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 resemblanceMembers of the same family often look similar.

Which parent do these children look more like?

Humans, like all organisms, inherit characteristics from their parents. How are characteristics passed on?

Why do members of the same family look similar?

Characteristics pass on through reproduction.

SpeciesA 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

Eye Colour

Hair TypeHeight Tongue rolling Shoe size Hair Colour

Blood group Handspan Fingerprints Freckles

Weight Handedness Heart Rate

Twig Video: Human Variation

Examples of human variation include:

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

VariationFor 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 graphsFor 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 1Complete the table in your booklet identifying the characteristics of people in the class.

NameEar lobes attached yes/no

Freckles yes/no

Tongue roll yes/no

Left/right handed

                                                                                                                     

NameEar lobes attached yes/no

Freckles yes/no

Tongue roll yes/no

Left/right handed

                                    

Choose two of these variations, and draw a bar chart for each.

Measured variationFor 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

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.

NUMERACY

Activity 2Complete the table in your booklet showing the hand spans of people in the class. Then complete the summary table and histogram.

Hand span (cm) Number of people Total number of peopleLess than 17.5    

17.5    18    

18.5    19    

19.5    20    

20.5    21    

21.5    22 or over    

Hand span (cm)

Number of people (tally

mark)

Total number of people

Less than 17.5    17.5    18    

18.5    19    

19.5    20    

20.5    

21    21.5    

22 or over    

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 parentsHomer 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 SpermH 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

H Hh

Hh Hh

Hh This type of diagram is called a punnet square.

Making a new SimpsonHh HhHhHh

• 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 SimpsonHh

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

D Dd

DdDd

Dd

Making a new SimpsonDd DdDdDd

• Liking donuts is dominant

• Do the Simpson children like donuts?

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 spermn n

Making a new SimpsonNn NnNnNn

• Normal weight is dominant.

• What weight do all the Simpson children have – normal or

overweight?

Activity 3 – Homer and Marge

Cross Number

Homer’s characteristi

c

Homer’s genes

Marge’s characteristi

c

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 bb4 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 h

H h

• Lisa’s genes: Hh Lisa’s eggs:

The next generation?What if Lisa and Milhouse have

children?

H h

h

H HH

hhHh

Hh

The next generationHH hhHhHh

• Straight hair is dominant.

• Imagine Lisa and Milhouse have 4 children.

• How many children will have straight hair?

• How many will have curly hair?

Activity 4 -The next generation

Cross Number

Lisa’s characteristi

c

Lisa’s genes Milhouse’s characteristi

c

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 Reebops1. 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.

Fertilisation1. 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!

Characteristic Decoder

antennae AA = 2 antennae

Aa = 2 antennae

aa = no antennae

body segments 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 body)

XY = male (non pink body)  

eyes EE = 2 eyes Ee = 2 eyes ee = one eye

humps HH = 1 hump Hh = 1 hump hh = 3 humps

Decoder key

Questions1. 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?