1. Genes and Chromosomes
1.1 page 4
1.2 page 12-13

2. What is a gene?
A unit of inheritance, a section of DNA, a sequence of bases on a DNA molecule that codes for a particular characteristic
The difference between one gene and the next is the:
Order of bases along the DNA strand
Length of the DNA strand
What is a genome?
The total amount of DNA in an organism (Including its genes)
Genes tell cells what to do by prescribing what proteins the cell makes.
Genes

3. What is a gene?

4. Switching Genes on and off
Every body cell in an organism has the same set of genes called a genome, but not all genes are active.
Some have to be switched on to act and some have to be switched off at different stages in the life of a cell.
This is why hairs do not grow on the stomach lining and cheek cells do not grow on toenails.
Image what we would look like if the hair gene was not switched off!!
Switching Genes on and off

5. Chromosomes

6. Chromosomes Chromosomes are composed of DNA and protein.
Inside somatic cells (Eg: skin cells):
46 chromosomes (half come from your mother and half come from your father)
They are grouped into 23 pairs
Inside gamete cells (sperm and eggs):
23 chromosomes
Females XX (sex chromosomes)
Males XY (sex chromosomes)
Chromosomes
1 pair of chromosomes

7. Sex determination

8. Diploid number (2n) : The number of chromosomes in somatic cells
Haploid number (n): The number of chromosomes in gametes (sperm and egg cells).
Half the diploid number
Diploid number (2n) : The number of chromosomes in somatic cells

9. Karyotype Karyotype: All chromosomes paired and arranged in order
Homologous: pair of chromosomes (they are the same length and have genes at the same location).
One is inherited from the mother and one from the father of an individual

10. Chromosomes

11. Relationship between DNA, genes and chromosomes

13. Organism
Number of Chromosomes in a gamete (haploid)
Number of chromosomes in an organism (diploid)
Human 46
Dog 39
Cow 30
Potato 48
Fruit Fly 8

14. Organism
Number of Chromosomes in a gamete (haploid)
Number of chromosomes in an organism (diploid)
Human 23 46
Dog 39 78
Cow 30 60
Potato 24 48
Fruit Fly 4 8

15. Summary Somatic Cells: Gamete Cells: Non sex cells (autosomes)
46 chromosomes
Diploid
Grouped into 23 pairs
Summary
Gamete Cells:
Sex cells (eggs and sperm)
23 chromosomes
haploid

16. Making New Cells
Chapter 1.2 page 10

17. DNA Replication

18. DNA replication is the process of copying a double-stranded DNA molecule
Before DNA replication occurs, the two strands must be separated by an enzyme called DNA helicase, breaking the hydrogen bonds between the DNA strands.
DNA Replication

19. DNA Replication

20. Cell division Mitosis Meiosis production of 4 gametes
There are 2 types of cell division:
Mitosis
division of somatic cells into 2.
Meiosis production of 4 gametes

21. Mitosis
Produces two daughter cells that are identical to the parent cell.
This type of cell division is involved in growth and repair of the body.
Cell divides once into two cells

23. start
Stages of Mitosis

25. Meiosis Division of gametes
The parent cell divides twice and results in 4 daughter cells not identical to the parent cell. This gives us variation.
Each cell contains 23 single chromosomes
Meiosis occurs in the ovaries and testes
Cell divides twice into 4 cells
Meiosis

26. Activity Worksheet

27. Mitosis

28. Meiosis