1. Overview of Cell Division Mechanisms
Chapter 9.1
Overview of Cell Division Mechanisms
AP Biology
Fall 2010

2. Objectives
Determine the function of mitosis, meiosis, and prokaryotic fission
Analyze the structural components of chromosomes

3. Mitosis, Meiosis, and Prokaryotes
Before cells reproduce, there must be a division of the nucleus and its DNA

4. Mitosis, Meiosis, and Prokaryotes
Mitosis and meiosis are eukaryotic nuclear division mechanism that lead to the distribution of DNA to new nuclei in forthcoming daughter cells

5. Mitosis
Mitosis is used by multicelled organisms for growth by repeated divisions of somatic cells
Responsible for:
Increases in body size during growth
Replacement of worn out or dead cells
Tissue repair

6. Mitosis Used by multicelled organisms
Plants, animals, fungi and single celled protists produce asexually by mitosis

7. Meiosis
Meiosis occurs only in reproductive cells that divide to form gametes or spores
Sexual reproduction
Gemetes kown as sperm and eggs develop from germ cells
Spores form in life cycle of protists, plants, and fungi

8. Meiosis

9. Prokaryotes
Prokaryotic cells reproduce asexually by an entirely different mechanism called prokaryotic fission

10. Prokaryotes

11. Chromosome Structure
Each chromosome is a molecule of DNA complexed with proteins
Eukaryotic species have a characteristic number of chromosomes
Before cell enters nuclear division, duplicates every chromosome
Forms two sister chomatids held together by centromere

12. Chromosome Structure

13. Chromosome Structure During early stages of mitosis and meiosis:
Duplicated chromosomes coil back on itself into highly condensed form

14. Chromosome Structure
Proteins called histones tightly bind to DNA and cause spooling into structural units called nucleosomes
Prevent tangling during nuclear division
DNA winds twice around histones

15. Chromosome Structure
Nucleosome: consists of part of DNA molecule looped twice around a core of histone proteins

16. Chromosome Structure Centromere: constricted region
Location is different for each type of chromosome, unique characteristic
Kinetochore: during nuclear division, located at centromere
Is docking station for microtubules that help move chromatids

17. Chromosome Structure

18. Review What is the point of structural organization of chromosomes?
What is the function of mitosis?

19. Answers
Tight packaging keeps chromosomes from getting tangled, also between cell divisions nucleosome packaging can be loosened in specific regions (enzymes gain access to heredity information that cell requires).
The function of mitosis is to increase in body size during growth, replacement of dead or worn-out cells, and repair of damaged tissues.