The Cell Cycle

The Cell Cycle Cell Cycle = A repeating sequence of cell growth and division during the life of a cell. Cell division in eukaryotes = more complex due to organelles and a nucleus.

Five Stages of the Cell Cycle Interphase: G1 - primary growth phase S – synthesis; DNA replicated G2 - secondary growth phase Mitotic phase M - mitosis C - cytokinesis

Cell Cycle

Interphase - G1 Stage 1st growth stage after cell division Cells mature by making more cytoplasm & organelles Cell carries on its normal metabolic activities

Two identical copies of DNA are made Interphase – S Stage Synthesis stage DNA (chromosomes) copied Two identical copies of DNA are made Original DNA

Keeping Cells Identical The instructions for making cell parts are encoded in the DNA, so each new cell must get a complete set of the DNA molecules

Eukaryotic Chromosomes All eukaryotic cells store genetic info in chromosomes Most eukaryotes have between 10 and 50 chromosomes in their body cells Human body cells have 46 chromosomes (23 pairs)

Eukaryotic Chromosomes Each chromosome is made of tightly coiled DNA Chromatin is the relaxed form of DNA in a cell’s nucleus DNA can only be seen when highly coiled in chromosomes Chromatin: the relaxed form of DNA in the cell’s nucleus

Chromosomes in Dividing Cells Duplicated chromosomes are called sister chromatids Sister chromatids are held together by the centromere Called Sister Chromatids

Sister Chromatids result from the S phase! After S Phase Before S Phase

Interphase – G2 Stage 2nd Growth Stage Cell prepares for division All cell structures needed for division are made (ex: centrioles) Additional organelles & proteins are made

Cells prepare for Division Cell Divides into Identical cells Sketch the Cell Cycle DNA Copied Cells prepare for Division Cells Mature Daughter Cells Cell Divides into Identical cells