Biology - The Cell Cycle and why its important

Why do cells divide?

1. Reproduce
2. Grow
3. Repair damage

Asexual reproduction

The process of producing an offspring from only one parent. The offspring is an exact genetic variety.

Disadvatages of asxeual reproduction

No genetic variety

Sexual reproduction

the process of producing offspring by the fusion of two gametes (half-cells). The offspring inherits characteristics from each parent.

Diffusion

The movement of dissolved substances from an area of higher concentration to an area of lower concentration until they are equal.

Osmosis

The movement of water across a cell membrane from an area of higher concentration to an area of lower concentration until they are equal.

Chromosome

Condensed DNA

Chromatin

Uncondensed DNA

Where does cell division take place?

Nucleus

Sister chromatids

A chromosome consisting of two identical strands connected at a centromere.

The cell cycles' three stages

Interphase
Mitosis
Cytokinesis

Interphase

The longest phase.
Has 3 stages:
G1 - Rapid growth in size
S - DNA is replicated. (The chromosomes double)
G2 - Slow growth, preparing for cell division

What are the stages in Mitosis?

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

Prophase

1. Chromosomes condesnse and become visible
2. Nucleus disappears, nuclear membrane breaks down
3. Centrioles begin to move to cell poles

Metaphase

1. Spindle fibres connect to chromosomes
2. Chromosomes line up along the equator of the cell

Anaphase

1. the centromere splits and sister chromatids separate into daughter chromosomes
2. They appear to be pulled apart

Telophase

1. The daughter chromosomes stretch out and become thinner
2. A nuclear membrane reforms around the chromosomes at each end of the cell

Cytokinesis

The cutoplasm divides forming two daughter cells

Cytokinesis in animal cell

The new cell membrane pinches together at the center

Cytokinesis in plant cells

A cell plate forms at the equator and becomes the new cell wall

In which phase are chromosmes located at the equator of the cell?

Metaphase

When are the spindle fibres formed?

Prophase

In which phase are chromosomes not visible in?

Interphase