Cell Growth & Division Chapter 5. AKS Standards: 8b - describe the cell cycle; 9e - compare the advantages of sexual reproduction and asexual reproduction

Cell Growth & Division

Chapter 5

AKS Standards:

8b - describe the cell cycle;9e - compare the advantages of sexual reproduction and asexual

reproduction in different situations

Functions of Cell Division

1. Reproduction of cells all cells come from pre-existing cells results in two identical cells except for size

2. Growth and Development of Organisms

tadpoles become frogs, ivy vines get longer

3. Tissue renewal skin cells are being replaced, cuts and bruises heal

Stages of the Cell Cycle

During the cell cycle, a cell grows, prepares for division, and divides to form 2 identical daughter cells, where each one of which begins a new cycle.

The 5 phases of the cell cycle are:

1. Interphase (G1, S, G2) – period of rest between cell division

2. Prophase3. Metaphase4. Anaphase5. Telophase

6. Cytokinesis - division of the cytoplasm

phases of nuclear division (MITOSIS)

Events of the Cell Cycle

Gap 1 (G1): Cell carries out normal functions. It also increases in size and organelles increase in number.

Synthesis (S): Cell makes a copy of nuclear DNA.

Gap 2 (G2): Cells continue to carry out normal functions and prepares for Mitosis.

Mitosis (M): Includes nuclear division and cytokinesis.

Cells Divide at Different Rates

Rates of cell division vary widely, and each is linked to a body’s need for those cells:

Limits to Cell Size

Cells have upper and lower size limits. If they were too small, they could not contain all of

the necessary organelles and molecules. For example, a cell with only a few mitochondria

would not have enough energy to live. If they were too big, necessary nutrients and wastes

could not be transported efficiently into and out of cells.

For example, wastes would collect inside the cell and poison it; and nutrients could not reach organelles in a timely manner, so cells would die.

Also, information overload would occur. DNA makes copies as a cell divides, and there must be enough DNA blueprint to allow for protein production.

Review | Critical Thinking Activities

The following activities are highly recommended by your teacher. Each activity will allow you to (1) review main concepts; (2) apply what you have learned; and (3) think critically and analytically in such a way that allows you to form your own conclusions in novel applications: Section 5.1 Assessment Questions (textbook pp. 137). Section 5.1 Concept Map: The Cell Cycle – accessed via

the virtual textbook at classzone.com. Section 5.1 Virtual Quiz - accessed via the virtual

textbook at classzone.com.

AKS Standards:



Cell Division: Distributing Identical Sets of Chromosomes to Daughter Cells

Cell division is the copying and equal separation of chromosomes.

Chromosomes are long continuous threads of DNA that consists of numerous genes along with regulatory information: made up of DNA and protein cells of every organism have a

specific number of chromosomes not visible in cells except during cell

division

Chromosome Structure

Diploid v. Haploid Cells

HAPLOID CELLS - gametes

(single set of chromosomes)

DIPLOID CELLS - offspring

(full set of chromosomes)

Cell Division

Before it becomes too large, a growing somatic cell divides forming 2 “daughter” cells by a process known as cell division: The combined processes of mitosis

and cytokinesis produce two genetically identical daughter cells.

Each daughter cell gets 1 complete set of genetic information during cell division and therefore will be IDENTICAL TO THE MOTHER CELL!

A somatic cell is a non sex cell!

Review: Events of the Cell CycleInterphase is divided into 3 phases:

1. G1 – cell growth2. S – DNA replication3. G2 – preparation for Mitosis

During Interphase, chromosomes are in their “uncondensed” form and are called chromatin

Mitosis (nuclear division) is the division of the nucleus and it occurs in 4 phases:

1. P = prophase – chromatin condenses into chromosomes, the centrioles separate & nuclear membrane breaks down

2. M = metaphase – chromosomes line up across center of cell and each chromosome is connected to a spindle fiber at its centromere

3. A = anaphase – sister chromatids separate into individual chromosomes and are pulled apart

4. T = telophase – chromosomes gather at opposite ends of the cell and 2 new nuclear membranes form around them

Cytokinesis – division of cytoplasm

INTERPHASE

• Nucleus well defined bounded by nuclear envelope.

• Easily identifiable nucleolus.

• Genetic material in uncondensed form of chromatin – chromosomes cannot be seen.

Interphase is very long (cells spend most of time here):

G1 phase – cell growth; cells increase in size and synthesize new proteins and organelles

S phase – chromosomes are replicated and the synthesis of DNA molecules takes place; key proteins associated with the chromosomes are synthesized during this time

G2 phase – shortest of 3 phases; many of the organelles and molecules required for cell division are produced

M phase: Mitosis - PMAT

Nuclear Division (Mitosis) is divided into four phases: Prophase Metaphase Anaphase Telophase

USEFUL ANIMATION: http://www.sumanasinc.com/webcontent/animations/

content/mitosis.html

PROPHASE

• Chromatin coils and condenses; becomes visible as chromosomes.

• Centrioles separate and take up positions on opposite sides of the nucleus.

• Chromosomes become attached to spindle fibers.• Nucleolus disappears, nuclear membrane breaks down

Chromosome Duplication and Distribution During Mitosis

A duplicating chromosome consists of 2 sister chromatids, which narrow at their centromeres. The DNA molecules of sister chromatids are identical.

Chromosomes normally exist in the highly condensed state shown here only during the process of mitosis.

METAPHASE

• This is the shortest phase of mitosis. • Chromosomes line up in center of cell along metaphase plate.• For each chromosome, the kinetochores of the sister

chromatids are attached to microtubules coming from opposite poles of the cell.

ANAPHASE

• Anaphase begins suddenly when the paired centromeres that join the sister chromatids separate from each other.

• NOW EACH CHROMATID IS A SEPARATE CHROMOSOME….they begin moving toward opposite poles of the cell.

• Chromosomes continue to move until they have separated into two groups near the poles of the spindle.

• Anaphase is over when the chromosomes stop moving!

TELOPHASE

• Two daughter nuclei form at the two poles of the cell.• Chromosomes begin to relax back down into chromatin.• Nuclear envelope re-forms around each cluster of

chromatin.• Spindle begins to break apart and nucleolus reappears in

each daughter cell.• NUCLEAR DIVISION IS NOW COMPLETE, BUT NOT

CELL DIVISION!

Phases of Mitosis

Cytokinesis

Cytokinesis is the division of the cytoplasm itself. It can take place in a number of ways:

In animal cells – “draw-string” effect forms cleavage furrow (which pinches the cell into two parts).

In plant cells – cell plate forms from inside out, and cell wall begins to appear .

Cytokinesis in Animal and Plant Cells

The stages of Mitotic Cell Division in an Animal Cell: G2 phase; Prophase; Prometaphase

The Stages of Mitotic Cell Division in an Animal Cell: Metaphase; Anaphase; Telophase and Cytokinesis.


The following activities are highly recommended by your teacher. Each activity will allow you to (1) review main concepts; (2) apply what you have learned; and (3) think critically and analytically in such a way that allows you to form your own conclusions in novel applications: Section 5.2 Assessment Questions (textbook pp. 142). Animated Biology Activity: Mitosis Stage Matching Game

– accessed via the virtual textbook. Section 5.2 Concept Map: Mitosis – accessed via the

virtual textbook at classzone.com. Section 5.2 Virtual Quiz - accessed via the virtual


AKS Standards:



Regulation of the Cell Cycle

Cell cycle regulation is necessary for healthy growth.

Cell growth and division are regulated by both external factors, such as hormones and growth factors, and internal factors, such as proteins known as cyclins and kinases.

When proper regulated of cell growth is disrupted, a cell may become cancerous.

Cancer cells grow more rapidly than do normal cells and form clumps called tumors that may metastasize to other regions of the body.

Cell Division is Uncontrolled in Cancer

Cancer is a common name for a class if diseases characterized by uncontrolled cell division.

Cancer cells form disorganized clumps called tumors.

Cancer cells come from normal cells that have suffered damage to the genes that help make proteins involved in cell-cycle regulation.

These mutations may be inherited, or they may be caused by carcinogens (substances known to produce or promote the development of cancer).


The following activities are highly recommended by your teacher. Each activity will allow you to (1) review main concepts; (2) apply what you have learned; and (3) think critically and analytically in such a way that allows you to form your own conclusions in novel applications: Section 5.3 Assessment Questions (textbook pp. 147). WebQuest: Skin Cancer– accessed via the virtual

textbook. Section 5.3 Concept Map: Cell Cycle Regulation –

accessed via the virtual textbook at classzone.com. Section 5.3 Virtual Quiz - accessed via the virtual


AKS Standards:



Asexual Reproduction

Many organisms reproduce by cell division.

Most prokaryotes reproduce through a process known as binary fission, in which a cell divides into two approximately equal parts.

This is a type of asexual reproduction whereby the offspring are genetically identical to the parent organism, except when mutation occurs.


The following activities are highly recommended by your teacher. Each activity will allow you to (1) review main concepts; (2) apply what you have learned; and (3) think critically and analytically in such a way that allows you to form your own conclusions in novel applications: Section 5.4 Assessment Questions (textbook pp. 150). Virtual Lab: Investigating Bacterial Growth – accessed via

the virtual textbook. Section 5.4 Concept Map: Asexual Reproduction –

accessed via the virtual textbook at classzone.com. Section 5.4 Virtual Quiz - accessed via the virtual


AKS Standards:



Multicellular Life

Cell Differentiation

Stem Cells


The following activities are highly recommended by your teacher. Each activity will allow you to (1) review main concepts; (2) apply what you have learned; and (3) think critically and analytically in such a way that allows you to form your own conclusions in novel applications: Section 5.5 Assessment Questions (textbook pp. 155). Section 5.5 Concept Map: Multicellular Life – accessed

via the virtual textbook at classzone.com. Section 5.5 Virtual Quiz - accessed via the virtual

textbook at classzone.com. Reviewing Vocabulary & Main Ideas (textbook pp. 159).

Critical Thinking & Connecting Concepts (textbook pp. 160)

GEORGIA Standards-Based Assessment (textbook pp. 161).

Documents

Cell Growth & Division Chapter 5. AKS Standards: 8b - describe the cell cycle; 9e - compare the advantages of sexual reproduction and asexual reproduction