Interphase

Why do cells need to divide:

1.        To replace dead or damaged cells

2.        For growth of an organism

3.        For repair of a body tissue

4.        For reproduction eg. Production of gametes

Interphase: The longest stage of cell division (90% of cell cycle).The cell nucleus is visible. G1: Growth-cell growth, S: synthesis-DNA replication G2: preparation-organelles copied to prepare for cell division.

How is DNA packaged into proteins: DNA coils around histone proteins, called a nucleosome. The nucleosome coils into structures called chromatin. Chromatin super coiled into a chromosome.

Somatic cells: body cells 46 chromosomes

Gametes: sperm or eggs 23 chromosomes