Cell Growth and Division

The blue whale is the largest mammal in the world The blue whale is the largest mammal in the world. The pygmy shrew is one of he smallest mammals in the world. How does the size of an average cell compare between the two?

A. the average cell of a blue whale is smaller then the average cell of a pygmy shrew. B. the average cell of a blue whale is larger then the average cell of a pygmy shrew. C. the average cell of a blue whale is about the same size as the average cell of a pygmy shrew.

When an organism grows, the number of cells increase but the size of each cell remains small.

So if cells need to stay small, how does an organism get larger?

Division of the Cell When a cell gets too large, it : 1. makes a copy of its DNA (replication), and then… 2. divides to form two “daughter” cells.

The series of events that a cell goes through as it grows and divides is called the cell cycle.

Stages of the Cell Cycle Students can do manipulative during presentation

Preparation for Mitosis The Cell Cycle Cell Growth Cell Division DNA Replication Preparation for Mitosis

The Cell Cycle All the time in the cycle when the cell is NOT dividing is called interphase. Cells are in interphase 90% of the time

Preparation for Mitosis The Cell Cycle Cell Growth Cell Division DNA Replication Preparation for Mitosis

Interphase Interphase has three parts: G1, S, and G2. 1. G1 phase: cells grow. 2. S phase: DNA is replicated 3. G2 phase: organelles and molecules needed for cell division are made

Cell Division

Cell division is called the M phase. 1. Mitosis: Division of the cell nucleus 2. Cytokinesis: Division of the cell cytoplasm

Cell Division

Mitosis, the division of the cell nucleus, is made up of four segments: Prophase Metaphase Anaphase Telophase

M phase G2 phase S phase G1 phase

Controls on cell division Cell growth and cell division can be turned on and off. When you are injured your cells divide rapidly to repair the injury. When the injury has healed, the cells stop dividing.

Uncontrolled cell growth When cells in your body CANNOT control cell growth and division, cancer may form. Cancer cells cannot respond to the signals that regulate the division of cells. When cancer cells have been dividing uncontrollably, tumors form. Tumors can damage surrounding tissue. Cells from tumors can break free and travel to other parts of the body, forming new tumors.

Every somatic [body] cell in the puppy contains… (pick one) Eye Leg muscles Skin Every somatic [body] cell in the puppy contains… (pick one) A. equal number of mitochondria B. proteins that are all equal C. organelles for the synthesis of glucose D. identical genetic information

How does every cell in the body of the organism get the same genetic information? DNA replication

What do you remember about DNA replication? Review the DNA replication foldable

In which phase of the cell cycle does DNA replication take place? M phase G2 phase S phase G1 phase

Chromosomes are only visible during cell division, when they are condensed. The rest of the time the chromatin is spread throughout the nucleus.

Before cell division begins, each chromosome is replicated.

Phases of Mitosis [PMAT] Make foldable

Prophase 1. Chromosomes become visible (condensed) 2. Centrioles move to opposite ends of the nucleus. 3. Spindle fibers form between centrioles. 4. Nuclear envelope breaks down Centriole Spindle Fibers Students can create a foldable to take their notes for mitosis.

Metaphase 1. Chromosomes line up in the center of the cell 2. Spindle fibers attach to the centromere of each chromosome. Spindle Fibers attach to centromeres

Anaphase Sister chromatids separate from each other and are “pulled” to opposite ends of the cell.

This is the end of mitosis, but not the end of cell division. Telophase 1. Chromosomes look like threads (chromatin) again. 2. Nuclear envelope forms around each cluster of chromosomes 3. Spindle breaks apart Nuclear envelopes form This is the end of mitosis, but not the end of cell division.

Cytokinesis The cytoplasm divides. In plants, a cell plate forms between the two daughter nuclei. The cell plate develops into a cell membrane and cell wall.

Cytokinesis In animal cells, the cell membrane is drawn inward until the cytoplasm is pinched into two equal parts. The cleavage of daughter cells is almost complete; this is visualized by microtubule staining

What are some reasons that cells undergo mitosis? Growth Repair Maintenance Asexual reproduction

Review Questions

What are the structures shown What are the structures shown? How many copies of the cell’s DNA are shown here? A. Sister chromatids B. Centromere 2

? ? Phase Mitosis Cytokinesis ? ? ? ? Cell Cycle M Phase Interphase Prophase Metaphase Anaphase Telophase

What is the name of the structure labeled: Centriole Chromosome Spindle fiber

If your were to examine a sample of 1000 cells undergoing mitosis, in which of the phases listed below would you expect to find most of the cells? A. Prophase B. Metaphase C. Anaphase D. Telophase

When does the following occur? (Name the phase of the cell cycle. If it is in mitosis, name the phase of mitosis) 1. Sister chromatids separate. 2. Chromosomes line up across the center of the cell. 3. The cell’s DNA molecules are copied. 4. The cytoplasm pinches in half. 5. A spindle forms. Mitosis - Anaphase Mitosis - Metaphase S Phase Cytokinesis Mitosis - Prophase

What two labels would be most appropriate to replace the question marks in the figure above?

Cells grown in a petri dish will continue to grow until they come into contact with other cells. What would happen if the cells continued to divide?

What is a conclusion that could be drawn based on the above experiment What is a conclusion that could be drawn based on the above experiment? A. A substance in the cytoplasm of a dividing cell will stop the nucleus of the second cell from dividing. B. Adding a sample of cytoplasm will kill a cell. C. All cells begin mitosis at the same time. D. A substance in the cytoplasm of a dividing cell triggers the second cell to begin mitosis.

Based on the data, how are the consequences of injuries to the spinal cord and heart similar to each other? How are they different from the consequences of injuries to the smooth muscle? If cancer cells were added to the above table, predict what would be written in the “life span” and “cell division” columns. Explain.

What is cancer? Why is it sometimes called a disease of the cell cycle?

A scientist using a microscope observed several nuclei within the cytoplasm of a single cell. What process is probably not occurring if such cells have formed? Explain your answer.

Thousands of genetically identical trees have been discovered growing in a remote, undisturbed mountain area in Colorado. These trees are most likely the result of – A. genetic engineering B. asexual reproduction C. meiotic cell division D. biotechnology