Chapter 5: Cell Growth and Division



Chapter 5: Cell Growth and Division

Chapter Resources

Student Edition Labs

Mitosis in Onion Root Cells p. 143

Cancer p. 147

Options for Inquiry

Modeling Cell Surface Area-to-Volume Ratio p. 156

Apoptosis p. 157

Lab Binder

Additional Investigation: Animating Mitosis p. 37-39

Virtual Lab Worksheet. p. 84

Power Presentations

Presentation Chapter 5

Media Gallery

Stem Cells

Cell Cycle

Skin Cancer

Leaf Cross-section

Power Notes

Video

Clips on stem cells, cell growth, and cell division

Animated Biology

Mitosis

Binary Fission

Mitosis Stage Matching Game

Transparencies

The Cell Cycle T26

Chromosome Structure T27

Mitosis and Cytokinesis T28

Harvesting Embryonic Stem Cells T29



5.1: The Cell Cycle

Objectives: Describe the stages of the cell cycle.

Compare rates of division in different cell types.

Identify factors that limit cell size.

Warm Up: Why do you always have to cut your hair, your fingernails, and the lawn?

Words to Know: Cell Cycle, Mitosis, Cytokinesis

The Cell Cycle has Four Main Stages

• The Cell Cycle is the regular pattern of growth, DNA duplication, and cell division that occurs in eukaryotic cell.

• The Cell cycle is made up of 4 major stages:

• 1. Gap 1 (G1)

• 2. Synthesis (S)

• 3. Gap 2 (G2)

• 4. Mitosis.

• Gap 1, Synthesis, and Gap 2 make up Interphase.

Gap 1 (G1)

• During G1, a cell carries out its normal function.

• This includes growth, feeding and all other functions EXCEPT division.

Synthesis (S)

• Synthesis mean “the combining of parts to make a whole”.

• During the S stage, the cell makes a copy of its nuclear DNA.

• By the end of the S stage the nucleus of the cell contains 2 complete sets of DNA.

Gap 2 (G2)

• Cells continue to carry out their normal functions, and additional growth occurs.

• Everything must be in order by the end of G2 for division to continue.

Mitosis (M)

• Mitosis is the division of the cell nucleus and its contents.

• During mitosis, the nuclear membrane dissolves, the duplicated DNA condenses around proteins and separates and two new nuclei form.

• Cytokinesis is the process that divides the cell cytoplasm.

• The result is two daughter cell that are genetically identical to the original cell.

What might happen if the G2 checkpoint stopped working in cells?

Cells Divide at Different Rates

• Different types of cells divide at different rates.

• Some take more time, some less.

• Ex: Skin Cells live 2 weeks, Red blood cells live 4 months, Intestinal muscle cells live 16 years.

Do you think a skin cell would have a long or short G1 stage? Explain why.

Cell Size is Limited

• Cells have upper and lower size limits.

• If a cell is too big, it can not contain all the necessary organelles, if it is too big it does not have enough energy to live.

• The limit on cell growth is the ratio of cell surface area to volume.

• As a cell increases in size, its volume increases faster than its surface area and would not allow for exchange of needed materials.

Which has the larger ratio of surface area to volume, a tennis ball or a soccer ball? Explain your reasoning.

5.1 Assessment p. 137 (1-6)

5.2 Mitosis and Cytokinesis

Objectives: Describe the structure of a chromosome.

Follow chromosomes through the processes of mitosis and Cytokinesis.

Warm Up: What would you do if you had to put a lot of clothes into a small suitcase? If you were sharing it with someone else what would you have to do?

Words to Know: Chromosome, Histone, Chromatin, Chromatid, Centromere, Telomere, Prophase, Metaphase, Anaphase, Telophase.

Chromosomes Condense at the Start of Mitosis

• A Chromosome is one long continuous thread of DNA that consists of numerous genes along with regulatory information.

• Your body cells have 46 chromosomes each.

• If stretched out end to end one strand of DNA in your cells would be 3 meters long.

• DNA coils up and condenses so that it can fit in the nucleus of the cell.

• DNA wraps around proteins called histones that help compact the DNA.

• The loose combination of DNA and proteins is called Chromatin.

• One half of a duplicated chromosome is called a Chromatid. (two chromatids make a chromosome)

• Sister chromatids are held together in the middle by a Centromere.

What is the relationship between a molecule of DNA and a chromosome?

Mitosis and Cytokinesis Produce two Genetically Identical Daughter Cells.

Interphase

• This is the critical time for the duplication of organelle and for DNA replication.

• By the end of Interphase the cell has two completely identical sets of DNA.

Mitosis

• Mitosis divides a cell’s nucleus into two genetically identical nuclei, each with its own single, full set of DNA.

• This process occurs in ALL body cells (not sex cells).

• Mitosis occurs in 4 steps:

• 1. Prophase – chromatin condenses into tightly coiled chromosomes. Each chromosomes has two identical sister chromatids. The nuclear envelope breaks down, the nucleolus disappears, and the centrosomes and Centrioles begin to migrate to opposite sides of the cell. Spindle fibers begin to form.

• 2. Metaphase – the spindle fibers attach to the Centromere of each chromosome and align the chromosomes in the middle of the cell.

• 3. Anaphase – sister chromatids separate from each other when the spindle fibers begin to shorten. Chromatids move to opposite ends of the cell.

• 4. Telophase – a complete set of identical chromosomes is positioned at each pole of the cell. The nuclear membrane starts to form, the chromosomes begin to uncoil, and the spindle fibers fall apart.

Cytokinesis

• Cytokinesis divides the cytoplasm into two cells and completes a full stage of the cell cycle.

• In animal cell Cytokinesis, the membrane forms a furrow, or trench that is pulled inward.

• In plant cell Cytokinesis, a cell plate forms that allows for the cell wall to reform.

How does Cytokinesis differ in animal and plant cells?

5.2 Assessment p. 142 (1-4)

Mitosis in Onion Root Cells p. 143

5.3 Regulation of the Cell Cycle

Objectives: Identify internal and external factors that regulate cell division.

Explain cancer in terms of the cell cycle.

Warm Up: What is cancer?

Words to Know: Growth Factor, Apoptosis, Cancer, Benign, Malignant, Metastasize, Carcinogen

Internal and External Factors Regulate Cell Division

• Internal factors are in the cell.

• External factors are outside the cell.

External Factors

• These can be physical or chemical signals.

• Cell to cell contact is one example.

• Once a cell comes in contact with another cell, it stops dividing.

• Growth factors are a broad group of proteins that stimulate cell division.

• Hormones can also effect growth.

Internal Factors

• Two of the most important internal factors are kinases and cyclins.

• A kinase is an enzyme that helps controls the cell cycle.

• Cyclins are a group of proteins that are rapidly made and destroyed at certain points in the cell cycle.

Apoptosis

• Apoptosis is programmed cell death.

• It occurs when internal or external signals activate genes that help produce self-destructive enzymes.

• Ex: Human babies have webbing between their fingers and toes before birth.

• At a given time the cells are sent a signal that kills the cells making up the webbing.

• This is why most children are born without webbed toes and fingers.

Suppose a child was born whose receptors for growth hormone did not work properly. How do you think this would affect the child’s development?

Cell Division is Uncontrolled in Cancer

• Cancer is the common name for a class of diseases characterized by uncontrolled cell division.

• It occurs when the cell cycle breaks down.

• Cancer cell divide much more often than regular cells are required to.

• Cancer cells form disorganized clumps called tumors.

• In a Benign tumor, the cancer cells typically remain clustered together, are usually harmless, and can be removed.

• If a tumor is Malignant, some of the cancer cells can break away from the tumor and carried in the bloodstream or lymph to other parts of the body.

• This results in metastases, or spreading of the cancer throughout the body.

• A Carcinogen is a substance known to produce or promote the development of cancer.

• Ex: radiation, x-rays, tobacco smoke, air pollutants, even viruses.

• Standard cancer treatment often involves both radiation and chemotherapy.

• Radiation therapy is the use of radiation to kill cancer cells and shrink tumors.

• It damages the cell’s DNA so badly the cells no longer divide.

• Radiation is usually localized.

• Chemotherapy uses certain drugs, often in combination, to kill actively dividing cells.

• It will kill both healthy and cancerous cells.

• Unlike radiation the medication travels throughout the body and has stronger side effects.

HeLa cells are also used to study cell signaling processes. What might be a disadvantage of using cancer cells to study processes occurring in healthy cells?

5.3 Assessment p. 147 (105)

Quick Lab: Observing: Cancer p. 147

5.4: Asexual Reproduction

Objectives: Compare and contrast binary fission and mitosis.

Describe how some eukaryotes reproduce through mitosis.

Warm Up: Spider plants are common household plants which produce plantlets, or “babies” that can be removed, placed in soil, and will grow independently. Why can this form of reproduction be called asexual?

Words to Know: Asexual Reproduction, Binary Fission

Binary Fission is Similar in Function to Mitosis

• Asexual Reproduction is the creation of offspring from a single parent and does not involve the joining of gametes.

• The offspring that result are, for the most part, genetically identical to each other and to the single parent.

Binary Fission and Mitosis

• Binary Fission is the asexual reproduction of a single-celled organism by division into two roughly equal parts.

• Binary Fission and Mitosis have similar results.

• Both processes form 2 daughter cells.

• Both processes create 2 genetically identical cells.

• They are different in several ways:

• Bacteria have a single round DNA strand called a plasmid.

• Bacterial cells do not form a spindle.

• Bacterial cells do not have a nucleus.

• Binary Fission is a simpler process.

Advantages and Disadvantages of Asexual Reproduction

• Asexual reproduction can be more efficient than sexual.

• Asexual does not allow for genetic variation, sexual does.

Some Eukaryotes Reproduce through Mitosis

• Some eukaryotes reproduce asexually through mitosis.

• Budding – a small projection grows on the surface of the parent organism, forming a separate new individual.

• Fragmentation – a parent organism splits into pieces, each of which can grow into a new organism.

• Vegetative Propagation – involves the modification of a stem or underground structures of the parent organism.

How might the asexual reproduction of genetically identical plants be useful to humans? How could it prove harmful to our food supply?

5.4 Assessment p. 150 (1-5)

5.5: Multicellular Life

Objectives: Describe the specialization in multicellular organisms.

Identify different types of stem cells.

Warm Up: What are some of the different types of cells in your hand? Are the cells in the trunk of your body different?

Words to Know: Cell, Tissue, Organ, Organ System, Cell Differentiation, Stem Cell

Multicellular Organisms Depend on Interactions Among Different Cell Types

• Cells are the basic unit of structure and function for all living things.

• Tissues are a group of cells that work together to perform a similar task.

• Organs are a group of tissues that word together to perform a similar task.

• Organ Systems are groups of organs that carry out similar functions.

• Organism is any living thing.

• Ex: Heart cell ( Heart Tissue ( the Heart ( Circulatory System ( Human

Suppose your family goes out of town and forgets to ask your neighbor to water the plants. Do you think the plants’ stomata will be open or closed? Explain.

Specialized Cells Perform Specific Functions

• Cell Differentiation is the process by which unspecialized cells develop into their mature forms and functions.

• Ex: Skin cells only produce other skin cells. Heart cells only produce other heart cells.

Stem Cells Can Develop into Different Cell Types

• Stem cells are a unique type of body cell that have the ability to:

• 1. Divide and renew themselves for long periods of time.

• 2. Remain undifferentiated in form.

• 3. Develop into a variety of specialized cell types.

Stem Cell Classification

• Stem cells can be classified by their ability or potential to develop into the differentiated cell types of different tissues.

• Totipotent Stem Cells can grow into any other cell type. Only a fertilized egg and the cell produced by the first few divisions of an embryo are totipotent.

• Pluripotent Stem Cells can grow into any cell type except for totipotent stem cells.

• Multipotent Stem Cells can only grow into cells of a closely related cell family.

• Stem Cells can also be classified by their origin, as either adult or embryonic.

• Adult Stem Cells are partially undifferentiated cells located among the specialized cells of many organs and tissues.

• They are found in the brain, liver, bone marrow, skeletal muscle, dental pulp, and even fat.

• These are also found in children and in umbilical cord blood.

• The advantage to these cells is that they can be from the patient, grown in a culture and put back in the patient.

• The difficulty is they are difficult to isolate and tricky to grow.

• Embryonic Stem Cells come from donated embryos grown in a clinic.

• These embryos are the result of in vitro fertilization.

• These cells are taken from undifferentiated cells in the 3-5 day old embryos.

• These cells do not yet have instructions for what cells to become.

Research and Treatment Hope

• Stem cells have long been used to treat patients with leukemia and lymphoma.

• Stem cells are being studied to help treat diabetes and Parkensons disease.

• Human trials have just been approved by the FDA to test stem cells on Paraplegics to regenerate nerve cord tissue.

List treatment benefits and risks of both types of stem cells.

5.5 Assessment p. 155 (1-6)

Modeling a Cell Surface Area-to-Volume Ratio p. 156

Apoptosis investigation p. 157

Online Virtual Lab: Investigating Bacterial Growth

Animated Biology: Mitosis stages matching game.

Web Quest: Cancer

Interactive Review

Chapter Assessment p. 159-161

6.1: Chromosomes and Meiosis

Objectives: Differentiate between body cells and gametes.

Compare and contrast autosomes and sex chromosomes.

What makes sex cells different from all others, is it because they carry X and Y chromosomes? Explain.

Words to Know: Somatic Cell, Gamete, Homologous Chromosome, Autosome, Sex Chromosomes, Sexual Reproduction, Fertilization, Diploid, Haploid, Meiosis

You Have Body Cells and Gametes

• The two major types of cells in your body are Somatic Cells and Germ Cells.

• Somatic Cells (body cells) make up most of your body tissues and organs.

• Ex: spleen, kidneys, skin and eyes are all made of somatic cells.

• DNA in your body cells is NOT passed on to your children.

• Germ cells are cells in your reproductive organs (ovaries and testes) that develop into gametes.

• Gametes are sex cell (eggs and sperm).

• Each species has a characteristic number of chromosomes per cell.

• This number is for body cells, not gametes.

• Ex: Your body cells have 46 chromosomes, or 23 pairs of chromosomes.

• Ex: Your gamete cells have 23 chromosomes.

Which cell type makes up the brain?

Your Cells have Autosomes and Sex Chromosomes

• Your body cells have 23 pairs of chromosomes for a total of 46.

• These can be divided into two groups: 23 from mom and 23 from dad.

• Each pair of chromosomes is called a Homologous Pair.

• Homologous Chromosomes are two chromosomes that have the same length and general appearance.

• More importantly, the have copies of the SAME genes.

• Scientists have assigned a number to each pair.

• Pairs 1-22 are called Autosomes.

• Pair 23 is the Sex Chromosomes.

• These determine gender (male or female)

• XX = Female

• XY = Male (These are NOT homologous)

Are homologous chromosomes identical to each other? Explain

Body Cells are Diploid; Gametes are Haploid

• Sexual Reproduction involves the fusion of two gametes that results in offspring that are a genetic mixture of both parents.

• The actual fusion of sperm and egg is called Fertilization.

• These fuse to form a new nucleus with the correct number of chromosomes, one from each parent.

Diploid Cells

• Body cell and gametes have different numbers of chromosomes.

• Body (Somatic) cells are Diploid.

• Diploid means a cell has two copies of each chromosome (1 from mom, 1 from dad).

• Diploid is represented a 2n.

• In humans the diploid number is 46.

Haploid Cells

• Gametes are haploid.

• Haploid means that a cell has only one copy of each chromosome.

• Haploid is represented by n.

• In humans, egg and sperm cells the haploid number is 23.

• Maintaining the correct number of chromosomes is vital for healthy offspring.

• The exception is plants where you can have tetraploidy (4n).

Meiosis

• Meiosis is a form of nuclear division that divides a diploid cell into haploid cells.

• This process is essential for sexual reproduction.

• This process ensures that the offspring receives the correct number of chromosomes.

Why is it important that gametes are haploid cells?

6.1 Assessment p. 171 (1-5)

Data Analysis: Genetic Data p. 172

6.2 Process of Meiosis

Objectives: Compare and Contrast the two round of division in meiosis.

Describe how haploid cells develop into mature gametes.

Warm Up: In order to make 1 + 1 = 1, what needs to happen to the DNA of the parents?

Words to Know: Gametogenesis, Sperm, Egg, Polar Body

Cells go through Two Round of Division in Meiosis

• Meiosis is a form of nuclear division that creates four haploid cells from one diploid cell.

• Meiosis creates genetic diversity.

Homologous Chromosomes and Sister Chromatids

• Homologous chromosomes are two separate chromosomes: one from mom, one from dad.

• They are NOT copies of each other.

• Together the two chromosomes are called sister chromatids.

• Sister chromatids refer to the duplicated chromosomes that remain attached by the Centromere.

• Homologous chromosomes are divided in meiosis I. Sister Chromatids are divided in meiosis II.

Meiosis I

• Before Meiosis I begins, DNA has already been copied.

• Meiosis I divides homologous chromosomes.

• 1. Prophase I – nuclear membrane breaks down, centrosomes and Centrioles move to opposite sides of the cell and spindle fibers begin to form.

• 2. Metaphase I – Homologous chromosome pairs line up in the middle of the cell.

• 3. Anaphase I – paired homologous chromosomes separate from each other and move towards opposite ends of the cell.

• 4. Telophase I – nuclear membrane reforms in some species, spindle fibers disassemble and the cell undergoes Cytokinesis.

Meiosis II

• Meiosis II divides sister chromatids and results in undoubled chromosomes.

• DNA is NOT copied before this stage.

• 5. Prophase II – The nuclear membrane breaks down, centrosomes and Centrioles move to opposite side of the cell, spindle fibers form.

• 6. Metaphase II – Spindle fibers align the 23 chromosomes at the center of the cells. Each chromosome still has two sister chromatids.

• 7. Anaphase II – Sister chromatids are pulled apart and move to opposite ends of the cell.

• 8. Telophase II – Nuclear membranes form around each set of chromosomes and the cell undergoes Cytokinesis.

• The end result is four haploid cells.

Comparing Mitosis and Meiosis

|Mitosis |Meiosis |

|One cell division |Two cell divisions |

|Homologous chromosomes never pair up. |Homologous chromosomes line up at the equator. |

|Sister chromatids separate in anaphase. |In anaphase I sister chromatids remain together and homologous chromosomes |

| |separate. |

|Diploid Cells made. |Haploid cells made. |

|46 chromosomes |23 chromosomes |

|Somatic Cells |Sex cells |

What is the major difference between metaphase I and metaphase II?

Haploid Cells Develop into Mature Gametes

• Haploid cells are the end result of meiosis.

• Gametogenesis is the production of gametes.

• The sperm cell, the male gamete, is much smaller that the egg, the female gamete.

• Sperm formation starts with a round cell and ends by making a streamlined cell that can move rapidly.

• The formation of the egg is complicated.

• The end result is one egg and 3 polar bodies, cells with little more than DNA that are broken down.

Briefly explain how a sperm cell’s structure is related to its function.

6.2 Assessment p. 176 (105)

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