1. Chapter 10: Chromosomes, Mitosis and Meiosis Pgs 213-235
Biology 105
Chapter 10: Chromosomes, Mitosis and Meiosis
Pgs

2. Student Outcomes
Discuss the significance of information found on chromosomes.
Explain the cycle and significance of mitosis
Differentiate between asexual and sexual reproduction

3. Student Outcomes Explain the cycle and significance of meiosis
Distinguish between haploid and diploid cells

4. Genome A large amount of coded genetic information (DNA)
The genome is organized into units called genes.
Human genome project maps out 25 chromosomes: plus X and Y (23rd pair) plus mitochondria chromosome
Several organisms’ genomes have been mapped out including the humans.

5. Chromosomes Are made up of chromatin (DNA and proteins)
Number will vary from organisms to organism. Human =46, fruit fly =8 (most plant and animals will be between 8-50)
The number is not as important as the amount of information found on each.
Map of the human chromosomes-Karyotype
Chromosomes means colored body – however, they are virtually colorless. They can though be stained. Chromososme – one type of roundworm has 2, a fern has 1000

6. Prokaryotic vs Eukaryotic
No true nucleus in prokaryote so genetic material is one circular DNA molecule
Eukaryotes have much more DNA than Prokaryotes
Histones (proteins) with DNA form nucleosomes
The Prokaryotic DNA is about 1000 times larger than the cell itself. It is twisted and folded to fit inside the cell (proteins help accomplish this)

7. Nucleosomes Prevent DNA strands from becoming tangled
Each nucleosome consists of 8 histone molecules wrapped by a DNA strand of 146 nucleotide pairs. See page 216

8. Cell reproduction Known as Cell Cycle Usually lasts between 8-20 hours
Cell cycle consists of Interphase and ‘M’ phase
M phase consists of Mitosis and cytokinesis
Usually lasts between 8-20 hours
Not all cells divide – nerve, skeletal muscle and RBC do not divide
Prokaryotic cells can divide as quickly as 20 minutes.

9. Interphase Divided into G1, S and G2 phase.
Interphase takes up about 90% of the cell cycle time.
‘Normal’ cell phase, nucleus is present

10. G1 Phase No DNA synthesis occurring Growth occurs
Enzymes and proteins required for DNA become active

11. S Phase
‘Synthesis’ phase
DNA replicates – doubles itself

12. G2 Phase Increased protein synthesis in preparation for division
Shortest of the interphase 3 phases
Leads the cell into mitosis

13. Mitosis Continuous phase, although divided into 4 stages.
Prophase-chromosomes compact and become visible, scattered around the cell, nucleus disappears. Sister chromatids are joined together at the two centromeres. Centrioles move to opposite ends (poles) Microtubules connect chromosomes to the pole region.
Kinetochores form – attach to the centromere and to the microtubules. Asters form the pole region.

14. Mitosis cont. Metaphase Chromosomes align at the middle
Chromosomes completely compact and most visible in this stage.
Each chromatic attaches to microtubules and begins to move to poles.

15. Mitosis cont.
Anaphase
Sister chromatids separate and move to poles lead by the centromere.
Telophase
Final stage- nuclear membrane forms around each set of chromosomes, microtubules disappear.

16. Cytokinesis
Microfilaments associated with the plasma membrane forming a new membrane down the middle of the cell. Two daughter cells are formed. (Identical)

17. Checkpoints
Cell will regulate itself and not divide if it detects abnormalties.
Protein kinases are enzymes that control this.
Drugs can also mimic this ability as well as hormones like steroids.

18. Reproduction Asexual Sexual
Result of mitotic divisions, clones of the parent. Advantage of not finding a mate. Organisms will bud, split or fragment to reproduce.
Sexual
Union of two sex cells called gametes. A single fertilized cell is formed called a zygote.
Advantage of sexual rep. is genetic diversity.

19. Meiosis
Process of 2 divisions - producing sex cells with ½ the number of chromosomes per cell -haploid
Once fertilization takes place – the normal diploid number of chromosomes is obtained.
Human diploid = 46, haploid =23

20. Meiosis cont. Divided into Meiosis I and Meiosis II
No doubling of chromosomes between the two.
In Meiosis I ‘crossing over’ occurs during prophase.
Meiosis II is identical to the process of mitosis.

21. Formation of sex cells-Meiosis
Forms sex cells known as gametes -gametogenesis
Male gametes – spermatogenesis (4 sperm cells for each cell that enters meiosis
Female gametes – oogenesis (one egg –ovum is formed and 3 polar bodies)
Polar bodies received little cytoplasm or nutrients resulting in small cells and a large ovum.