1. Chapter 9 – The Cellular Basis of Inheritance
College Prep Biology
Mr. Martino

2. 9.1 All cells come from cells.
Repair and Growth
The outer layer of skin is dead, new living cells underneath replace the dead layer that rubs off.
Growth from infant to adult results in trillions of cell divisions.
Reproduction
Asexual reproduction = one cell splits into two new cells (bacteria); genetic clone
Sexual reproduction = two parents contribute to the offspring (sperm and egg); increases genetic variation

3. 9.2 Dividing Cells - Overview
Before cells can reproduce – they must undergo nuclear division
Mitosis: the division of regular body (somatic) cells
Meiosis: the division of cells that form sex (gamete) cells or germ cells
Chromosome: a DNA molecule and its proteins
Chromatin: long, thin threads of DNA and protein that eventually coils to become chromosomes as the cell gets ready to divide
Centromere: region that joins the sister chromatids

4. Ex. Humans have 46 chromo. in each somatic (body) cell
Chromosome # varies depending upon organism
Ex. Humans have 46 chromo. in each somatic (body) cell
Diploid: (2n) cells have a pair of each chromosome – somatic cells
Haploid: (n) cell with only 1 of each chromosome – gamete (sex) cells

5. 9.2 Cell Cycle G1 – growth S – DNA replication
Cell division replaces
old, worn out cells, or
damaged cells
Millions of cells divide every second in humans (nerve and muscles do not)
Cell cycle: sequence of events from when daughters cells are formed until they form new ones
Interphase: 90% of cell cycle – chromo. duplicate & cell grows
G1 – growth
S – DNA replication
G2 – growth & checking of chromo.

6. Chromo. are clearly visible
Division of most cells involves 2 processes that make op the M phase:
1. Mitosis: nucleus and chromo. divide
Chromo. are clearly visible
2. Cytokinesis: cytoplasm divides
Mitosis is unique to eukaryotes and very accurate

7. 9.3 Mitosis - Overview
Mitosis is a continuous process, but consists of 4 main stages:
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
Spindle apparatus: special microtublues that move chromosomes

8. Interphase By G2, most of contents has been doubled
Interphase: period of growth when the cell synthesizes new molecules and organelles
By G2, most of contents has been doubled
Chromatin has been doubled
At least 1 nucleolus is visible

9. Prophase
Chromatin fibers become more tightly coiled and folded – becoming chromosomes
Sister chromatids are joined at centromeres
Nucleoli disappear
Nuclear envelope disappears
Microtubules attach to chromosomes
Sisters are starting to move

10. Metaphase Mitotic spindle is fully formed
Chromosomes aligned at metaphase plate with centromeres on plate

11. Anaphase Begins when two sisters come apart – becoming chromosomes
ATP powers the pull of the chromosomes (centromeres first) toward opposite poles
Spindles not attached to chromosomes lengthen – elongating the cell
Ends when chromosomes reach poles

12. Telophase and Cytokenesis
Reverse of prophase
Cell elongation continues
Nuclei appear at poles
Chromosomes uncoil becoming chromatin
Nucleoli reappear
Mitotic spindle disappears
2 identical daughter nuclei have formed
Cytokinesis follows forming 2 identical cells

13. Animal Cell Mitosis

14. Plant Cell Mitosis

15. Division of Animal Cell Cytoplasm
Cytokinesis typically occurs in telophase, although it can begin in late anaphase
In animals, it is referred to as cleavage
Cleavage furrow: shallow groove on cell surface which is the first sign of cleavage
A ring of microfilaments acts like drawstrings and gradually pinches the cell in two

16. Division of Plant Cell Cytoplasm
Vesicles collect at center of cell and eventually fuse to form the cell plate
Cell plate grows outwards until it fuses with the cell membrane

17. Cell Division Video’s Bacteria Animation Embryogenesis Neuron Division
Plant and Animal Cell Division Movies

18. 9.4 Cancer cell grow and divide out of control
Tumors and Cancer
Benign tumor – abnormal mass of normal cells
Sometimes cause health problems but can usually be removed by surgery
Malignant tumor – masses of cells that result from reproduction of cancer cells
Cancer – disease caused by severe disruption of the cell cycle which may result in death
Metastasis – the spread of cancer cells from their original point

19. Cancer Treatment
Malignant tumors can be removed by surgery, difficult to remove all of the tumor.
Radiation treatment exposes the tumor to high levels of radiation (light or ionizing waves) that destroy the abnormal cells.
Side effects: damage to ovaries and testes
Chemotherapy treats the tumor with drugs that interfere with the spindle apparatus of the cancerous cells disrupting division
Side effects: damage to hair follicles and nausea.