1. Mitosis leads to duplicate cells. Parent cells  daughter cells1

2. Most prokaryotes—the bacteria and archaea—have less DNA than eukaryotes. They carry their genetic information in a single, circular chromosome, a strand of DNA that is attached at one site to the cell membrane ( FIGURE 6-3 ).
The most important part of a eukaryotic chromosome may be the DNA molecule, which carries information about how to accomplish the processes needed to support the life of the organism. But eukaryotic chromosomes (and some prokaryotic chromosomes) are made of more than just DNA. The eukaryotic chromosome is composed of chromatin, a linear DNA strand bound to and wrapped tightly around proteins called histones, which keep the DNA from getting tangled and enable it to be tightly and efficiently packed in an orderly manner inside the nucleus.

3. Prokaryotic Cell division: Binary Fission
When it is time for prokaryotes to reproduce, they use a method called binary fission, which means “division in two” ( FIGURE 6-4 ). This process begins with replication, the method by which a cell creates an exact duplicate of each chromosome.
The two newly created circular chromosomes attach to the inside of the plasma membrane at different spots from each other. The original cell, called the parent cell, then pinches in until it divides into two new cells, called daughter cells.
Binary fission is considered asexual reproduction, because the daughter cells inherit their DNA from a single parent cell and thus are genetically identical to the parent.

4. One specific antibiotic kills the whole colony of a type of bacteria because __
A. Bacteria are easy to kill
B. Bacteria are genetically similar
C. Bacteria undergoes sexual reproduction
D. Bacteria divides at a slow rate
Ans:B

5. Most cells are not immortal: mitosis generates replacements
Mitosis has just one purpose: to enable existing cells to generate new, genetically identical cells. There are two different reasons for this need ( FIGURE 6-10 ).
Growth
Replacement
Some other cells that must be replaced actually die on purpose, in a planned process of cell suicide called apoptosis. This seemingly counterproductive strategy is employed in parts of the body where the cells are likely to accumulate significant genetic damage over time and are therefore at high risk of becoming cancer cells (a process described later in this chapter). Cells targeted for apoptosis include many of the cells lining the digestive tract as well as those in the liver, two locations where cells are almost constantly in contact with harmful substances.
The rate at which mitosis occurs in animals varies dramatically for different types of cells. The most rapid cell division takes place in the bone marrow (as red blood cells are produced) and in the cells lining various tissues and organs.
The average red blood cell, for example, is in circulation for only about two to four months and then must be replaced ( FIGURE 6-11 ). The cells lining the intestines are replaced about every three weeks. Hair follicles, too, are among the most rapidly dividing cells.
Apoptosis
The pre-planned process of cell suicide
Certain cells are targeted for apoptosis

6. Overview: mitosis leads to duplicate cells.
For mitosis to begin, the parent cell replicates its DNA, creating a duplicate copy of each chromosome. Once this task is completed, mitosis can take place. Mitosis occurs in just four steps, in which the now-duplicated chromosomes are separated into identical sets in two separate nuclei, after which the cytoplasm and the rest of the cell are divided into two cells that pinch apart ( FIGURE 6-12 ) 6

7. Interphase: In Preparation for Mitosis, the Chromosomes Replicate
Mitosis is a four-step process
Interphase: In Preparation for Mitosis, the Chromosomes Replicate
Processes essential to cell division take place even before the mitotic phase of the cell cycle begins. During the DNA synthesis part of interphase, sister chromatids are formed as every chromosome replicates itself. Each pair of sister chromatids is held together at a centromere.  7

8. During which phase from the figure shown does the DNA replicate?
G1 phase
M phase
G2 phase
C phase
S phase M M A P T C G2
Ans:S
Interphase (G1, S, G2 phases)
Mitosis (M)
Cytokinesis (C) G1 S

9. Replication of chromosomes which happen during the S phase of interphase
Before mitosis begins, two important events occur.
1. The chromosomes replicate, becoming two identical linear DNA molecules. The two DNA molecules are held together at a region called the centromere. Throughout mitosis, until the centromere splits, each of the identical DNA molecules is called a chromatid; together, the two are called sister chromatids.
2. The sister chromatids begin the process of condensation, in which they coil tightly and become compact—in contrast to the uncondensed and tangled state of the chromosomes prior to replication, during most of interphase.

10. Mitosis The actual process of cell division occurs in four steps ( FIGURE 6-15 ).
Prophase: following replication, the sister chromatids condense. Prophase begins when the sister chromatids have condensed sufficiently to be seen with a light microscope. At this point, the spindle forms and the nuclear envelope breaks down.
2. Metaphase: the chromatids congregate at the cell center. After condensing, the pairs of sister chromatids seem to move aimlessly around the cell, but eventually they line up at the cell’s center, pulled by spindle fibers attached to a disk-like group of proteins, called a kinetochore, that develops on the centromere of each pair. At the end of metaphase, all the chromatid pairs are lined up in an orderly fashion, straddling the center in a “single-file” congregation that is called the metaphase plate. The chromatids are at their most condensed during this part of mitosis. 10

11. Current event: Mitosis New protein: BuGZ
The images show the microtubule-based spindle fibers (red), chromosomes (blue), and their kinetochores (green). Microtubules align chromosomes in the middle of the spindle in the presence of the newly discovered protein called BuGZ (+BuGZ), but mis-aligned in its absence (-BuGZ). Chromosome misalignment leads to its mis-segregation during cell division. Scale bar, 5 microns.
By looking beyond the microtubules and kinetochores themselves, Zheng's team identified a protein that regulates the interactions between the kinetochore and the microtubule fibers. Using super resolution microscopy, they were able to hone in on one particular phase of this process, namely the way that microtubules are "captured" by the kinetochore to promote proper alignment of the chromosomes in a way that facilitates equal partition of duplicated DNA.
Spindle fibers: red, chromosomes: blue, kinetochores: green

12. 3. Anaphase: the chromatids separate and move in opposite directions
3. Anaphase: the chromatids separate and move in opposite directions. In anaphase, the spindle microtubules attached to the centromeres begin pulling each chromatid in the sister chromatid pairs toward opposite poles of the cell. From each pair of sister chromatids, the centromere splits as one DNA molecule is pulled in one direction and the other, identical DNA molecule is pulled in the opposite direction. At the end of anaphase, one full set of chromosomes is at one end of the cell and another identical eventually occupy the nucleus of each of the two new daughter cells that result from the cell division.
4. Telophase: new nuclear membranes form around the two complete chromosome sets. With two full, identical sets of chromosomes collected at either end of the cell, the parent cell is prepared to divide into two genetically identical cells. In this last step, called telophase, the chromosomes begin to uncoil and fade from view, nuclear membranes reassemble, and the cell begins to divide into two.
The process of mitosis is generally accompanied by cytokinesis. 12

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14. Cytokinesis separation of the cytoplasm
(random assortment of organelles)
animal cells form a cleavage furrow
Cytokinesis: Animal Cells
plant cells form
a cell plate

15. If a parent cell which has 10 chromosomes, undergoes mitosis, each of the two daughter cells will have_______
Five chromosomes
Ten chromosomes
Twenty chromosomes
Ans:B

16. What happens if mitosis goes wrong?
Not equal number of chromosomes in the daughter cells (common in tumors)
Cell division out of control : Cancer !!!

17. Mitosis Review Occurs in somatic cells involves one nuclear division
Produces two ________ cells
Growth, tissue repair and asexual reproduction