Cell Processes Mitosis and Meiosis

Cell Cycle The cell cycle is a regular sequence of growth and division that cells undergo.

Stage 1: Interphase Cells grow to its full size Make an exact copy of its DNA –DNA is found in chromatin Centrioles are also copied Prepare to divide into two cells

Stage 2: Mitosis Division of cytoplasm into two new (daughter) cells Mitosis is divided into 4 parts –Prophase –Metaphase –Anaphase –Telophase

The Cell Cycle Prophase- –chromatin condense to form chromosomes. –Pairs of centrioles move to opposite side of the nucleus. –Spindle fibers form a bridge between the ends of the cell. –The nuclear envelope breaks down.

The Cell Cycle Metaphase- –Chromosomes line up across the center of the cell. –Chromosome attaches to a spindle fiber at its centromere

The Cell Cycle Anaphase –Centromeres split. –The two chromatids separate and each chromatid becomes a new chromosome. –The new chromosome move to opposite ends. – The cell stretches out as the opposite ends are pushed apart.

The Cell Cycle Telophase –Chromosomes begin to stretch out and lose their rod-like appearance. –A new nuclear envelope forms around each region of the chromosomes Stage 3- Cytokinesis –The cytoplasm divides and the organelles are distributed into each of the two cells.

The Cell Cycle

DNA DNA has four kinds of nitrogen bases: –A (adenine) –T (thymine) –G (guanine) –C (cytosine) Only A and T pair Only G and C pair

The Replication Process DNA replication begins when the two sides of the DNA molecule unwind and separate, like a zipper unzipping. Next, nitrogen bases that are floating in the nucleus pair up with the bases on each half of the DNA molecule. Once the new bases are attached, a new DNA molecule had formed.