the Cell Cycle

http://protist.i.hosei.ac.jp/pdb/Images/Sarcodina/Heliozoa/Actinosphaerium/cell_division_1.jpg

Cell Division

• Cell division is the process where a cell divides to form 2 identical daughter cells

• It occurs as part of the cell cycle• Cell division is done for the purposes of:

reproduction, growth and repair

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Cell Division in Multicellular and Unicellular Organisms

• In unicellular organisms, cell division results in many new member that are identical to one another through a process called binary fission

• In multicellular organisms, cell division helps in the organisms’ development and the repair and renewal of cells

Cell Division of DNA

• The process of making new cells continues everyday to replace dead and damaged cells

• This occurs in somatic cells (body cells or non-sex cells) as oppose to gametes (sex cells)

• The process of cell division in somatic cells requires duplicating and separating the DNA, this is called mitosis

The Genome

• The genome is the all of the cell’s genetic information packaged into DNA

• Chromosomes are organized packages of DNA (humans have 46 chromosomes)

• DNA are the molecules that contain the genetic codes and instructions of our bodies

http://www.accessexcellence.org/RC/VL/GG/images/http://www.genome.gov/Glossary/resources/chromosome_lg_adv.jpg

Chromosomes

• A duplicated chromosome is made of 2 sister chromatids (identical copies of the chromosome’s DNA)

• The region where the strands connect is called the centromere

• During synthesis in the cell cycle , the chromosomes are duplicated, to allow for identical genetic information for the new cells

http://home.comcast.net/~clupold96/images/notes/chromosomes/chromosome_labeled.gif

http://www.uic.edu/classes/bios/bios100/lecturesf04am/realchromo.jpg

The Cell Cycle

• Interphase - includes 3 subphases• G1 phase - “First Gap” - growth• S phase - “Synthesis” - chromosome

duplication

• G2 phase - “Second Gap” - completes preparation for cell division

• M phase - mitosis and cytokinesis (splitting of cytoplasm)

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Interphase

• Interphase - the cell duplicates organelles and chromosomes and prepares cell for division

• This process takes up 90% of the cell cycle

Subphases

• First Gap - G1: Cellular contents are duplicated (not the chromosomes)

• Synthesis: chromosomes are duplicated• Second Gap - G2: The cell “double checks”

the duplicated chromosomes for error, makes repairs as needed

• G0 - cell cycle stops

Mitosis• The mitotic phase alternates with the much

longer interphase

• chromosomes line up in the middle of the nucleus

• they are pulled apart at the centromere• this separates them into 2 identical

chromatids

• 2 nuclei form around the chromosomes and the cell splits in half

http://geneticssuite.net/files/Mitosis.jpg