After studying this chapter, you should be able to accomplish the following outcomes: List the four stages of interphase, and describe the major events that occur during each stage in preparation for cell division; describe the difference between mitosis and cytokinesis; list the checkpoints that regulate the progression of cells through the cell cycle;. | The Cell Cycle and Cellular Reproduction Chapter 9 Bacterial Cell Division Bacteria divide by binary fission. -the single, circular bacterial chromosome is replicated -replication begins at the origin of replication and proceeds bidirectionally -new chromosomes are partitioned to opposite ends of the cell -a septum forms to divide the cell into 2 cells Eukaryotic Chromosomes Eukaryotic chromosomes – -linear chromsomes -every species has a different number of chromosomes -composed of chromatin – a complex of DNA and proteins -heterochromatin – not expressed -euchromatin – expressed regions Eukaryotic Chromosomes Chromosomes are very long and must be condensed to fit within the nucleus. -nucleosome – DNA wrapped around a core of 8 histone proteins -nucleosomes are spaced 200 nucleotides apart along the DNA -further coiling creates the 30-nm fiber or solenoid Eukaryotic Chromosomes The solenoid is further compacted: -radial loops are held in place by scaffold proteins -scaffold of proteins is aided by a complex of proteins called condensin karyotype: the particular array of chromosomes of an organism Eukaryotic Chromosomes Chromosomes must be replicated before cell division. -Replicated chromsomes are connected to each other at their kinetochores -cohesin – complex of proteins holding replicated chromosomes together -sister chromatids: 2 copies of the chromosome within the replicated chromosome Eukaryotic Cell Cycle The eukaryotic cell cycle has 5 main phases: 1. G1 (gap phase 1) 2. S (synthesis) 3. G2 (gap phase 2) 4. M (mitosis) 5. C (cytokinesis) The length of a complete cell cycle varies greatly among cell types. interphase Interphase Interphase is composed of: G1 (gap phase 1) – time of cell growth S phase – synthesis of DNA (DNA replication) - 2 sister chromatids are produced G2 (gap phase 2) – chromosomes condense Interphase Following S phase, the sister chromatids appear to share a centromere. In fact, the . | The Cell Cycle and Cellular Reproduction Chapter 9 Bacterial Cell Division Bacteria divide by binary fission. -the single, circular bacterial chromosome is replicated -replication begins at the origin of replication and proceeds bidirectionally -new chromosomes are partitioned to opposite ends of the cell -a septum forms to divide the cell into 2 cells Eukaryotic Chromosomes Eukaryotic chromosomes – -linear chromsomes -every species has a different number of chromosomes -composed of chromatin – a complex of DNA and proteins -heterochromatin – not expressed -euchromatin – expressed regions Eukaryotic Chromosomes Chromosomes are very long and must be condensed to fit within the nucleus. -nucleosome – DNA wrapped around a core of 8 histone proteins -nucleosomes are spaced 200 nucleotides apart along the DNA -further coiling creates the 30-nm fiber or solenoid Eukaryotic Chromosomes The solenoid is further compacted: -radial loops are held in place by scaffold proteins
