Download Multicellular Organisms Part 3

Multicellular
Organisms
Part 3
Genetic information
1
Genetic Information Success Criteria
LI To understand the definition of the term species
LI To understand the definition of the term variation and give examples
of continuous and discontinuous variation
LI To understand that characteristics are inherited from our parents
LI To understand that chromosomes are inherited from our parents and
are arranged in matching pairs
LI To understand that we inherit two forms of every gene and these are
called Alleles
LI To understand the definition of the term genotype and phenotype
LI To carry out a simple genetic cross and predict the characteristics of
off-spring
LI To apply my knowledge of genetics and create a “Reebop Baby”
LI To understand how sex is determined by carrying out a simple genetic
cross
LI To identify some of the causes of mutation and give examples of
genetic mutation in plants and animals
2
Genetic Information
The Terms
You will learn the definitions of several important terms as you complete this
topic.
1. To help you remember these create a glossary by copying the following
table in your jotter:
Term
Definition
Species
Variation
Continuous
Variation
Discontinuous
Variation
Gamete
Chromosome
Gene
Allele
Genotype
Phenotype
Homozygous
Heterozygous
True breeding
Mutation
Add information to this table as you complete the topic and learn what these
words mean.
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What is Variation?
LI To understand the definition of the term variation and give examples of
continuous and discontinuous variation
Variation is all the differences that exist between members of the same
species. There are two kinds of variation: continuous and discontinuous.
What to do
1. Draw the table below into your jotter. Then look around the room at your
classmates, note some of the similarities and differences you notice in
the table.
Table – Similarities and differences between the people in my class
Similarities
Differences
1.
1.
2.
2.
3.
3.
4.
4.
Variation Activity (Teacher Led)
What to do
Listen carefully to your teacher. They will explain to you where in the
room you are allowed to move to. When they tell you, move to the area of
the room that you think best describes you for the following
characteristics:







Eye Colour – green, blue, brown, grey
Height
Tongue roller/non-roller
Hair colour – blonde, brunette, black, red
Ear lobes – attached/not
Left/Right handed
Hand span
Discuss with your neighbour: Think back to when you grouped yourselves
according to eye colour, how did this differ to how you grouped yourselves
according to height?
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Continuous variation - type of variation where there is a range of values
(E.g. height or mass)
Discontinuous variation – type of variation where there are clear cut
differences and distinct groups to belong to (e.g. eye colour).
2. Now go back and add the definition for variation, continuous variation
and discontinuous variation into your glossary
What to do
3. Draw this table into your jotter:
Continuous Variation
Discontinuous Variation
1.
1.
2.
2.
3.
3.
4.
4.
5.
5.
4. Add the following examples to your table under the correct heading:










Pulse Rate
Blood groups
Tongue roller/non-roller
Leaf length in grass
Ear lobes attached/not
Hand span
Tail length in dogs
Gender
Flower colour in roses
Stem length in plants
Different types of variation are recorded in different ways:
 Continuous is recorded using a line graph or histogram
 Discontinuous is represented using a bar chart
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5. Find “Continuous variation” diagram in your diagram pack. Using the
What to do
information below, create a histogram by:
(i) Adding a scale to the vertical axis
(ii) Adding a label to the horizontal axis
(iii) Completing the bars
(iv) Drawing a continuous line through the tops of the bars from
start to end
Height of Pupils (cm)
150-154
155-159
160-164
165-169
170-174
175-179
Number of Pupils in
Height Category
3
5
7
6
4
3
6. Describe what happens to the number of pupils in each height category as
the height of the pupil’s increases.
7. Find the “Discontinuous variation” diagram in your diagram pack. Using
What to do
the information below, create a bar chart by:
(i) Adding labels to the horizontal and vertical axis
(ii) Drawing the bars accurately
Eye Colour
Blue
Green
Grey
Brown
Percentage number of
pupils with eye colour (%)
35
25
10
30
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What is Inheritance?
LI To understand that characteristics are inherited from our parents
What to do
1. Collect the “inheritance” card sort from your teacher. Working with your
neighbour, match up the celebrity with their children.
2. Discuss with your neighbour: Why do the children resemble their
parents?
Revision Activity
1. Copy and complete the sentence using the word bank below:
……………………………. carry genetic information and are contained in the ………………
of a cell. They are made of …………….. and are split into sections called
……………….
Word Bank
DNA
genes
chromosomes
nucleus
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What to do
Read the following passage and answer the questions that follow:
Every cell in the human body contains 46 chromosomes. Chromosomes
carry genetic information that control what we will look like.
Children often resemble their parents. This is because they share similar
DNA with their parents. When a sperm (carrying the father’s genetics)
fuses with an egg (carrying the mother’s genetics), the fertilised egg will
contain genetic information from both parents.
The sperm and egg are sex cells, also known as gametes. They are
different from normal body cells because they contain half the number of
chromosomes. A human sperm cell contains 23 chromosomes and a human
egg cell contains 23 chromosomes, when they fuse the fertilised egg
contains 46 chromosomes (or 23 pairs of chromosomes).
Answer the following questions in full sentences:
1. How many chromosomes does a normal human body cell contain?
2. Explain why children resemble their parents.
3. Complete the following note using the information in the passage:
Gamete is another name for a …………… cell. In mammals the male gamete is called
a ………………. and the female gamete is called an ………...
Gametes contain half the number of chromosomes of a normal body cell. In
humans this means an egg and sperm only contain …………. chromosomes. When
the sperm and egg fuse the fertilised egg contains a full complement of
……………. chromosomes (………. pairs).
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4. Copy the following diagram into your jotter and complete it by adding the
correct number of chromosomes into the nucleus of each cell (23 or 46):
Sperm Cell
+
Fertilised Egg Cell
Egg Cell
=
5. Now go back and add a definition for gamete and chromosome into your
glossary.
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Species
LI To understand the definition of the term species
Dogs are members of the same species but there is still a lot of variation
between different breeds of dog.
1. Draw this table and it’s heading into you jotter:
Table – Similarities and differences between different breeds of dog
Similarities
Differences
1.
1.
2.
2.
3.
3.
4.
4.
What to do
2. Study these 4 pictures of different dog breeds and note the similarities
and differences that all these dogs share.
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3. Draw the following table and it’s heading into your jotter:
Table – Similarities and differences between a horse and a donkey
Similarities
What to do
Differences
1.
1.
2.
2.
3.
3.
4.
4.
4. Study the two pictures below of a horse and donkey. Note in your table
the similarities and differences that they share.
Horse
Donkey
The picture below shows a mule. A mule is the result of breeding a horse and
donkey. Mules are sterile. This is how we can tell whether or not two organisms
are members of the same species.
Mule
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Interbreeding dogs produces fertile off-spring, even if great variation exists
between two breeds. This shows dogs are members of the same species. If two
organisms interbreed and produce sterile off-spring (e.g. when a horse and
donkey interbreed to produce a mule), this shows that those two organisms are
members of different species, despite their similarities.
5. What is the result of breeding a horse and donkey?
6. Does this tell us if a horse and donkey are members of the same species
or not?
7. Are you surprised by this result? Explain your answer by discussing the
similarities and differences you noted.
A species is a group of organisms that are able to interbreed and produce
fertile off-spring.
8. Go back to your glossary page and add the definition for species to your
table
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Chromosome Mapping
LI To understand that chromosomes are inherited from our parents and are
arranged in matching pairs
Chromosomes are arranged in matching pairs – there are 23 pairs of
chromosomes in a human body cell (23 x 2 = 46). We can see the arrangement of
chromosomes in their pairs using a chromosome map called a karyotype. In each
pair, one chromosome is from the mother and one chromosome is from the
father.
mother’s chromosome
father’s
chromosome
Child’s karyotype
Karyotype
What to do
1. Find your diagram of a “Human karyotype” in your diagram pack and stick
it in your jotter
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2. Create a key at the side of the diagram like the one below:
blue
pink
Father’s Chromosome
Mother’s Chromosome
3. Colour one chromosome in each pair blue and one chromosome in each pair
pink according to your key.
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Genes and Alleles
LI To understand that we inherit two forms of every gene and these are
called alleles
Chromosomes are split into sections called genes. Genes carry genetic
information that will determine our physical characteristics.
1. Copy the diagram below into your jotter:
Gene for hair colour
Gene for eye colour
Chromosome
Gene for blood group
Gene for hair type
Gene for freckles
2. Go back to your glossary and add the definition for gene.
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As you know, chromosomes are arranged in matching pairs. In each chromosome
pair, one is from the father and one is from the mother. This means that we
inherit two copies of each gene – one copy from each parent.
Genes can have different forms, for example in eye colour there can be a brown
form of the eye colour gene and a blue form of the eye colour gene. It is
possible to inherit two different forms of the same gene:
Father’s Chromosome
Mother’s Chromosome
Gene for brown
eyes
Gene for blue eyes
Chromosome Pair
There can be more than one form of the same gene. Different forms of the
same gene are called alleles.
Discuss with your neighbour: What colour of eyes would a child have if they
inherited two different forms of the eye colour gene?
(example: the blue colour gene from the mother and the brown eye colour gene
from the father)
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When two different forms of a gene (alleles) are inherited, the resulting
characteristic will depend on gene dominance.
Genes can have dominant or recessive forms. A dominant allele hides the
recessive allele (as though it was never there!!)
So, if brown eyes were dominant and blue eyes were recessive, the child would
have brown eyes because the blue eyed allele is hidden by the brown eyed allele.
We represent alleles using letters, and show dominant and recessive alleles
using capital letters for dominant alleles and small letters for recessive alleles.
In the example of eye colour:


Brown eyes – B (a capital letter because brown is dominant)
Blue eyes – b (a small letter because blue eyes are recessive)
3. Copy and complete (using words below) the passage below using the
information from the passage above to help you:
We inherit t……… copies of the same g…………… – o…….. from each parent.
There can be more than one form of the s……..…… gene. These are called
a……..……….. For example – there is an eye colour gene. But this might have a blue
a…………….. and a brown a………….…… (two different forms of the same gene).
Some alleles hide other alleles – these are d……………..……. alleles, and the ones
that are hidden are r…………………………. If the brown eyed a……..………. was dominant
and the blue eyed a……………… was recessive, then the child born would have
b……………. eyes because the b……………. eyed a……………… was hidden by the
b…………….. eyed allele.
Genes are represented using l…………..…. Dominant alleles are given c………………
letters, whilst recessive alleles are given s…………..……. letters.
Example:
 B……………. eyes – B (a capital letter because it is ……………………..)
 B…………… eyes – b (a small letter because it is ……..……………………)
WORDS-
recessive
one
gene
same
alleles
allele
brown
blue
dominant
4. Go back and add the definition of “allele” to your table.
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Genotype and Phenotype
LI To understand the definition of the term genotype and phenotype
We have already found out that genes are shown using letters. The genes that
you inherit are called your genotype. What you physically look like is called your
phenotype.
Hint: remember
- genes you inherit = genotype
- physical characteristic = phenotype
Example:
A person inherits one dominant allele of a gene for curly hair (T) from her
father and one recessive allele of a gene for straight hair (t) from her mother.
Therefore her genotype = Tt (the genes she inherited).
But, her physical characteristic (phenotype) is curly hair (what she actually
looks like).
Genotype – the alleles of a gene that are inherited by an organism for a
particular characteristic
Phenotype - the physical appearance of an organism (what you actually look like)
1. Go back and add the definition of “genotype” and “phenotype” to your
glossary.
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2. Complete the questions below in your jotter.
Q1 Below is a list of genotypes and phenotypes. Write the list in your jotter and
beside each note if it is a genotype or phenotype. The first has been done for
you.
a.
b.
c.
d.
e.
f.
Blue eyes – phenotype
Gg
Blonde Hair
Freckles
TT
Blood group O
Q2. Joe has brown hair. Joe has had his chromosomes mapped and knows he has
one allele for brown hair and one allele for black hair. Which allele was dominant
- Brown or black haired gene?
Q3. Liz has blue eyes. Blue eyes is a recessive trait, could Liz also have
inherited an allele for brown eyes (a dominant characteristic)?
Explain your answer
What to do
Q4. Read the passage below and answer the questions that follow:
Brian has freckles. He has blonde hair like his dad and green eyes like his mum.
Brian is 6 foot tall and is training to be a rugby player like his dad who is just as
tall. Brian sometimes gets teased by his friends for having attached ear lobes.
a. List all the phenotypes that appeared in the passage.
b. Brian knows he inherited one allele for blonde hair (from his dad) and one
for red hair (from his mum):
i. Which form of the hair colour gene was dominant?
ii. What name is given to more than one form of the same gene?
c. Choose one phrase from the passage that supports the statement that
characteristics are inherited.
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3. Find your “mini-me” diagram in your diagram pack. Complete the “mini-me” by:
What to do
a. adding your “phenotype” (physical characteristics)
b. Noting which of your characteristics you think you have inherited from
your mother and which you have inherited from your father
AND/OR
The characteristics you share with your siblings
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Genetic Cross
LI To carry out a simple genetic cross and predict the characteristics of
off-spring
Your teacher will show you a video: GCSE Genetics
You now know that your physical characteristics (phenotype) depend on the
alleles you inherit. If you inherit a dominant allele you will have a dominant
characteristic – even if you inherited a recessive allele!! You only inherit a
recessive characteristic if you inherit two recessive alleles.
We describe the genotype of a person, based on the genes they inherit:
If they inherit two alleles that are the same, their genotype is called
homozygous (example – BB for brown eyes, or bb for blue eyes).
If they inherit two alleles that are different, their genotype is called
heterozygous (example – Bb for brown eyes).
1. Draw this diagram into your jotter:
Homozygous
Homozygous
Heterozygous
3. Add a definition for homozygous and heterozygous into your glossary.
Discuss with your neighbour: What characteristics would be present in the offspring if the father was homozygous for brown eyes (BB) and the mother was
homozygous for blue eyes (bb)?
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We can work out the off-springs genotype and phenotype using a Punnett
square:
B
B
b
b
1. Listen as you teacher explains how to use a Punnett square
2. Draw the Punnett square above into your jotter and complete it
3. Your teacher will give you several examples to work through
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Extension work;
What to do
Read the following passage and complete the questions that follow:
In genetics we use the letter “P” to symbolise the parent generation. The first
generation of off-spring is called the first filial generation, represented by the
symbol “F1”. If two members of the F1 generation are bred (crossed) then the
resulting off-spring are known as the Second filial generation and they are
represented by the symbol “F2”.
True-breeding is the term used to describe a situation when two homozygous
parents are crossed. These parents are both true-breeding for one
characteristic. For example, one parent will be true-breeding for brown eyes
(BB) and one will be true-breeding for blue eyes (bb). All the members of the F1
generation are heterozygous and display the dominant characteristic (e.g. Bb brown eyes).
If two heterozygous members from the F1 generation are bred (crossed) then
the hidden recessive characteristic carried by both F1 individuals may appear in
the F2 generation.
1. Copy and complete the statement below:
In genetic crosses symbols are used to show each generation:
Parent generation = ……………
First Filial generation = ………………
Second Filial generation = ………………
2. Which generation are bred to produce the first filial generation?
3. When both parents are homozygous for a particular characteristic, what will
the genotype of all members of the first filial generation be?
4. What name is given to a cross between two parents who are both homozygous
for a particular characteristic?
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5. Which generation are bred to produce the second filial generation?
6. Which characteristic is hidden in the first filial generation but may appear in
the second filial generation?
7. Complete the “genetic cross” diagram in your diagram pack. Use your
knowledge of punnett squares and the information above to help you.
8. Circle in red all the individuals who could be described as true-breeding on
your genetic cross diagram. Make this key in your jotter.
9. Add a definition for true-breeding into your glossary.
10. Add the following Black Box statement into the box below your “genetic
cross” diagram:
This is a true breeding cross for 3 reasons:
1. Both parents are homozygous for one characteristic
2. All members of the F1 generation will display the dominant
characteristic (black fur) only
3. The F2 generation will show both dominant and recessive characteristics
in a 3:1 ratio
Predicted vs Actual ratios
Listen as your teacher explains why in a true-breeding cross, sometimes the
predicted ratio is different from the actual ratio.
It is predicted that in a true breeding cross, the F2 generation will display the
dominant and recessive traits of the original parents in a 3 dominant:1 recessive
ratio. However, often the actual ratio is different from the predicted ratio.
There are several reasons for this:
1. Fertilisation is a random process, involving an element of chance.
2. Number of off-spring produced is often too small.
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Reebops
LI To apply my knowledge of genetics and create a “Reebop Baby”
What to do
Collect the following equipment:


One pack of Blue chromosomes (dad)
One pack of Pink chromosomes (mum)
1. Lay the chromosomes face down on the desk in their pairs (separated
into the mum’s and the dad’s chromosomes)
2. Randomly choose one blue chromosome from the dad’s chromosomes and
one pink chromosome from the mum’s chromosomes from each pair.
3. Match the chosen pink and blue chromosomes with their corresponding
pair (hint: they should be the same length)
4. Draw the following table in your jotter:
Genotype (letters)
Phenotype (physical characteristic)
5. Complete the table using the Key below:
AA – 2 antenna
Aa – 2 antennae
aa – 1 antenna
QQ – red nose
Qq – red nose
qq – yellow nose
EE – 2 eyes
Ee – 2 eyes
ee – 3 eyes
DD – 3 body segments
Dd – 3 body segments
dd – 2 body segments
MM – 2 hump
Mm – 2 humps
mm – 1 humps
TT – curly tail
Tt – curly tail
tt – straight tail
LL – blue legs
Ll – blue legs
ll – red legs
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Draw a diagram in your jotter of what you think your Reebop Baby will look like
based on the characteristics it has inherited.
What to do
6. Now collect the correct equipment from the list below to create your
Reebop using the genetic instructions you have created in your table:







Body segments
Humps
Antenna
Tail
Eyes
Nose
Legs
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Sex Determination
LI To understand how sex is determined by carrying out a simple genetic
cross
Discuss with your neighbour – what chromosomes must an individual inherit to
be:
- male?
- female?
1. After class discussion – note this in your jotter
Revision Bite:
Answer the following questions in full sentences in your jotter:
2. What name is given to sex cells?
3. What is special about a sex cells chromosomes?
4. Copy the black box statement below and the diagram into your jotter:
Sex cells are produced by Gamete mother cells. Gamete mother cells are
present in the testes of the male and the ovaries of the female.
=
Female Gamete Mother Cell
X
Male Gamete Mother Cell
X
X
Y
Female Gametes
X
Male Gametes
X
Every female gamete gets an X
chromosome
X
Y
Half the male gametes receive an
X and half receive a Y
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We can use this information to determine the chance of parents having a girl or
a boy.
1. Complete the punnett square below:
X
Y
X
X
2. Colour in the squares in the punnett square that show a boy in blue
3. Colour in the squares in the punnett square that show a girl in pink
[Hint remember:
male = XY
female = XX]
4. Express as a percentage the number of off-spring who will be male, and the
number that will be female.
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Mutation
LI To identify some of the causes of mutation and give examples of genetic
mutation in plants and animals
A mutation occurs when an organism’s genes or chromosomes become altered in
some way.
1. Go back to your glossary and add the definition of
Down’s syndrome
Some mutations are detrimental to development of an organism.
For example, in humans Down’s syndrome occurs when a gamete carrying an
extra chromosome is fertilised, forming a zygote with 47 chromosomes rather
than 46. The presence of just one extra chromosome in Down’s syndrome leads
to mental deficiency and a characteristic appearance.
ultrasound
Amniotic Fluid
Foetus
Amniocentesis:
During pregnancy the amniotic fluid surrounding an embryo contains skin cells.
Amniocentesis is a technique used to sample the skin cells, and these can be
tested for abnormalities before birth. Down syndrome is one of the
abnormalities tested for. Amniocentesis only gives an indication that the child
might have an abnormality, but some parent’s will choose to terminate a
pregnancy if they suspect the child may have inherited an abnormality.
Amniocentesis can also lead to a miscarriage even if the child is healthy.
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2. Describe the genetic mutation that occurs in the chromosomes of a person
suffering from Down’s syndrome.
3. What are the symptoms of Downs Syndrome?
4. Describe what happens during the Amniocentesis procedure
5. Below are some of the cases for and against amniocentesis. Can you arrange
them in the table below under the correct heading?

Amniocentesis allows parents to prepare if their child does have a genetic
disability

Amniocentesis can lead to miscarriage of a foetus

Amniocentesis cannot say for certain that a foetus has an abnormality
and therefore parents might choose to terminate a child, even though it
may be healthy.

Amniocentesis allows parents to decide whether or not to maintain a
pregnancy if their child has a genetic abnormality
Amniocentesis Arguments
For
Against
Debate
6. Choose an argument above and prepare a short speech that you will give to
the class as to why Amniocentesis should or should not be allowed.
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Useful mutations (take this sub-heading in your jotter)
Although most mutations are detrimental to the organism, some mutations can
be useful. For example, some plant species possess an extra complete set of
chromosomes due to a chromosome mutation. These plants are known as
polyploids. Polyploid strawberries are much larger than normal strawberries,
polyploid tomatoes contain extra vitamin C, polyploid wheat produce more flour.
6. What is the chromosome mutation that occurs in polyploids?
7. Give 2 examples of polyploid fruits and their useful mutation.
Mutagenic Agents
Naturally occurring mutations are rare and therefore mutation is slow. There
are some mutagenic agents that speed up the rate of mutation: nuclear radiation
(atomic), ultra-violet light (sunlight – leads to mutation in skin cells and may lead
to skin cancer) and x-rays (pregnant woman are not recommended for x-rays
past a certain point in their pregnancy). In Down’s syndrome, the rate of
mutation increases as the mother’s age increases, so the older the mother, the
greater the chance of a child with Down’s syndrome.
8. Take the sub-heading “Mutagenic Agents”. Then copy and complete the
sentence below using information in the above passage:
The rate of mutation can be increased by ……………………….. ………………….., such as:
1. ………………………. radiation
2. ……………………. ………………………… (UV) light
3. X-rays
4. The ………………… of the mother
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There have been many fictional representations of mutations in Humans, such as
the X-Men comics. Some scientists believe that as the human species continues
to evolve there will be more mutations that occur in the human race that
benefit the species.
Watch the “X-men first class movie trailer”
What to do
9. Find the “Create your own Mutant” diagram in your diagram pack.
Complete the diagram by:

Describing which part of the mutants genetics have been altered (a
particular gene or chromosome?)

Describing the physical appearance of your mutant and any
additional powers they may possess

Drawing a labelled diagram of your mutant
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