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B-2.6 Summarize the characteristics of the cell cycle: interphase
(called G1, S, G2); the phases of mitosis (called prophase,
metaphase, anaphase, and telophase); and plant and animal
cytokinesis.
What you should know:
Cell cycle has 4 stages prior to division:
G1 – first growth – young cell grows
S – synthesis – DNA doubles
G2 – second growth – prepares for division
M – cell division – either mitosis or meiosis
Interphase
 Cells spend the majority of their cell cycle in interphase.
○ Interphase includes the first 3 phases of the cell cycle:
 During synthesis, when DNA doubles, sister chromatids are formed:
Mitosis
 Asexual Reproduction
 Creates 2 identical cells with the diploid # of chromosomes (in humans = 46)
○ Mitosis has four phases:
Cytokinesis
Cytokinesis is the division of the cytoplasm at the end of mitosis
 In animal cells - forms a cleavage furrow that pinches the cell in two
 In plant cells – forms a cell plate down the middle
Animal Cell Telophase/Cytokinesis
Plant Cell Telophase/Cytokinesis
What they might ask:
 identify a specific description or diagram as a particular phase of the cell cycle;
 compare the phases of the cell cycle and mitosis;
B-2.7
Summarize how cell regulation controls and coordinates
cell growth and division and allows cells to respond to the
environment, and recognize the consequences of uncontrolled cell
division.
What you should know: .
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the cell cycle is driven by a chemical control system
Cells respond to chemical signals:
○ An internal signal – enzymes inside the cell
○ An external signal - growth factor outside the cell
Cells respond to physical signals from their environment:
○ Cells sense when they are too closely packed and cell division is turned off.
○ Cells sense when they are not in contact with a surface and cell division is turned on.
Uncontrolled cell division leads to Cancer
Cancer cells continue to divide even when they are very densely packed and/or there is no
growth factor present.
○ Cancer begins when a single cell changes into a cancer cell
○ If a mass of these cells that invades and impairs the functions of one or more organs it is
called a malignant tumor.
○ If the mass of abnormal cells remains at the original site it is called a benign tumor.
Cancer cells can separate from the original tumor, enter the blood and lymph vessels of the
circulatory system, and invade other parts of the body, where they grow to form new tumors.
What they might ask:
recall that a breakdown in the cellular regulatory process can result in growth of tumors.
B-4.5
Summarize the characteristics of the phases of meiosis I
and II.
Meiosis
 Sexual Reproduction
 Creates 4 different cells with the haploid # of chromosomes (in humans = 23)
 Because the haploid cells (gametes) have only half the chromosomes, they must join together
to form a new diploid cell
 Increases genetic variety because combines DNA from two parents
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Meiosis occurs in 2 stages:
Meiosis I
A
prophase I
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B
metaphase I
C
anaphase I
D
telophase I
Prophase I (as in figure “A” above)
 Crossing over occurs as homologous chromosomes are close to each other, switch
pieces of chromosomes
Metaphase I (as in figure “B” above).
Anaphase I (as in figure “C” above)
Telophase I & Cytokinesis (as in figure “D” above)
Ends with 2 diploid cells, but chromosomes still in sister chromatids
Meiosis II
(E)
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(F)
(G)
(H)
Starts with 2 cells from Meiosis I
Prophase II (as in figure “E” above)
Metaphase II (as in figure “F” above)
Anaphase II (as in figure “G” above)
Telophase II & Cytokinesis (as in figure “H” above)
Ends with 4 haploid cells – sperm in males or eggs in females
What they might ask:
 summarize the phases of meiosis I and meiosis II
 identify the phases of mitosis from scientific diagrams of the phases of meiosis;
 compare the processes and outcomes of meiosis I to meiosis II
 compare haploid cells to diploid cells;
 compare the processes and outcomes of mitosis and meiosis
 explain the effect of crossing over on the genetic variation in daughter cells.
B-2.4
Explain the process of cell differentiation as the basis for
the hierarchical organization of organisms (including cells,
tissues, organs, and organ systems).
What you should know:
 In the development of most multicellular organisms, a single cell (fertilized egg) gives rise to
many different types of cells, each with a different structure and function.
○ All cells in an organism have the same DNA
○ As cell division proceeds, the cells not only increase in number but differentiate and
become specialized in structure and function.
○ During the process of differentiation, only specific parts of the DNA are activated
○ The various types of cells (such as blood, muscle, or epithelial cells) arrange into tissues
which are organized into organs, and, ultimately, into organ systems.
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Stem cells are undifferentiated cells that continually reproduce themselves and could become
any type of cell
○ embryonic stem cells.
○ adult stem cells.
What they might ask:
 explain how cell differentiation results in the hierarchical organization of an organism
(including cells, tissues, organs, and organ systems)
 recall that all of the cells of a particular organism contain all of the genetic code for the
organism;
 summarize the unique characteristics of embryonic and adult stem cells;
 compare the results of cell division and cell differentiation.