Biology B

1. Cell Reproduction

2. Why Do Cells Divide???
• DNA Overload - information overload too
much cell to make proteins for.
• Materials Exchange Problem – Surface Area
to Volume Ratio
• Injury
• Depletion of Cells from natural death.

5. Human Chromosomes
23 Homologous Pairs
homologous pairs= a matching pair of
chromosomes, one from each parent

6. • Number of
Chromosomes chromosomes depends
on characteristics of
species
• Examples:
• Humans 46 (23 pr)
Earth worm 36 (18pr)
• Fly 8 ( 4 pr)

7. Time for cell division
depends on type of cell
bacteria completes cycle in 22 minutes
nerve cell some only once in entire life
liver cell may take 1 year

8. G1 ~ intense activity & cell growth
S phase ~ DNA replication ( will copy every
chromosome)
G2 ~ prepares for mitosis
usually shortest part of interphase
organelles needed for mitosis are made now

10. Go to Video Clips

11. Stages of Mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase

12. Prophase
• Mitosis begins (cell begins to divide)
• Centrioles (or poles) appear and begin to
move to opposite ends of the cell.
• Spindle fibers form between the poles.

14. All these cells are in prophase

16. Metaphase
• Chromosomes line up at the equator of
the cell.
• Animal cell Plant Cell

17. Spindle fibers attach to the
chromatids

21. Anaphase ~ Chromatids (or pairs of
chromosomes) separate and begin to
move to opposite ends of the cell.
Animal Cell Plant Cell

24. Telophase
Two new nuclei form.
Chromosomes appear as chromatin
(threads rather than rods).
Mitosis ends.
Animal Cell Plant Cell

29. Cytokinesis
Cell membrane moves inward to create
two daughter cells – each with its own
nucleus with identical chromosomes.

31. Division
of
Prokaryotic
Cells
(binary
fission)

32. http://www.biologycorner.com/re
sources/mitosis-animated.gif

34. More
Practice

39. Cell Cycle

40. In lab, we will be looking at the
tip of a plant leaf, looking for the
different stages of mitosis

41. end