Ch. 12: The Cell Cycle

KEY CONCEPTS Cell division results in genetically

identical daughter cells The mitotic phase alternates with

interphase in the cell cycle The eukaryotic cell cycle is regulated

by a molecular control system

Key Roles of Cell Division Reproduce more of your own kind

R.Virchow in 1855 “Omnis cellula e cellula” (Every cell comes from a cell)

Amoeba or plant cuttings Physically pass a copy of the ‘information’ on

to the next generation Produce eggs and sperm, pollen, spores

Meiosis is a form of cell division Growth

Larger organisms (toddler to teen) Renewal

Replace shed skin cells Repair

Fix a wound

Genetically Identical Daughter Cells

Copying of genetic material Accuracy generation after generation

Equal distribution of genetic material copies Precision – with no dilution

Even distribution of cytoplasm and membrane

Physical separation of the two new cells Each cell is half of the parent, parent

doesn’t exist as an individual anymore, yet isn’t gone……

Chromosome Redistribution

Genome entire genetic information for an individual or species

Chromosomes manageable packages of DNA

Somatic cells body cells, contain a set number of chromosomes for their species; humans 23 pairs (46)

Gametes reproductive cells like egg and sperm that have only 1 of each chromosome; humans one set of 23

Chromatincomplex of protein and DNA that is very long and linear

More terminology

Sister chromatids duplicated chromosomes, identical information, initially attached to each other

Centromere waist region of chromatid (arm and cohesions)

Mitosis division of a eukaryotic nucleus

Cytokinesis division of the cytoplasm

Meiosis process that generates gametes

The Cell Cycle

Interphase G1 – normal growth (originally “gap”) S – synthesis of DNA; replication of chromosomes G2 – extra proteins and cytoplasmic organelles

like mitochondria Mitotic Phase - “mitosis”

Prophase Prometaphase Metaphase division of the nucleus Anaphase Telophase

Cytokinesis - physical division of the cytoplasm

Phases of mitosis

Details of Phases

Interphase G1- gap one, not much visible, cell is

growing, normal- everyday life, accessing DNA, making proteins

S – synthesis of new DNA, all or nothing event, replication of chromosomes in entirety

G2 – now ready to divide nucleus, produce new structures for after division like ER and mitochondria

Details of phases

Mitosis Prophase – chromatin is chromosomes, visible

structure, packaged format Prometaphase – centrosomes move apart,

spindle forms, spindles attach to kinetochores, tug-o-war

Metaphase- phase where chromosmes are aligned at equator

Anaphase – chromosomes are in motion, sister chromatids are separate

Telophase – 2 separate nuclei, return to chromatin

Details of phases

Cytokinesis Still part of mitosis (Interphase +

Mitosis = Cell Cycle) This is division of cytoplasm, as

opposed to division of the nucleus Overlaps with both interphase and

telophase (see pg 231)

Plant vs Animal

Binary fission

Mitosis, binary fission and in between

Binary fission = prokaryotes One chromosome No nuclear

membrane Less to organize

Mitosis = eukaryotes Multiple

chromosomes Nuclear membrane Organelles to

organize

Regulation of the cell cycle

Cytoplasmic (chemical) regulation Mechanical (physical) regulation

Separate PPT

Lack of regulation in the cell cycle Cells which don’t respond to check point

signals within the cell or to physical conditions like contact tend to divide out of control and are called cancer cells. Own blood supply Use lots of nutrients Transformation turns normal cell into cancer

cell (related to microtubles, genetic? environmental? )

Mass of extra cells is tumor (benign) Malignant tumors invade other tissues and

organs Spreading of cancer cells is called metastasis