1. AS Academic Tutorial 5. Stem Cell Division

2. So what are chromosomes?

3. Let’s revise the cell cycle
Cytokinesis:
cytoplasm divides
Nucleus divides
growth
new protein and organelles made
mitosis G1
Proteins needed for cell division made G2 S
DNA replicates

4. Stem Cell Cycle http://www.cellsalive.com/cell_cycle.htm

5. True or False?
The longest stage in the lifecycle of a stem cell is mitosis.
Mitosis is the division of a nucleus.
Replication of the DNA to produce identical sister chromatids occurs in the G2 phase.
The products of the cell cycle are genetically identical cells.
If there are 10 units of DNA in the original cell in G1, there are 20 in each of the new cells after cytokinesis.

6. So, before mitosis occurs…….
Cell at interphase
Protein synthesis
Organelle synthesis
DNA replication

7. A single chromosome at the beginning of mitosis
Has two chromatids,
as the DNA replicates during interphase before mitosis
centromere

8. Interphase – normal looking cells

10. 3 happenings occur
in prophase.
Early prophase
centrioles
nucleolus
DNA coils and condenses
Chromosomes take up stain

11. prophase
Centrioles move apart
Nuclear membrane breaks down
Nucleolus fades
Chromosomes continue to condense

12. Nucleolus disappears
Chromosomes continue to condense
What were the 3
happenings?

13. Prophase – wriggly worms!

14. Nuclear membrane broken down
metaphase
Chromosomes aligned on the equator
Nuclear membrane broken down
Each chromosome attached to spindle fibre by the centromere

15. Metaphase – spider’s legs exploding out of middle!

16. Anaphase
Centromeres divide and chromatids pulled apart

17. Anaphase

18. anaphase

19. Anaphase
Sister chromatids are pulled to opposite poles of the cell

20. Anaphase – fingers pulling apart

21. Telophase – two blobs in one cell

22. Cytokinesis

24. Mitosis Animations! http://www.cellsalive.com/mitosis.htm
Musical introduction!
3D good
Very clear - good

25. In a moment you will be preparing a root tip squash to look
for stained
cells like
these.
Let’s
recognise
the
phases!
Interphase

26. early prophase

27. prophase

28. metaphase

29. Anaphase

30. Early telophase

31. Telophase

32. Cytokinesis in a plant cell

33. Labels with arrow heads.
So now to the practical – see instructions in booklet page 4……Draw any 2 cells you find showing different mitotic phases, or 2 cells from the prepared slides.
Biological Drawings
Use the whole page.
Sharp pencil
No shading
No sketching
Labels with arrow heads.

35. When you have finished……..
Tidy all your equipment carefully away.
Start answering the quizzes in the booklet pages 1 – 3 and 5, and then go on to the exam questions pages They start easy and become challenging!
Page 8 should read “ Fig 5.1 shows drawings of nuclei, A to D, from 2 different plant species. Two of them show prophase of mitosis.”