1. Cell Division

2. Cell Continuity Aristotle: Spontaneous Generation
Continuity of Life – living things arise from other living things of the same type. (1800s)

3. Cell Structure Nucleus consists of strands called DNA
DNA = Deoxyribonucleic acid
DNA arranged in structures called chromosomes

4. Chromosomes Every organism has a definite number of chromosomes
E.g. Humans (46), Worms (2)

5. Chromosomes
Cells NOT dividing – Chromosomes are elongated and interwoven (Chromatin)
2. Cells ARE dividing – chromosomes shortened and distinguishable.

6. Genes Located randomly along chromosomes. May be thousands on a gene
Have the information to make particular proteins.
E.g. Protein = Enzyme
Units of Inheritance
E.g. Eye Colour, skin colour, shape of face etc…
All Genes in an organism = genome

7. Human Genome Project
June 2000 – all positions of the genes in human cell found.
About 25,000 genes
Store Information in a database
13 year project
Ongoing work – structures & functions

8. Reproduction Asexual – bacteria Sexual – plants, humans
Organisms that reproduce sexually produce sex cells called gametes.

9. Gametes Each gamete has a single set of chromosomes…..why?
Each normal (somatic) cell has a double set of chromosomes.

10. Haploid & Diploid Cells
Haploid – single set of chromosomes, i.e. one of each type of chromosome
Represented by ‘n’
E.g. Eggs & Sperm = 23 chromosomes (n=23)

11. Haploid & Diploid Cells
Diploid – two sets of chromosomes, i.e. two of each type of chromosome
Represented by ‘2n’
E.g. somatic cells = 46 chromosomes (n=46)

12. Cell Cycle

13. Interphase Cell is not dividing 90% of cycle Chromosomes = chromatin
New organelles being developed (mitochondria / chloroplasts)
Chromosomes making identical copies of themselves….

14. Chromosome

15. Mitosis

16. Mitosis Produces 2 identical daughter cells
Number & Structure of chromosomes identical to parent cell.
Uses: Growth and Repair, asexual reproduction

17. Stages of Mitosis
Interphase
Prophase
Metaphase
Anaphase
Telophase

18. Interphase Chromosomes = chromatin
New organelles being developed (mitochondria / chloroplasts)
Chromosomes making identical copies of themselves….

19. Prophase (Early)
Chromatin shorten and appear as two chromatids, joined by a centromere.
Nuclear membrane starts to disappear
Centrioles go to opposite sides of cell

20. Prophase (Late) Nuclear membrane completely gone.
Spindle fibres (protein) form out of the centrioles at opposite poles

21. Metaphase Chromosomes line up along equator of the cell.
Attach to spindle fibres

22. Anaphase Spindle fibres contract.
Pull apart chromosomes by centromeres
Occurs rapidly
Recognised by U and V shapes of chromosomes

23. Telophase Membranes start to reform
Spindle fibre breaks down into cytoplasm
Cell begins to split in two….

24. Telophase – Animal Cells
Plasma membrane divides cytoplasm in two - cytokenisis

25. Telophase – Plants Cell plate divides the cytoplasam in half.
Cell wall starts to form on both sides of it.

26. Interphase Chromosomes return to chromatin
Each cell starts to produce new organelles
A store of energy is gathered.

27. Definition and two causes
Cancer
Definition and two causes

28. What is Cancer? A large group of almost 100 diseases
Two main characteristics:
Uncontrolled growth of cells in the body
Ability of these cells to migrate to distant sites

29. What Causes Cancer? A mistake in the genetic code of the cell
Causes the cell to grow without control
In 90% of cases, the mistake is not inherited.
Often caused by exposure to carcinogens.

30. Carcinogens Factors that cause the DNA inside a cell to alter
Mutation of DNA
Mutations causes cells to become immortal

31. Carcinogens Physical – radiation, e.g. X-Rays, Sunlight and asbestos
Chemical – Cigarette smoke, Vinyl Chloride
Biological – Viral or bacterial, e.g. Hepatitis B.

32. Meiosis
Reduction – Division

33. Meiosis Produces 4 un-identical daughter cells
Number of chromosomes halved
Diploid→ Haploid
Produces gametes
Genetically varied daughter cells
Uses: Sexual reproduction, Genetic Variation