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Chromosomes and Mitosis
Eukaryotic Chromosomes
Made of DNA and protein
When a cell is not dividing,
chromosomes are long, thin strands of
chromatin
Function is to pass on traits
Structure of chromosome:
– Sister chromatids – copied DNA
– Centromere – attaches each pair of
chromatids
Each organism has a characteristic # of
chromosomes
– Ex. Humans have 46 chromosomes
Sexually reproducing organisms have 2
sets of homologous chromosomes w/
same genetic info
Mitosis
Division of nucleus
Occurs in 4 stages: PMAT
– Prophase
– Metaphase
– Anaphase
– Telophase
http://www.stolaf.edu/people/giannini/flash
animat/celldivision/crome3.swf
Phase 1: Prophase
– Chromosomes become visible
– Centrioles move to either side
of cell
– Spindle fibers form
– Chromosomes attach to
spindle at centromeres
– Nuclear membrane and
nucleolus disappear
– KEY WORD: PAIR
Phase 2: Metaphase
– Chromosomes line up along
the middle of the cell
– KEY WORD: MIDDLE
Phase 3: Anaphase
– Sister chromatids separate
into individual chromosomes
– Chromosomes move to either
end of the cell
– KEY WORDS: APART &
AWAY
Phase 4: Telophase
– Chromosomes uncoil
– Nuclear membrane forms
around each set of
chromosomes
– Nucleolus reappears
– KEY WORD: TWO NUCLEI
Mitosis is followed by
cytokinesis
– Cleavage furrow in animal
cells
– Cell plate in plant cells
Summary:
Results in 2 daughter cells which are
identical to the parent cell
Form of asexual reproduction
Used for growth and repair of tissue
Unicellular organisms use it to reproduce