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Key Area 2.4
Genetic information
Starter Activity:
Discuss the following questions with your
partner:
What are genes?
Where in your cells are your genes found?
What chemical makes up your genes?
What physical characteristics are controlled
by your genes?
Variation
Learning Intention:
To learn about how genes control the
physical appearance of an organism
Success Criteria:
Be able to define the terms chromosome,
DNA, gene and variation
Understand that physical characteristics
are inherited from biological parents
through sections of DNA
Family resemblance
Members of the same
family often look
similar.
Which parent do these
children look more
like?
Why do members of the
same family look similar?
Humans, like all organisms, inherit characteristics
from their parents. How are characteristics passed
on?
Characteristics pass on through reproduction.
Species
A species is a group of organisms who can
interbreed and produce offspring which
are fertile (able to reproduce).
All humans can interbreed so we are all
the same species.
Some unusual examples
• Some animals seem to be members of
the same species but are not.
• The animals may be able to interbreed
and produce young, but the young are
not able to reproduce.
• Two examples are mules and ligers.
X
=
A mule is infertile, so horses
and donkeys are not the same
species.
X
=
Variation
• Although the members of a species are
very similar to one another, they are not
identical.
• Variation occurs among members of a
species.
Variation
• Variation – differences that exist
among members of a species.
What is variation?
Differences due to inherited and environmental
factors that exist between members of a
species.
Human Variation
Examples of human variation include:
Height
Blood group
Weight
Tongue rolling
Handspan
Handedness
Shoe size
Hair Colour
Hair Type
Fingerprints
Freckles
Eye Colour
Heart Rate
Twig Video: Human Variation
Variation
Learning Intention:
To learn about how genes control the
physical appearance of an organism
Success Criteria:
Understand that physical characteristics
are inherited from biological parents
through sections of DNA
Starter
Variation
For some characteristics there are clear groups of
individuals.
•
Tongue rolling- can or cannot
•
Blood group – A,B,AB or O
•
Fingerprint patterns – whorls,
loops, arches
•
Shape of leaves on oak trees –
lobes, no lobes
•
Colour of petals on a flower
•
Seed colour in peas – green,
yellow, brown
Variation graphs
For any variation where the
data gives distinct groups,
a bar chart or pie chart can
be used.
NUMERACY
Human Variation
You will look at examples of variation within the class
and construct a table.
Activity 1
Complete the table in your booklet
identifying the characteristics of people
in the class.
Name
Ear lobes
attached
yes/no
Freckles
yes/no
Tongue roll
yes/no
Left/right
handed
Name
Ear lobes
attached
yes/no
Freckles
yes/no
Tongue roll
yes/no
Choose two of these variations, and draw a bar chart for each.
Left/right
handed
Measured variation
For some characteristics there are not clear
groups of individuals. Instead there is a broad
range of measured values.
•
Height of rowan trees
•
Weight of rabbits
•
Pulse rate in humans
•
Leaf size in geraniums
•
Weight of chestnuts from tree
•
Height in humans
Range of heights and sizes
Variation graphs
NUMERACY
In this type of measured variation, most individuals have heights in
the centre of the range, with few at the extremes. This type of
graph is called a histogram or frequency graph.
Activity 2
Complete the table in your booklet showing the
hand spans of people in the class. Then complete
the summary table and histogram.
Hand span (cm)
Less than 17.5
17.5
18
18.5
19
19.5
20
20.5
21
21.5
22 or over
Number of people
Total number of people
Hand span (cm)
Less than 17.5
17.5
18
18.5
19
19.5
20
20.5
21
21.5
22 or over
Number of
people (tally
mark)
Total number of people
Structure of DNA and
Genes
Genetic information
Learning Intention:
To learn about how genes control the
physical appearance of an organism
Success Criteria:
Be able to define the terms chromosome,
DNA, gene and variation
Understand that physical characteristics
are inherited from biological parents
through sections of DNA
What is DNA?
• DNA stands for
Deoxyribonucleic
Acid.
• DNA is found in the
nucleus of a cell.
• It is would up very
tightly into
structures called
chromosomes.
Chromosomes
• A chromosome is a threadlike structure
that carries genetic information.
Gene
Genes
• Chromosomes are split up into
smaller segments called genes.
• A gene is a section of a
chromosome that contains a piece
of genetic information e.g. the
gene for tongue rolling.
• We inherit half of our genes
from our mother and half from
our father.
• This means that two genes
control each characteristic.
How are genes inherited?
The parents
Homer has straight hair
Marge has curly hair
The families
Is hair curliness controlled by genes or by the environment?
Homer
• Homer has straight hair.
• Every cell in Homer has two
sets of genes.
• Homer’s has two straight hair
genes.
• We can show the straight hair
gene with a capital H.
• Homer’s genes: HH.
Marge
• Marge has curly hair.
• Every cell in Marge has two
sets of genes.
• Marge has two curly hair genes.
• We can show the straight hair
gene with a small h.
• Marge’s genes: hh
Making a new Simpson
• Homer makes sperm.
• Each sperm has one gene for
hair type .
• Homer only has straight hair
genes.
• So all of his sperm have
straight hair genes.
Homer’s Sperm
H
H
Making a new Simpson
• Marge makes eggs.
• Each egg has one gene for hair
type .
• Marge only has curly hair
genes.
• So all of her eggs have curly
hair genes.
Marge’s Eggs
h
h
Making a new Simpson
h
h
H
Hh
Hh
H
Hh
Hh
This type of diagram
is called a punnet
square.
Making a new Simpson
Hh
Hh
Hh
Hh
• 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
Hh
THEY ALL HAVE STRAIGHT HAIR!
• The straight hair gene is DOMINANT.
• Just one copy of this gene will give you that characteristic.
• The curly hair gene is RECESSIVE.
• You need two copies of the gene to have that characteristic.
Liking donuts
• Homer likes donuts
• Every cell in his body has two donut liking
genes.
• His genes are: D D
Homer’s sperm
D
D
Liking donuts
• Marge doesn’t like donuts.
• Every cell in her body has two donut
disliking genes
• Her genes are: d d
Marge’s Eggs
d
d
Making a new Simpson
d
d
D
Dd
Dd
D
Dd
Dd
Making a new Simpson
Dd
Dd
• Liking donuts is dominant
• Do the Simpson children like donuts?
Dd
Dd
Weight
•
Marge has normal weight.
•
Both of her weight genes are for normal
weight.
•
Her genes are: N N
•
If you have two identical genes, this is known
as true breeding. Marge is true breeding for
normal weight.
Marge’s Eggs
N
N
Weight
• Homer does not have normal weight. He is
overweight.
• Homer is true breeding for being
overweight. This means both of his weight
genes are for being overweight.
•
His genes are: n n
Homer’s sperm
n
n
Making a new Simpson
Nn
Nn
Nn
Nn
• Normal weight is dominant.
• What weight do all the Simpson children have – normal or
overweight?
Activity 3 – Homer and Marge
Cross Number
Homer’s
Homer’s genes
characteristic
Marge’s
characteristic
Marge’s genes
1
Likes beer
BB
Doesn’t like beer
bb
2
Plays sports
SS
Doesn’t play sports
ss
3
Burps
BB
Doesn’t burp
bb
4
Lazy
LL
Not lazy
ll
For each of the above characteristics, work out what their children are
likely to be like.
The next generation?
• Lisa has straight hair.
• Every cell in Lisa has two sets of genes.
• Lisa has one gene for straight hair (H),
which is dominant.
• She also has one gene for curly hair (h),
which is recessive.
• Lisa is not true breeding.
• Lisa’s genes: Hh
• Milhouse has straight hair.
• Every cell in Milhouse has two sets of
genes.
• Milhouse has one gene for straight hair,
which is dominant.
• He also has one gene for curly hair, which
is recessive, so he is not true breeding.
• Milhouse’s genes: Hh
• Milhouse’s genes: Hh
Milhouse’s sperm:
H
• Lisa’s genes: Hh
H
h
Lisa’s eggs:
h
The next generation?
What if Lisa and Milhouse have children?
H
h
H
HH
Hh
h
Hh
hh
The next generation
HH
Hh
Hh
• Straight hair is dominant.
• Imagine Lisa and Milhouse have 4 children.
• How many children will have straight hair?
• How many will have curly hair?
hh
Activity 4 -The next
generation
Cross Number
Lisa’s
characteristic
Lisa’s genes
Milhouse’s
characteristic
Milhouse’s
genes
1
Likes School
Ss
Like School
Ss
2
Good eyesight
EE
Bad eyesight
ee
3
Brave
Bb
Not brave
bb
For each of the above characteristics, work out what their children are
likely to be like using the punnet squares in your worksheet.
If you feel confident, you can try the extension exercise in the
booklet.
Variation
• We can see that not all of Lisa and
Milhouse’s children would be the same.
• This is because each child inherits a
slightly different set of genes from
their parents.
• This creates variation within families,
and variation within the population.
Starter
Say hello……to the Reebops
Activity 5 – Making Reebops
1. Open each envelope, take out the cards and sort
them out into Mum’s (pink) and Dad’s (blue).
2. Sort each set of chromosomes into pairs of the same
length. Now turn all the chromosomes over.
3. Randomly take one chromosome from each pair of
Mum’s chromosomes and place in a pile called ‘female
gamete’.
4. Randomly take one chromosome from each pair of
Dad’s chromosomes and place in a pile called ‘male
gamete’.
5. Put the unpicked chromosomes back in the envelope.
Fertilisation
1. Mix the two sets of chromosomes together. This is
what happens in fertilisation.
2. Sort out the chromosomes into size again.
3. Use the decoder key to decide what characteristics
your Reebop has. Write these in the table in your
booklet.
4. Now you can make your Reebop!
Decoder key
Characteristic
antennae
Decoder
AA = 2 antennae
Aa = 2 antennae
aa = no antennae
BB = 3 body
segments
Bb = 3 body
segments
bb = 2 body
segments
tail
TT = curly tail
Tt = curly tail
tt = straight tail
nose
NN = red nose
Nn = orange nose
nn = yellow nose
legs
LL = blue legs
Ll = blue legs
ll = red legs
sex
XX = female (pink XY = male (non
body)
pink body)
eyes
EE = 2 eyes
Ee = 2 eyes
ee = one eye
humps
HH = 1 hump
Hh = 1 hump
hh = 3 humps
body segments
Questions
1. Are there any baby Reebops that are identical?
2. How much genetic material does each parent
provide?
3. How is this genetic material passed on to the
children?
4. Why is there variation in families?