Chapter 11- The Cell Cycle
-Mitosis and cytokinesis is responsible for growth, wound repair and reproduction
-Mitotic (M) Phase: Dividing phase of cells
-Interphase: non-dividing phase. G ph1se, S (synthesis) phase- DNAsynthesis, G phase 2
-Key events of cell cycle are:
1. Replication of hereditary material in chromosomes
2. Partitioning of copied chromosomes to the two daughter cells during M phase.
- Gap phases important because cells replicate organelles, manufacture additional cytoplasm, grow large
enogh and synthesize enough organelles that its daughter cells will be normal in size and function.
11.2 How Does Mitosis Take Place?
-Mitosis results in the division of replicated chromosomes and the formation of two daughter nuclei with
identical chromosomes and genes.
-Humans and potatoes have 46 chromosomes.
-Eukaryotic chromosomes normally exist as long threadlike strands consisting of DNAassociated with
globular proteins called histones. In eukaryotes the DNA-protein material is called chromatin.
-Chromatid: each of the DNAcopies in the replicated chromosomes. Chromatids from same
chromosome are sister chromatids.
-Joined together along entire length as well as specialized region called centromere.
-Sister chromatids represent exact copies of the same genetic info. Each contains one long DNAdouble
helix.At start of M phase, then, each chromosome consists of 2 sister chromatids that are attached to each
other at centromere.
-During mitosis, sister chromatids separate to form independent chromosomes, one copy goes to each of
the two daughter cells.
-Sub-phases of mitosis: prophase, prometaphase, metaphase, anaphase, telophase (IPPMAT)
Before Mitosis: Interphase
After chromosome replication, each chromosome is
composed of two sister chromatids. Centrosomes have
replicated. MITOSIS: Sister chromatids separate; one chromosome copy goes to each daughter nucleus
3. Prometaphase: Chromosomes 6. Telophase: The
complete migration to
2. Prophase: Nucleolus middle of cell 5. Anaphase: Sister nuclear envelope
Chromosomes disappears.Nuclear chromatids separate. re-forms, and the
envelope breaks metaphase plate. spindle apparatus
condense and Being pulled in Chromosomes are
mitotic spindle down. Spindle fibres opposite directions by pulled to opposite disintegrates.
begins to form contract poles of cell.
chromosomes at kinetochore spindle
7. Cell division begins:Actin-myosin ring causes the
plasma membrane to begin pinching in. CleavageCYTOKINESIS
furrow 8. Cell division is complete: Two daughter cells form Mitotic spindle: Structure that produces mechanical forces that pull chromosomes into daughter cells
Spindle fibers: groups of microtubules attach to the chromosomes
Centrosome: microtubule organizing centre. Contains a pair of centrioles.
Kinetochore: located at centromere region of chromosome. Spindle fibers attach.
Centriole: Cylindrical structures that comprise microtubules, located inside animal centrosomes.
-Kinetochore microtubules remain stationary during anaphase. Instead of sliding past each other as actin
fibers do, microtubules shorten at the kinetochore because tubulin subunits are lost from the plus ends. As
kinetochore microtubules shorten at the kinetochore, the chromosomes are pulled along.
-As anaphase gets under way, proteins in the kinetochore catalyze the loss of tu