Cell Division

Mitosis replaces worn-out old cells with fresh new duplicates

Generates ReplacementsCell divide to

a. Grow (increase in size)b. Repair (cells must be replaced with they die)c. Reproduction (new offsprings)

1. Asexual reproduction (one parent)2. Sexual reproduction (two parents

Each time a cell reproduces, the new cells contain all the essential cytoplasm, organelles, and chromosomes needed for an organism to develop, survive, and function.

CELL GROWTH

The cell cycle describes the series of phases that leads to

cell division

First Growth Phase

(G1)

Interphase – part of the cell cycle that occurs

between divisions G1, S, G2

G1: The cell’s primary growth phase. Normal cellular functions (making proteins, getting rid of waste, etc, take place.

2. Synthesis Replication

(S phase)

DNA is synthesis (S) –the

cell begins preparations

fordivision.

Every chromosome creates

an exact duplicate of itself in

a process called replication

Interphase – part of the cell cycle that occurs between divisions

Chromosome -compact X-shaped form of chromatin formed (and visible) during mitosis

Chromatid - single arm of an X-shaped chromosome

S- Synthesis/DNA Replication

Interphase part of the cell cycle that occurs between divisions (G1, S, and G2)

1. DNA appears like threadlike coils.

2. DNA coils to formChromosomes which appear as threadlike coils (chromatin) at start.

3. Chromosomes are copied (# doubles).

4. Sister chomatids at end of this phase

3. Second Growth Phase (G2)

Second period of growth and preparation for cell division

Interphase = G1 + S + G2

Interphase – part of the cell cycle that occurs between divisions

4. Mitosis - The cell’s nucleus duplicates, then divides

5. Cytokinesis Cytoplasm divides, forming two daughter cells

Mitosis Creates Duplicate Cells

Overview: Mitosis leads to

duplicate cells

Interphase

• Chromosomes condense

Mitosis - 1

• Chromosomes line up in the middle of the cell.

Mitosis 2

• Each chromosome is pulled away from its duplicate

Mitosis - 3

New membranes form around each complete set of chomosomes and the cell divides forming two new cells called daughter cells

Mitosis – 4

The Details: Mitosis is a four-step process

1 - Prophase

• Centrioles move to opposite poles of the cell

• Mitotic spindle, microtubules forms

• Chromosomes condense

• Nuclear envelope breakdown begins

Early Prophase

• Early prophase: chromosomes begin to condense and become visible.

Prophase: chromosomes are rod-shaped

• Sister chromatids line up at the center of the cell.

• Microtubules attach

sister chromatids to opposite poles of the spindle

2 - Metaphase

• Sister chromatids pairs are pulled apart by the spindle fibers. One full set of chomosomes goes to one side of the cell and another identical set goes to the other side.

3 - Anaphase

Anaphase: chromatids begin to separate and move away

• Spindle disperse

• Chromosomes are in opposite ends of the cell.

• Nuclear membrane forms around each set of chromatid

• Two new cells begin to form from the same parent.

4 - Telophase

Telophase: an envelop will arise around the daughter nuclei

Cytokinesis: Cytoplasm and organelles duplicate and are divided into equal parts. The cell splits in two

• Interphase is the time the cell spends between cell divisions, just doing its job in the body. Most of the time cells are in interphase.

Interphase

Mitosis - Stages

What stage of cell division is represented here?

What stage of cell division is represented here?

What stage of cell division is represented here?

What stage of cell division is represented here?

What stage of cell division is represented here?

What stage of cell division is represented here?

What stage of cell division does the cell

spend most of its time in?

What stage of cell division is represented by the cell at A?

What stage of cell division is represented by the cell at B?

What stage of cell division is represented by the cell at C?

What stage of cell division is represented by the cell at D?

What stage of cell division is represented by the cell at E?

What stage of cell division is represented here?

What stage of cell division is represented here?

What stage of cell division is represented here?

What stage of cell division is represented here?

What stage of cell division is represented here?

What stage of cell division is represented here?

What stage of cell division is represented here?

What structure is represented by A?

What cell organelle is found at A?

What term do we call the thread-like structures at B?

Meiosis I

Meiosos II

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Growth, Repair and Reproduction

Growth - is the result of cells producing new cells through cell division

• The number of cells making up the organism increases, and

• The organism grows.

• Chromosomes line up in the middle of the cell.

• Spindle fibers (microtubules) connect centrioles to chromosomes

3rd:Metaphase

Metaphase - chromosomes alined in central plane