1. Objective -1
Gene structure and organisation.

2. Why does one organism look different to another ?
1. Do the members of this family have any similar features ?
2. Are the members different in any ways ?
3. What reasons can you think of to explain these differences ?

3. How does variation come about?
Sexual reproduction
Genetic information is exchanged between the male and female gametes
These sex cells carry the information on genes

4. Inherited differences.
These are due to genes or the bits of message we get from a parents sperm and egg.
In plants the genes are in the pollen and ovule.
The genes are found in the nucleus of plant and animal cells.
Nucleus

5. The genes are in our cells.
In the nucleus
Where are they kept?

6. Chromosomes The genes are on long, string-like things called
What are they made of ?

7. DNA(DEOXYRIBONUCLEIC ACID) and Genes
DNA is a double helix molecule
A Gene is a length of DNA
Cells are made of proteins
Genes tell the cell how to put amino acids together to make the proteins
This determines what type of cell it is:-
e.g. haemoglobin is made for red blood cells or melanin is made for skin cells.

8. How many do you have in all of your cells except you sex cells ?

9. We have 46 of them in our cells.
What do you notice about them?

10. and half came from dad half came from mum
All our chromosomes are in pairs
and half came from dad
half came from mum
Where did we get each one from?

11. This means that genes are in pairs
Because… E E
Genes are on chromosomes.

12. Sex cells are special when it comes to chromosomes and genes.
They only have one of each, not the usual two.
Why is this?
Sex cells are designed to join together and so...
1 + 1 = 2

14. We can use these facts
to make predictions
about the features that
children will inherit from
their parents.

15. Inherited Differences in Humans.
Genes control the characteristics that develop.
1/2 the instructions come from the father and 1/2 come from the mother.
The new individual is genetically unique.

16. The same but different !
Variation