Cell Cycle and Mitosis
Cell cycle is the process that all body cells from multicellular organism use to grow and divide.
Starts when a cell has been produced by cell division and ends with the cell dividing to produce two identical cells.
Cell cycle consists of a period of cell growth and DNA replication called interphase and a period of cell division called mitosis.
Mitosis only occupies a small percentage of the cell cycle. Interphase takes up most of the cell cycle – 90%.
Interphase is divided into three separate growth stages called G1, S and G2. At G1 the cell grows and new organelles and proteins are made. Synthesis – The cell replicates its DNA and checks the DNA for errors or mutations that may have occurred. G2 – The cell keeps growing and proteins needed for cell division are made. During interphase the cell carries out normal functions but also prepares to divide. The cell’s DNA is unravelled and replicated to double its genetic content.
Form of cell division that occurs during the cell cycle. Needed for growth of multicellular organisms and repairing damaged tissues. It is a one continuous process but described in a series of division stages. Takes up 10% of the cell cycle.
Structure of Chromosomes in Mitosis:
The chromosomes are made up of two strands joined in the middle by a centromere. Separate strands are called chromatids. Two strands on the same chromosome are called sister chromatids. There are two strands due to each chromosome making an identical copy of itself during interphase.
Stages of Mitosis:
Prophase: chromosomes condense getting shorter and fatter. Centrioles start moving to opposite ends of the cell forming a network of spindle fibres. Nuclear envelope breaks down and chromosomes lie free in cytoplasm.
Metaphase: chromosomes (each with two chromatids) line up along the middle of cell at spindle equator and become attached to spindle by their centromere.
Anaphase: Centromeres divide, separating each pair of...