This chapter provides knowledge of cell cycle. The main contents of this chapter include all of the following: List the phases of the cell cycle and describe the key events of each phase, describe the process of DNA replication. | 3 Cells: The Living Units: Part D Cell Cycle Defines changes from formation of the cell until it reproduces Includes: Interphase Cell division (mitotic phase) Interphase Period from cell formation to cell division Nuclear material called chromatin Four subphases: G1 (gap 1)—vigorous growth and metabolism G0—gap phase in cells that permanently cease dividing S (synthetic)—DNA replication G2 (gap 2)—preparation for division Figure G1 Growth S Growth and DNA synthesis G2 Growth and final preparations for division M G2 checkpoint G1 checkpoint (restriction point) Figure Centrosomes (each has 2 centrioles) Nucleolus Interphase Plasma membrane Nuclear envelope Chromatin Interphase DNA Replication DNA helices begin unwinding from the nucleosomes Helicase untwists the double helix and exposes complementary chains The Y-shaped site of replication is the replication fork Each nucleotide strand serves as a template for building a new complementary strand DNA Replication DNA polymerase only works in one direction Continuous leading strand is synthesized Discontinuous lagging strand is synthesized in segments DNA ligase splices together short segments of discontinuous strand DNA Replication End result: two DNA molecules formed from the original This process is called semiconservative replication Figure Adenine Thymine Cytosine Guanine Old (template) strand Two new strands (leading and lagging) synthesized in opposite directions DNA polymerase DNA polymerase Lagging strand Leading strand Free nucleotides Old strand acts as a template for synthesis of new strand Chromosome Helicase unwinds the double helix and exposes the bases Old DNA Replication fork | 3 Cells: The Living Units: Part D Cell Cycle Defines changes from formation of the cell until it reproduces Includes: Interphase Cell division (mitotic phase) Interphase Period from cell formation to cell division Nuclear material called chromatin Four subphases: G1 (gap 1)—vigorous growth and metabolism G0—gap phase in cells that permanently cease dividing S (synthetic)—DNA replication G2 (gap 2)—preparation for division Figure G1 Growth S Growth and DNA synthesis G2 Growth and final preparations for division M G2 checkpoint G1 checkpoint (restriction point) Figure Centrosomes (each has 2 centrioles) Nucleolus Interphase Plasma membrane Nuclear envelope Chromatin Interphase DNA Replication DNA helices begin unwinding from the nucleosomes Helicase untwists the double helix and exposes complementary chains The Y-shaped site of replication is the replication fork Each nucleotide strand serves as a template for building a new complementary strand DNA Replication DNA polymerase only works in one direction Continuous leading strand is synthesized Discontinuous lagging strand is synthesized in segments DNA ligase splices together short segments of discontinuous strand DNA Replication End result: two DNA molecules formed from the original This process is called semiconservative replication Figure Adenine Thymine Cytosine Guanine Old (template) strand Two new strands (leading and lagging) synthesized in opposite directions DNA polymerase DNA polymerase Lagging strand Leading strand Free nucleotides Old strand acts as a template for synthesis of new strand Chromosome Helicase unwinds the double helix and exposes the bases Old DNA Replication .
