3.1 The Cell Cycle - prokaryotic cells

What are the four main events of cell division in all organisms?

• Cell Division Signals

• DNA Replication

• DNA segregation

• Cytokinesis

Cell Divison Signals for Prokaryotes

• Signals required to initiate cell divison

• Often external factors such as nutrient concentration and environmental conditions

What kind of factors control cell division?

• controlled by both external and internal signals

•  External signals come from the cell's environment, like growth factors, hormones, and physical cues

• Internal signals are a system of checkpoints and molecules, including cyclins and cyclin-dependent kinases

Through what process do prokaryotes divide?

Binary Fission

Binary Fission

• Reproduction of a prokaryote by division of a cell into two identical progeny cells

Steps of Binary fission

• DNA replication

• DNA segregation

• Cytokinesis

DNA replication in binary fission

• Replication begins at the ori (standing for ori)

• Replication ends at the ter (termination site)

• Occurs as DNA moves through a protein replication complex

• The DNA replicates as the cell grows

• The two origins move apart as replication proceeds

How many chromosomes do most prokaryotes have?

• One chromosome, often circular but folded

• It has 2 regions, the ori and ter

Describe DNA segregation in Prokaryotes

• Ori regions move to opposite ends of the cell, segregating the daughter chromosomes

• requires energy

• proteins required for this step hydrolyze ATP as a source of energy

Cytokinesis in prokaryotes 

• The cell membrane pinches in and protein fibers start to form a ring

• New cell wall materials are synthesized, resulting in the separation of the two cells

How are cell division signals different in eukaryotes?

• Internal environmental conditions are often suitable for cell division,
  but division may not always occur

How is cell division different in eukaryotic cells?

• Eukaryotic cells have more than one chromosome

• Replication begins on many different origins on the chromosome

• Replication is limited to one part of the cells

How is DNA segregation different in Eukaryotic Cells?

• Mitosis separates the newly replicated chromosomes into two new nuclei

• One copy of each chromosome ends up in each daughter cell

How is cytokinesis different in eukaryotic cells?

• Proceeds differently in animal and plant cells (because plants have cell walls)