Name	   Class 	   Date 	

10.1 Cell Growth, Division, and Reproduction
Lesson Objectives
•	Explain the problems that growth causes for cells.
•	Compare asexual and sexual reproduction.
Lesson Summary
Limits to Cell Size There are two main reasons why cells divide:
Information “overload”: The larger a cell gets, the more demands it places on its DNA. Eventually, the cell’s DNA cannot meet the cell’s needs.
Exchange of materials: Cells take in nutrients and eliminate wastes through the cell membrane.
•	The larger a cell’s volume, the more materials it needs to function and the more waste it creates.
•	A cell’s volume increases at a faster rate than its surface area. As a cell grows, its surface-area-to-volume ratio becomes too small.
•	The larger a cell gets, the harder it is for enough materials to move across its cell 
membrane.
Cell division solves the information overload and materials exchange problems.

Cell Division and Reproduction Cell division is part of both types of reproduction:
Asexual reproduction:
•	produces genetically identical organisms.
•	occurs in many single-celled organisms and in some multicellular organisms.
•	allows rapid reproduction of organisms in favorable environments.
Sexual Reproduction:
•	produces organisms with genetic information from both parents.
•	occurs in most animals and plants and in many single-celled organisms.
•	increases genetic diversity, which aids species survival in changing environments.

Limits to Cell Size
For Questions 1–4, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true.
	  1.   As a cell’s size increases, its amount of DNA also increases.
	  2.   The amount of activity in a cell is related to its volume.
	  3.   The smaller the cell, the smaller its ratio of surface area to volume.
	  4.   The information crisis in a cell is solved by the replication of the DNA before cell division.

5.	In the visual analogy of the growing town, what does the library represent? Identify two characteristics that make it a good choice for this analogy.

	
	
Cell Division and Reproduction
For Questions 6–8, complete each statement by writing the correct word or words.
6. 	 is the formation of new individuals.
7. For single-celled organisms, cell division is a form of 	 reproduction.
8. Most multicellular organisms reproduce by 	 reproduction.
9. Use the table to compare and contrast asexual and sexual reproduction.

Asexual and Sexual Reproduction	
Similarities	Differences	

10.2 The Process of Cell Division
Lesson Objectives
•	Describe the role of chromosomes in cell division.
•	Name the main events of the cell cycle.
•	Describe what happens during the four phases of mitosis.
•	Describe the process of cytokinesis.
Lesson Summary
Chromosomes Packages of DNA called chromosomes hold a cell’s genetic information.
Prokaryotic chromosomes consist of a single, circular strand of DNA.
Eukaryotic chromosomes are highly organized structures.
•	The DNA winds around histone proteins, forming chromatin.
•	Chromosomes make the precise separation of DNA possible during cell division.
The Cell Cycle The cell cycle is the series of events in the growth and division of a cell.
In the prokaryotic cell cycle, the cell grows, duplicates its DNA, and divides by pinching in the cell membrane.
The eukaryotic cell cycle has four stages (the first three of which are referred to as interphase):
•	In the G1 phase, the cell grows.
•	In the S phase, the cell replicates its DNA.
•	In the G2 phase, the cell produces organelles and materials for division.
•	In the M phase, the cell divides in two stages—mitosis, the division of the nucleus, and cytokinesis, the division of the cytoplasm.
Mitosis The division of the nucleus, mitosis, occurs in four stages:
Prophase : a cell’s genetic material condenses, a spindle starts to form, and the nuclear envelope breaks down.
Metaphase : the duplicated chromosomes line up and spindle fibers connect to the centromeres.
Anaphase : sister chromatids separate and move toward the centrioles.
Telophase : the chromosomes begin to unwind and a nuclear envelope reforms.
Cytokinesis Division of the cytoplasm differs in plant cells and animal cells.
In animal cells, the cell membrane draws in and pinches off. 
In plant cells, a cell plate forms, followed by a new cell membrane, and finally a new cell wall forms.

Chromosomes
For Questions 1–5, complete each statement by writing the correct word or words.
1. Cells carry genetic information in packages of DNA called 	.
2. Most 	 have only one circular strand of DNA.
3. In eukaryotic cells, the genetic structure consists of DNA and a tightly wound protein, which together form a substance called 	.
4. The beadlike structures formed by DNA wrapped around 	 molecules are called nucleosomes.
5. 	 make possible the precise separation of DNA during cell division.

The Cell Cycle
6. What is the name of the type of cell division that occurs in the prokaryotic cell cycle?
	
7. What happens during interphase?

8. Complete the cell cycle diagram by writing the correct name of a phase on each line. Briefly describe each phase  
     in the space next to the diagram.

9. In eukaryotic cells, what happens in the G1 phase that differs from the G2 phase?
	
10. In eukaryotic cells, what are the two main stages of cell division?

Mitosis
11. During prophase, when cell chromosomes become visible, what are the duplicated strands of DNA called? What is the name for the area in which these duplicated strands are joined?

12. What structures are spindle fibers attached to that help pull the paired chromosomes apart?

17. The four circles below represent the nucleus of a cell going through mitosis. Draw four chromosomes as they go through each phase. Label each phase and describe what is happening to the DNA.

Cytokinesis
18. What is cytokinesis?

	

19. For Questions 2–9, match the event with the phase of the cell cycle in which it takes place. A phase may be used more than once.
Event	Phase of the Cell Cycle

		2.  A nuclear envelope forms around chromosomes.
		3.  The cell grows and replicates DNA.
		4.  A spindle forms.
		5.  Chromosomes line up across the center of the cell.
		6.  The genetic material condenses and Chromosomes become visible.
		7.  Chromosomes move to opposite sides of the cell.
		8.  The cytoplasm divides.
		9.  Sister chromatids separate.

A.  anaphase
B.  cytokinesis
C.  interphase
D.  metaphase
E.  prophase
F.  telophase
10.3 Regulating the Cell Cycle
Lesson Objectives
•	Describe how the cell cycle is regulated.
•	Explain how cancer cells are different from other cells.
Lesson Summary
Controls on Cell Division Dozens of proteins regulate the cell cycle.
Cyclins are proteins that regulate the timing of the cell cycle in eukaryotic cells.
Regulatory proteins work both inside and outside of the cell.
•	Internal regulators allow the cell cycle to proceed when certain events have occurred within a cell.
•	External regulators called growth factors stimulate the cell cycle. Other external regulators cause the cell cycle to slow down or stop.
Apoptosis is programmed cell death that plays a key role in the development of tissues and organs.

Cancer: Uncontrolled Cell Growth Cancer is a disorder in which cells divide uncontrollably, forming a mass of cells called a tumor.
Cancers are caused by defects in genes that regulate cell growth.
Treatments for cancer include:
•	removal of cancerous tumors.
•	radiation, which interferes with the copying of DNA in multiplying cancer cells. 
•	chemotherapy, which is the use of chemicals to kill cancer cells.

Controls on Cell Division
For Questions 1–6, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true.
	   1.   Cells tend to continue dividing when they come into contact with other cells.
	   2.   Cell division speeds up when the healing process nears completion.
	   3.   Proteins called growth factors regulate the timing of the cell cycle in eukaryotic cells.
	   4.   If chromosomes have not attached to spindle fibers during metaphase, an internal regulatory protein will prevent the cell from entering anaphase.
	   5.   Growth factors are external regulatory proteins that slow down the cell cycle.
	   6.   Once apoptosis is triggered, a cell proceeds to self-destruct.

7. Complete the cause-and-effect chart by giving an example of an effect caused by each type of regulatory protein.

Factors Affecting the Cell Cycle	
Cause	Effect	
Cyclins		
Internal regulatory proteins		
External regulatory proteins		
Cancer: Uncontrolled Cell Growth
8. What is cancer?

9. What are the two basic types of tumors? Explain how they are different.

	

10. Why can cancer be life threatening?

	
	
11. What is the cause of cancer?
	
12. How do radiation and chemotherapy affect cancer cells?

10.4 Cell Differentiation
Lesson Objectives
•	Describe the process of differentiation.
•	Define stem cells and explain their importance.
•	Identify the possible benefits and issues relating to stem cell research.
Lesson Summary
From One Cell to Many Multicellular organisms produced via sexual reproduction begin life as a single cell.
Early cell divisions lead to the formation of an embryo.
Then, individual cells become specialized in both form and function through the process of differentiation.
Once cells of a certain type, such as nerve cells or muscle cells, have formed, the cells cannot develop into a different type of cell.

Stem Cells and Development During an organism’s development, some cells differentiate to become a wide variety of body cells.
A fertilized egg and the first few cells in an embryo are able to form any kind of cell and tissue. Such a cell is termed totipotent.
A blastocyst is an embryonic stage that consists of a hollow ball of cells. These cells are able to become any type of body cell. Such cells are termed pluripotent.
Unspecialized cells that can develop into differentiated cells are called stem cells. Stem cells are found in embryos and in adults.
•	Embryonic stem cells are the pluripotent cells of an early embryo.
•	Adult stem cells are multipotent, which means they can produce many, but not all, types of differentiated cells.

Frontiers in Stem Cell Research Scientists want to learn about the signals that tell a cell to become either specialized or multipotent.
Potential benefits of stem cell research include the repair or replacement of damaged cells and tissues.
Research with human stem cells is controversial because it involves ethical issues of life and death.

From One Cell to Many
For Questions 1–4, complete each statement by writing the correct word or words.
1. Humans, pets, and petunias all pass through an early stage of development called a(n) ___________.
2. Cells become 	 through the process of differentiation.
3. Scientists have mapped the outcome of every 	 that leads to differentiation in the development of the microscopic worm C. elegans.
4. Most cells in the adult body are no longer capable of 	.

Stem Cells and Development
For Questions 5–7, write the letter of the correct answer on the line at the left.
	   5.  Which is an example of a totipotent cell?
	A. blastocyst 			C. fertilized egg
	B. bone cell 			D. lymphocyte
	   6.  Cells that are pluripotent are unable to develop into the tissue that
	A. forms the skin. 			C. produces blood cells.
	B. lines the digestive tract. 	D. surrounds an embryo.	
	   7.  Adult stem cells are best described as
	A. multipotent. 			C. totipotent.
	B. pluripotent. 			D. unable to differentiate.	
8. Complete the concept map by identifying some of the types of cells that embryonic stem cells 	give rise to. Then explain how stem cells are like the stem of a plant.

		

Embryonic Stem Cells

can become

Frontiers in Stem Cell Research
For Questions 9–11, write the letter of the correct answer on the line at the left.
	     9.  Which is not a new, potential benefit of stem cell research?
A. growing new skin cells to repair a cut
B. replacing heart cells damaged by heart attacks
C. repairing breaks between nerve cells in spinal injuries
D. preventing suffering and death caused by cellular damage
	    10. What is the main reason that embryonic stem cell research is considered ethically controversial?
A. growing new skin cells to repair a cut
B. replacing heart cells damaged by heart attacks
C. repairing breaks between nerve cells in spinal injuries
D. preventing suffering and death caused by cellular damage
	    11. What is one new technology that could make stem cell research less controversial?
A. implanting skin cells instead of stem cells in damaged tissue
B. developing the ability to switch on the genes that make an adult cell pluripotent
C. replacing stem cells with cancer cells
D. using the Internet to get more people to accept stem cell research

Chapter 10 Vocabulary Review
1. Define the following terms:

asexual reproduction-
sexual reproduction -
chromosome-
binary fission-
mitosis-
meiosis- 
cytokinesis-
For Questions 2–9, match the event with the phase of the cell cycle in which it takes place. A phase may be used more than once.

Phase of the Cell Cycle 
A.  anaphase
B.  cytokinesis
C.  interphase
D.  metaphase
E.  prophase
F.  telophase

Event	

		2.  A nuclear envelope forms around chromosomes.
		3.  The cell grows and replicates DNA.
		4.  A spindle forms.
		5.  Chromosomes line up across the center of the cell.
		6.  The genetic material condenses and Chromosomes become visible.
		7.  Chromosomes move to opposite sides of the cell.
		8.  The cytoplasm divides.
		9.  Sister chromatids separate.