowering plants?
Pollination: –
the pollen arrives at the stigma.

egg cell




Fertilisation in flowering plants
flowering plants


Egg cell
Sexual intercourse
Egg cell
Fertilised egg grows to form a…

Gametes fuse during

Male gamete transferred by

Female gamete

Male gamete

The nuclei of the gametes carry genetic information.
The new life has genetic information from both parents.
Fill in the boxes for humans and flowering plants.
Plant and animal sex...
Sex is really the same thing in plants and animals.
Non-Identical Twins
50% of their genetic information is the same (like brother and sister).
Identical Twins
100% of their genetic information is the same.
Fill in the blanks…
Born on Christmas Eve, 1909 – how old are they?
What similarities are there between them?
What differences are there between them?
Meet the oldest living identical twins in the world…
Some characteristics are controlled only by genes we inherit from our parents e.g. gender or blood group.
BOTH inherited and environmental
These plants are all the same species. How do they vary from one another?
Plant Variation
The environment can affect plants too.

Bonsai trees are miniature trees.
They have the normal genes for tallness but are small because they have been grown in small pots.
Plant variation
3. What’s your foot length?
2. What’s your shoe size?
1. Can you roll your tongue?
Investigating variation in our class….
beetle spots

1 2 3 4 5
number of beetles





number of people

blood group

blood group

Can you think of some more examples?

You either do have a J in your first name, or you don’t. (You can’t have half a J!)

In discontinuous variation, all the possibilities fit into neat classes – ‘yes’ or ‘no’; ‘2 spots’ or ‘3 spots’.
What is discontinuous variation?
184cm 172cm 169cm 166cm 177cm 175cm
And the winner this year is … Doris, who is 175 cm tall and has four lovely grandchildren.
Every year they have a glamorous granny competition at this holiday camp.

Continuous Variation
few tall people

lots of middle-sized people

few short people

height (cm)




heights of glamorous grannies

number of people




hand span (cm)

hand spans of 9X

Suggest some more examples of continuous variation.

The grannies had a range of heights. We use a line graph to show continuous variation.

In continuous variation, there is a range of possible results. We usually have to measure something.

Continuous variation
Some are controlled by the environment e.g. sun tan or having a scar
hair colour, eye colour, hair length, shoe size, memory, accent,

having pierced ears, weight, height, skin colour, sporting ability,

nail length, ear lobe length, having a scar
Sort these characteristics into 3 groups:
number of spots
number of people
How will you record and present the observed data?



skin colour

large ear lobes

mass at age 21

mass at birth

scar on left knee

can run very fast


blood group A

green eyes

Chromosomes, Genes and DNA
Cut out the chromosomes to match up the 23 pairs
What happens to chromosomes in fertilisation video clip

Every one of our body cells contain ….. chromosomes arranged in …. pairs.
They come in pairs because……….
The sex cells (….. and …… cells) contain half the normal number of chromosomes (….. single chromosomes).
One pair of chromosomes control your gender ( the … and … chromosomes)
Chromosomes and Inheritance

The colour of your eyes is a characteristic that is inherited.
You inherit characteristics from your mother only.
Your brothers or sisters inherit exactly the same characteristics as you.
All animals inherit some characteristics from their parents.
Plants are not able to inherit characteristics.
The environment has no effect on your characteristics.
Chromosomes carry genetic information and are found inside every cell.
There are half as many chromosomes in sex cells (gametes) as there are in normal body cells.
Fertilisation is when a sperm cell fuses with an egg cell.
A fertilised egg cell only contains half the genetic information of a normal body cell.
True or False?
Sex Inheritance Animation
Male or Female?



Sex inheritance video clip
If identical twin brothers married identical twin sisters, would all their children look the same?
The children have an equal chance of looking the same or different
The children would have some similarities but still differ
All the children would look completely unalike from each other
Who do you agree with?
Marge has curly hair
Homer has straight hair
The parents
Is hair curliness controlled by genes or by the environment?
The families
Homer has straight hair.

Every cell in Homer has two sets of chromosomes. Pair 17 controls hair type.

Both of Homer’s chromosomes carry a straight hair version of the hair type gene.

We can show the straight hair version of the hair type gene with a capital H.

Homer’s genes: HH.
Marge has curly hair.

Every cell in Marge has two sets of chromosomes. Pair 17 controls hair type.

Both of Marge’s chromosomes carry a curly hair version of the hair type gene.

We can show the curly hair version of the hair type gene with a small h.

Marge’s genes: hh.
Homer makes sperm
Each sperm has one copy of the gene for hair type.

Homer only has straight hair genes.

So all of his sperm have straight hair genes

Homer’s Sperm
Making a new Simpson

Marge makes eggs
Each egg has one copy of the gene for hair type .

Marge only has curly hair genes.

So all of her eggs have curly hair genes

Marge’s Eggs
Making a new Simpson
All of the Simpson babies have one gene for curly hair and one gene for straight hair
So what type of hair do they have….?
Making a new Simpson
The straight hair version (H) of the hair type gene is DOMINANT
Just one copy of this gene will give you that characteristic
The curly hair version of the gene (h) is RECESSIVE
You need two copies of the gene to have that characteristic
Making a new Simpson
Which version of the gene is dominant?
Can the Simpson children roll their tongues?
Extra Practice

Lisa has straight hair.

Every cell in Lisa’s body has one copy of the gene for straight hair, which is dominant.

Every cell also has one copy of the gene for curly hair, which is recessive.

Lisa’s genes: Hh
The next generation?
Milhouse has straight hair.

Every cell in Milhouse has one copy of the gene for straight hair, which is dominant.

Every cell in Millhouse also has one copy of the gene for curly hair, which is recessive.

Milhouse’s genes: Hh
Straight hair is
What percentage of their children would have straight hair?
What percentage would have curly hair?
The next generation?
The children would have some similarities but still differ
R (red) is dominant over r (white) for eye colour
Which colour will be the most common?

Follow the instructions in Spotlight Science 9 pg127
Work out the different amounts (ratio) of offspring that will be born
Complete the table.
Answer qus gj

Extension qus 2, 3 pg 127
Take a chance practical
All the children would look identical
Homer can roll his tongue.

Every cell in his body has two copies of the tongue rolling version of the gene.

His genes are: RR

Homer’s sperm
Tongue Rolling
Marge cannot roll her tongue.

Every cell in her body has two copies of the non-tongue rolling version of the gene.

Her genes are: rr

Marge’s Eggs
Tongue Rolling
Making a new Simpson
1. Can you roll your tongue?
The next generation?
The next generation?
Zoo Selective Breeding Game – click hyperlink!
For example, apple growers want to produce a type of apple that is tasty and resistant to disease.

This can be done by crossing a variety of apple known for taste with another variety that shows strong resistance to disease.
Selective Breeding
However she has decided that she would like her future child to have:

Blue eyes
Blonde Hair
Be tall (over 6ft)

How can she increase her chances of achieving this?
Single Jackie is looking for love….
Racing pigeons

Race horses

Dairy cows
Examples of selective breeding
Very large fruited child!

Large fruited Mum

Large fruited Dad

Selective breeding is a process used to produce different breeds of animals or varieties of plants that have useful or desirable characteristics.

Using selective breeding you can produce offspring with desirable characteristics of both parents.
Selective Breeding
6. Plants can survive with little water.

7. Strawberries rot quickly

12. Plants have small leaves

11. Small strawberries

10. strawberries are very tasty

5. strawberries are juicy

9. Plants are resistant to disease

8. strawberries stay fresh for a week after picking

4. strawberries are bright red

3. Plants produce lots of strawberries

2. Big strawberries

1. Plants will not die in temperatures below 4ºC

Your task is to write an article for Plant Growers Weekly about using selective breeding to grow better plants.

You need to explain:
Why a plant grower should use selective breeding and
How they can carry it out

1. A farmer who grows tomatoes to sell to supermarkets
2. A person who grows prize-winning tulips to enter shows
Sometimes breeding between close relatives makes genetic deformities more frequent.
British Bulldogs for example have such large heads that they are unable to be born without Caesarean Section. They are prone to breathing difficulties and heart problems.
Other dog breeds are prone to diseases such as cancer and arthritis.
Is it all good news?
Breeding Plants
5. Rub the pollen over the stigma of Flower B
Breeding Plants
4. Rub a brush over the anthers of flower A.
Breeding Plants
Breeding Plants
So it is not pollinated by other pollen
Breeding Plants
To ensure that flower B is not fertilised by its own pollen.
3. Remove the anthers.
To get the best strawberries (large and tasty) the farmer must breed together the best two offspring, and keep repeating this over and over until he gets the perfect strawberry.
If he breeds the two plants together then the offspring will have a variety of their parent’s characteristics.
Breeding Plants
Breeding Plants
2. Flower A will produce the pollen and Flower B
will receive the pollen in its stigma
Variety B grows large but tasteless strawberries.
Variety A grows small but very tasty strawberries.
1. Choose two plants with desirable characteristics.
Suggest to the farmer what he could do to improve the quality of his strawberries.
Variety B grows large but tasteless strawberries.
Variety A grows small but very tasty strawberries.
A farmer grows two different varieties of strawberry plant.
Breeding Plants
Is selective breeding ok?
Read your character card.

Think about…

How could you summarise their viewpoint?
Do you agree with their viewpoint?
What do you remember about selective breeding?
How could you selectively breed chickens to:

Produce more eggs?
Produce more meat?
Are the issues surrounding the selective breeding of fruit any different to those around the selective breeding of chickens ????

Selective Breeding in Chickens Video
Discuss which characters you...

.....most agree with
....least agree with
Take it in turns to tell the rest of your group about your character.
Learning Outcome…

Evaluate evidence and different viewpoints to form your own opinion
I am for selective breeding because......

Complete one of the following statements
I am against selective breeding because......

Your answer you must include both sides of the argument. You must also back ideas up with facts and give counter arguments.
I can negotiate an outcome
I adjust my attitudes/opinions in light of new evidence
I know when to step forward, and when to take a back seat
I tend to work to a collective goal
I take responsibility for the task
I give ideas that take notice of others’ views
I ask questions to extend others’ thinking (& get clarification)
I ask questions to understand others views
What level are you working at?
I give positive feedback to others
I am aware of my own body language
I can resolve conflict
I can recognise strengths & weaknesses in others
Chickens should be selectively bred - Where I stand
Chickens should continue to be selectively bred

Level 7
Employs a systematic approach in deciding the relative importance of evidence

Level 6
Can use a range of evidence to describe a scientific argument

In your groups sort the cards into different criteria, that will help you make a scientific decision on the issue of selective breeding.

What to think about....

For / Against
Facts / Opinions

What further evidence/information you might need.
Dr Sally Johnson 36 Year old Doctor with two children

How can you put a price on the suffering of animals, surely cheaper food should be the least of our worries.

Our demand for cheap food has caused us to make our farm animals work harder often resulting in serious side effects, how can we carry on allowing this to happen?

A third of meat chickens suffer pain whilst standing and a lot die from heart problems, since their bodies grow too fast for their hearts to keep up with.

Very few selectively bred chickens would survive in the wild

“Artificial Selection is just another name for selective breeding. In the wild, natural selection weeds out animals which are not adapted to their environment.

Artificial selection may be useful to us, but it may produce animals which are more likely to suffer.

Why continue doing something that results in the suffering of innocent animals. The bodies of chickens grown for their meat grow too fast for their legs making them unable to walk, which I think is cruel”

Farmer Giles Fields Farms Selectively Bred Chickens

I can produce a lot of eggs and a lot of chicken meat using selectively bred chickens, if I was banned, how would I make a living out of farming?

People have been selectively breeding animals for 1000’s of years, why should I stop doing it now.

The human population is increasing at a unsustainable rate, selective breeding of animals will help feed the World.

Chickens selectively bred for meat can grow twice as quickly as regular chickens

A wild jungle chicken might only lay 20-30eggs a year, my selectively bred chickens lay over 300 a year

“Look, I keep selectively bred chickens sure I understand peoples concerns, I’m not breaking any laws, and I don’t see anything wrong with it.

I think they’ve got a reasonable life. They’ve got the constant company of each other, and food and water on tap.

Supermarkets pay me to produce cheap eggs and chicken meat that’s what the customer wants, So that’s what I do.”

Steven Walker RSPCA Animal Welfare Officer

Why purposely breed animals that could end up with serious health issues?

Everyone has a duty to ensure animals are treated fairly, why do people think selective breeding is any different, animals are suffering, it needs to stop.

2% of selectively bred chickens may end up unable to walk at all.

Each year, in the UK, over 30 million day-old chicks are killed at
birth. These are the males of egg-laying breeds.

“I don’t see how we can turn a blind eye to what goes on. I mean yes, we eat stuff that comes from animals, but we should still look after them properly so they have a good life.

You wouldn't dream of keeping your dog or cat in a cage for most of their lives, so how’s it all right to do that with hens, just because you’re going to eat their eggs.”

Farmer Gary Wilkinson Farms free range chickens

What gives farmers the right to play ‘God’?

Selective breeding means some farmers can rear a chicken in just 42 days, how can I continue to compete with their prices in the market place, whilst maintaining high welfare standards for the chickens?

Eggs and meat from my chickens are healthier for the person eating them.

My chickens grow naturally, unlike the unnatural selectively bred chickens that grow in 50 days

“My chickens are reared to higher welfare standards. They’ve got more space, straw bales to peck at, natural daylight and so on.

They’re a slower-growing breed too. Well, its just good to see them doing what they want to do, and gives me more job satisfaction, to be honest.

At the end of the day, they’re happy, and I'm happy, so everyone’s a winner”

“I have got three children to support, and although I appreciate the issues surrounding selectively bred chickens, I simple can’t afford to buy free range.

Look times are hard, and as long as the food I buy is cheap, I don’t care how it’s produced or what happens to the animals it comes from.

At the end of the day my family comes first, and TV programmes trying to make me feel guilty won’t work. Its just not my problem.

Barry Murphy Manager of Qwick Buy Supermarket

Don’t people have the right to a choice between buying more expensive free range or cheaper non-free range products?

Without selective breeding, the number of chickens and eggs being produced each year would fall dramatically, which would mean a severe price increase on these products

Britain is the one of the largest producers of chickens in Europe, supplying 800 million an year.

1 in 8 people in Britain have low income

“We’re finding more and more customers are asking about farm animals welfare , and choosing higher-welfare products, like those labelled Freedom Food, free-range and organic.

But in these difficult economic times we also have a duty to provide our customers with low-price options, and some people will choose them, and who can blame them.”

Sharon Peters Mother of three – low income family

Why can’t the supermarkets, who make millions of pounds of profit each year, make free range products cheaper?

I need to feed my family and I have a limited budget, buying free range eggs and chicken would mean my children would have to go without elsewhere.

Free range eggs cost £1.69 for six, whereas I can get non-free range eggs for 89p

A free range chicken can cost as much as £4 more than the meat from selectively bred chickens

You can then look at the offspring, choose the individuals with the best taste and most resistance to disease and breed them together.

Repeating this process over many generations results in offspring with the desired characteristics.
Breeding Plants
7. Hopefully fertilisation will happen and a new unique plant is made
Chickens should be selectively bred - Where I stand
Level 7
Level 6
Level 5
Chickens should be selectively bred - Where I stand
Usually we get half our genetic information from each of our parents:
50% + 50% = 100%
What is cloning?
Could produce
In clones, 100% of the genetic information is identical.
Ethics of Cloning
In groups, you are going to make a poster explaining the process of cloning.

Try to include these key terms:
Genetic Material

You also need to include some advantages and disadvantages of cloning.
Your Task
Cloned sheep is born
Nucleus and empty egg cell fuse
Electric Shock
Nucleus removed and discarded
Egg cell removed from donor
Body cell removed from sheep to be cloned
Nucleus removed and kept
Cell division
What are the
missing steps?
Implant into surrogate mother
Remove nucleus from egg cell ...
and throw away
... and another
... and another...
Adult (skin) Cell
Egg cell
Remove some skin cells
Remove nucleus from adult cell...
and keep it!
Place adult cell nucleus inside egg cell
I love my golden sheep!
I wish i could have more just like him.
What about
selective breeding
That takes too long...
I need something
more reliable
How about
adult cell cloning
What's that?
With all
46 chromosomes
within, the egg cell has been
artificially 'fertilised'
When ready, the embryo is
into the uterus of a
The 'fertilised' egg undergoes
cell division
, becoming an
We now have a genetically identical sheep
If we wanted we could create another...
... and another...
Are there any issues with cloning animals?
What about cloning humans?

Full transcript