mitosis & cytokinesis filea genome –is the complete set of an organism’s genes –is located...
TRANSCRIPT
A genome
– Is the complete set of an organism’s genes
– Is located mainly on DNA in the cell’s nucleus
• NAMES FOR DNA in different parts of the Cell Cycle
• Chromatin - DNA-protein complex
• Chromosome – condensed chromatin
• Chromatids –duplicated chromosomes
Eukaryotic Chromosomes
– Are made of
chromatin, a
combination of
DNA and protein
molecules
– Are not visible in
a cell until cell
division
• The DNA in a cell is
packed into an elaborate,
multilevel system of
coiling and folding
DNA double helix
Histones
“Beadson astring”
Nucleosome
Tight helical fiberSupercoil
Sisterchromatids
Centromere
Histones are a family of small,
positively charged proteins that coli
the DNA into the nucleus
Nucleosome = DNA + histones
In a repeating pattern
DNA DUPLICATION (INTERPHASE)
Before a cell divides DNA COPIES
DNA uncoils (G1 phase)
DNA duplicates (S phase)
DNA separates into smaller attached units called
sister chromatids (G2 phase)
Occurs in INTERPHASE
• When the cell divides,
the sister chromatids
separate from each
otherChromosomeduplication
Sisterchromatids
Chromosomedistribution
todaughter
cells
Attached by a centromere
• Mitosis
Mitosis and Cytokinesis
– Is the division
(separation)of the
chromosomes
Interphase
Centrosomes (with centriole pairs)
NucleolusNuclearenvelope
Plasmamembrane
Chromatin
• Mitosis consists of five distinct phases
–Prophase
–Metaphase
–Anaphase
–Telophase
–Cytokinesis
Earlymitoticspindle
Centrosome Centromere
Chromosome, consistingof two sister chromatids
Spindlemicrotubules
Fragments ofnuclear envelope
Metaphase
Spindle
ProphasePROPHASE
• Chromatin
condenses
• Nuclear
membrane
breaks down
• Nucleolus
disappears
• Chromatids
become
visible
• Microtubules,
spindle fibers
centrioles
form
METAPHASE
• Spindle
fibers attach
to the
centromere
• Chromatids
align in the
center
ANAPHASE
Sister chromatids
separate
Spindle fibers shorten
TELOPHASE
Identical chromosomes at the end
in each cell
Nuclear membrane starts forming
Chromosomes begin uncoiling
Anaphase Telophase and Cytokinesis
Daughterchromosomes
Cleavagefurrow
Nuclearenvelopeforming
Nucleolusforming
• CYTOKINESIS different in plant and
animal cells
ANIMAL: Cleavage Furrow
PLANT: cell plate divides then cell wall
forms
– Typically starts during telophase
– Is the division of the cytoplasm
Cleavagefurrow
Cleavage furrow Contracting ring ofmicrofilaments
Daughter cells
(a) Animal cell cytokinesis
Wall of parent cell
Cell plateforming
Daughternucleus
Cell wall
Vesicles containingcell wall material
Cell plate
New cell wall
Daughter cells(b) Plant cell cytokinesis