1. Cell Division
Ch 10 & 11
Sections 10-2, 10-3 & 11-4

2. Reproduction of Prokaryotes
Prokaryotes reproduce through a process called binary fission
The single, circular chromosome (which is attached to the plasma membrane) replicates
The cell grows & elongates, separating the two chromosomes
The plasma membrane and cell wall pinch inward, eventually forming two daughter cells

4. Eukaryotic Chromosomes and Cell Division
Almost all of a eukaryotic cell’s genes are found in the cell’s nucleus, and are grouped into multiple chromosomes
Chromosomes are only visible when a cell is in the process of dividing
The rest of the time, the DNA + protein threads exist as a diffuse mass called chromatin

5. Chromosomes Chromosomes: Found in eukaryotic cells
Pass genetic information from one generation to the next
Made up of DNA
The cells of every organism have a specific # of chromosomes EX: Fruit flies= 8 chromosomes, Humans= 46 chromosomes, carrot cells= 18 chromosomes
Each chromosome is composed of two chromatids

6. Eukaryotic Cell Division
Before dividing, the eukaryotic cell replicates its chromosomes
The two copies of the chromosome are called chromatids, and they are connected to each other at a region called the centromere
The pair of chromatids is still only one chromosome, and the chromatids are not considered chromosomes until they separate from one another

7. Chromatids Chromatids: 2 identical strands that make up 1 chromosome
During cell division, sister chromatids separate from each other
One chromatid then goes to each of the 2 new cells

8. The Cell Cycle
The Cell cycle= A series of events that cells go through as the grow and divide
Cells grow
Prepare for division
Divide to form 2 daughter cells
Each daughter cell then begins the cycle again

9. Events of the Cell Cycle
Events of the cell cycle can be divided into two major stages:
1. Interphase= Can be quite long. Divided into 3 parts
G1= Cells grow and increase their size; producing proteins and organelles
S= Chromosomes replicate, DNA is synthesized
G2= A time of metabolic activity; proteins needed for cell division are produced

10. Events of the Cell Cycle
Mitosis Phase (M Phase)
Consists of two processes: mitosis and cytokinesis
During mitosis, the chromosomes divide and are distributed into two daughter nuclei
During cytokinesis, the cytoplasm is divided into two
These two processes result in the production of two genetically identical daughter cells

12. Mitosis Mitosis= Process of cellular division. Divided into 4 phases:
Prophase
Metaphase
Anaphase
Telophase

13. Prophase
Prophase= longest phase of mitosis (50-60%) of total time required to complete mitosis
Chromosomes become visible
Centrioles (2 tiny structures located in the cytoplasm) separate and take opposite sides of nucleus
Condensed chromosomes attach to the spindle
Each chromosome has two chromatids joined at the centromere
Chromosomes coil more tightly
Nuclear envelope breaks down & nucleolus disappears
The chromosomes begin moving toward the center of the cell

14. Metaphase Metaphase= Lasts only a few minutes
The spindle is fully formed
All the centromeres of chromosomes line up in center of the cell
Microtubules connect centromere of each chromosome to the 2 poles of the spindle

15. Anaphase
Anaphase-
The centromeres of the chromosome come apart and the sister chromatids split & separate becoming individual chromosomes (called daughter chromosomes)
Chromosomes move into two groups near poles of the spindle
The cell elongates
Anaphase ends when chromosomes stop moving

16. Telophase Telophase- (basically the reverse of Prophase)
Cell elongation that began in anaphase continues
Chromosomes begin to disappear into tangle of dense material (Chromatin fibers uncoil)
Nuclear envelope reforms around each cluster of chromosomes
Spindles break apart and disappear
Nucleolus becomes visible in each daughter nucleus
Mitosis is complete
**CELL DIVISION HOWEVER IS NOT COMPLETE**

17. Cytokinesis
Cytokinesis- Division of the cytoplasm itself and is the final phase of cellular division
Usually occurs during the same time as telophase
In animal cells= cytoplasm is drawn inward and pinched into two equal parts
In plant cells= Cell plate forms causing a cell wall to form between the 2 divided nuclei

25. Regulating the Cell Cycle
Controls on Cell Division: Cell growth can be turned on and off depending on the situation
EX: if cells growing on a Petri dish are removed, the cells surrounding that now empty space will start dividing, filling in the area where the cells were removed

26. Uncontrolled Cell Growth
The consequences of uncontrolled cell growth in multicellular organisms can be very severe.
Cancer cells DO NOT respond to the signals that regulate the growth of most cells
They divide uncontrollably forming tumors
Some fail to respond to internal regulator proteins
Some fail to respond to external regulator proteins
Causes of cancer can be: smoking, radiation exposure, and even some viral infections

27. The Cell Cycle & Cancer Cancer is a disease of the cell cycle
Systems that control the cell cycle do not work in cancer cells
As a result, cancer cells divide excessively and can invade other body tissues
The excessive growth can result in an abnormal mass called a tumor

28. Tumors
Benign tumor-abnormal mass of normal cells; can cause problems if they grow in an organ; remain in their original site; can usually be completely removed by surgery
Malignant tumor-cancerous; capable of spreading to other body areas; displaces normal tissue; can form new tumors by breaking apart and spreading through the circulatory system (called metastasis)

29. Types of Cancers
Carcinomas-originate in the external or internal coverings of the body (skin)
Sarcomas-originate in tissues that support the body (bone and muscle)
Leukemias and Lymphomas-cancers of blood forming tissues (bone marrow, spleen, and lymph nodes)

30. Treatments for Cancer
Radiation- parts of the body with cancerous tumors are exposed to high energy radiation, which disrupts cell division (damage to ovaries or testes may cause sterility)
Chemotherapy-administration of drugs that disrupt cell division; some interfere with the formation or functioning of the spindle

31. Meiosis
Essential for the formation of gametes (ova and sperm) that will be used for sexual reproduction
Occurs in two consecutive cell divisions
Reduces the chromosome number by ½ (for humans, this means creating gametes that have 23 chromosomes)

32. Meiosis Vocabulary
Chromosomes – the number in each cell is cut in half and are different from each other and the parent cell. Gametes – are made during meiosis and are specialized cells involved in sexual reproduction. Tetrad – a structure containing 4 chromatids. (key to Meiosis) Pg. 276 Crossing-over – the exchange of portions chromatids during the pairing up of chromosomes. Pg. 276

33. Meiosis Vocabulary Chromosome Number P. 275
Homologous – chromosomes have a corresponding chromosome from the opposite-sex parent. Ex. Adult fruit fly has 8 chromosomes- 4 from male parent & 4 from female parent
Diploid - “two sets”; a cell that contains both sets of homologous chromosomes & genes. 2(N) Ex. Fruit fly has a diploid number of 8 so 2N=8.
Haploid – “one set”; a cell that contains one set of chromosomes & genes. (N) Ex. N =4

34. Human Chromosomes
Occur in pairs (there are 23 pairs) in somatic cells (typical body cells); these are called diploid cells (di=2)
Occur unpaired (a single set of 23) in the gametes; these are called haploid cells
The paired chromosomes in somatic cells are called homologous chromosomes, because they have genes for the same traits

36. Human Chromosomes 22 of the chromosome pairs are called autosomes
The 23rd pair consists of the sex chromosomes
Human females have a pair of sex chromosomes called X chromosomes (XX)
Human males have one X chromosome and one Y chromosome (XY)

37. Inheritance of Human Chromosomes
One chromosome from each pair is inherited from our mothers, and the other chromosome in the pair is inherited from our fathers
At the time of fertilization, the two haploid gametes (sperm and ovum) unite to form a diploid cell called the zygote
Fertilization results in the formation of a diploid cell, thus restoring the normal diploid number of human chromosomes
Meiosis occurs in reproductive organs

38. Meiosis I
DNA that is in special cells in the reproductive organs is copied.
The cells divide and 2 cells are formed which are different from each other and the parent cell.

39. Meiosis I Phases Pg. 276
Interphase I – DNA replication, forming duplicated chromosomes. Prophase I – Each chromosome pairs with its corresponding homologous chromosome to form a tetrad. Metaphase I – Spindle fibers attach to the chromosomes. Anaphase I – Fibers pull the homologous chromosomes toward opposite ends of the cell. Telophase I & Cytokinesis – Nuclear membranes form and the cell separates into 2 cells.

40. Meiosis II Cells divide again, but DNA is not copied first.
4 daughter cells are produced.
Each cell contains half of the number of chromosomes as the original parent cell.

41. Meiosis II
Prophase II – Meiosis I results in 2 (N) haploid daughter cells, each with half the number of chromosomes as the original cell.
Metaphase II – Chromosomes line up in a similar way to metaphase stage in mitosis.
Anaphase II – sister chromatids separate & move toward opposite ends of the cell.
Telophase II & Cytokinesis – Meiosis II results in 4 (N) haploid daughter cells.

42. Comparing Mitosis & Meiosis
Mitosis - 2 cells that are exactly alike & like parent.
Meiosis – 4 cell with each having only half the # of chromosomes as the parent cell and they are genetically different form one another.