Cell Division

The Cell Cycle:InterphaseMitosisCytokinesis

Cell Cycle

When a cell grows to a certain---predetermined size—it divides in to two cells.

One ‘parent’ cell divides into two ‘daughter’ cells

There are three main stages to this process.

Stage 1: Interphase

Period BEFORE cell division occurs. Cell grows to its mature stage. Cell makes a copy of its DNA

(chromosomes). Cell prepares to divide into two

cells.

Stage 1: Interphase-continued

Replication—this is when the DNA in the nucleus reproduces itself with an exact copy.

If the DNA (chromosomes) did not reproduce itself….then each new cell would only have ½ of the chromosomes it should have………

Stage 2: Mitosis

In this stage, one copy of the DNA (chromosomes) is distributed into each of the two new ‘daughter’ cells.

Prophase---Metaphase---Anaphase---Telophase

Stage 2: Mitosis--continued

Prophase: Chromosomes look like fishing line wrapped around a ball.

Each chromosome is made up of the doubled strand (chromatid) held together by a centromere.

Stage 2: Mitosis--continued

Metaphase: Chromosomes line up across the middle of the cell.

Each chromosome attaches to a spindle fiber that holds them together.

Stage 2: Mitosis--continued

Anaphase: The two chromatids of the Chromosome separate and each moves to the opposite end.

The cell appears stretched out.

Stage 2: Mitosis--continued

Telophase: The chromosomes begin to stretch out and lose their appearance.

A new nuclear membrane starts to appear and divides the nucleus into two different but identical nuclei.

Stage 3: Cytokinesis

This refers to when the cell membrane pinches in around the middle of the cell.

This separates the cell into two different but identical cells.

All organelles are evenly distributed to the new cells.

Stage 3: Cytokinesis-continued

Cytokinesis starts around the time of Telophase.

Structure of DNA

“double helix’ refers to a ladder that has sugars and phosphates

as the sides and nitrogen bases as the steps.