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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.
PowerPoint® Lecture Slides prepared by Janice Meeking, Mount Royal College CHAPTER Cells: The Living Units: Part D Copyright © 2010 Pearson Education, Inc Cell Cycle • Defines changes from formation of the cell until it reproduces • Includes: • Interphase Cell division (mitotic phase) Copyright â 2010 Pearson Education, Inc 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 Copyright © 2010 Pearson Education, Inc G1 checkpoint (restriction point) S Growth and DNA synthesis G1 Growth M G2 Growth and final preparations for division G2 checkpoint Copyright © 2010 Pearson Education, Inc Figure 3.31 Interphase Centrosomes (each has centrioles) Nucleolus Interphase Copyright © 2010 Pearson Education, Inc Nuclear envelope Plasma membrane Chromatin Figure 3.33 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 Copyright © 2010 Pearson Education, Inc 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 Copyright © 2010 Pearson Education, Inc DNA Replication • End result: two DNA molecules formed from the original • This process is called semiconservative replication Copyright © 2010 Pearson Education, Inc Chromosome Free nucleotides DNA polymerase Old strand acts as a template for synthesis of new strand Leading strand Old DNA Helicase unwinds the double helix and exposes the bases Replication fork Adenine Thymine Cytosine Guanine Copyright © 2010 Pearson Education, Inc Two new strands (leading and lagging) synthesized in opposite directions Lagging strand DNA polymerase Old (template) strand Figure 3.32 ... 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 Copyright... Chromosome Free nucleotides DNA polymerase Old strand acts as a template for synthesis of new strand Leading strand Old DNA Helicase unwinds the double helix and exposes the bases Replication fork Adenine... © 2010 Pearson Education, Inc Two new strands (leading and lagging) synthesized in opposite directions Lagging strand DNA polymerase Old (template) strand Figure 3.32