Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis

1. The CellThe Cell
CycleCycle

2. In the time that itIn the time that it
takes you to readtakes you to read
this sentence, yourthis sentence, your
body will havebody will have
made millions ofmade millions of
new cells! Makingnew cells! Making
new cells allowsnew cells allows
you to grow andyou to grow and
replace cells thatreplace cells that
have died.have died.

3. The Life of a CellThe Life of a Cell
 Cell cycle: the life cycleCell cycle: the life cycle
of a cellof a cell
 Cell cycle begins when theCell cycle begins when the
cell iscell is formedformed and endsand ends
when the cell divides andwhen the cell divides and
forms new cellsforms new cells
 Before a cell divides, itBefore a cell divides, it
must make a copy of itsmust make a copy of its
DNADNA

4.  DNA is organized into structuresDNA is organized into structures
calledcalled CHROMOSOMESCHROMOSOMES
 Copying chromosomes ensures thatCopying chromosomes ensures that
each new cell will be an exacteach new cell will be an exact copycopy
of its parent cellof its parent cell

5. How does a cell make more cells?How does a cell make more cells?
Depends on whether it’sDepends on whether it’s
prokaryotic (no nucleus)prokaryotic (no nucleus)
oror
eukaryotic (with nucleus)eukaryotic (with nucleus)

6. Making More Prokaryotic CellsMaking More Prokaryotic Cells
 Prokaryotic cells areProkaryotic cells are lessless
complexcomplex than eukaryoticthan eukaryotic
cellscells
 Cell division is calledCell division is called
““binary fissionbinary fission”, which”, which
means “splitting into twomeans “splitting into two
parts”parts”
 Binary fission results in twoBinary fission results in two
cells that each contain onecells that each contain one
copycopy of the circle of DNAof the circle of DNA

7. Eukaryotic Cells and Their DNAEukaryotic Cells and Their DNA
 Eukaryotic cellsEukaryotic cells
are more complexare more complex
 The chromosomesThe chromosomes
of eukaryotic cellsof eukaryotic cells
contain morecontain more DNADNA
than prokaryoticthan prokaryotic
cellscells

8.  Different kinds ofDifferent kinds of
eukaryotes haveeukaryotes have
different numbersdifferent numbers
ofof chromosomeschromosomes
 Example: humansExample: humans
have 46have 46
chromosomeschromosomes

9. Think “more chromosomes = betterThink “more chromosomes = better
organism”?organism”?
Not true! Humans have 46, but a lot of organisms haveNot true! Humans have 46, but a lot of organisms have
more than us!more than us!
 Butterfly = 380Butterfly = 380
 Goldfish = 94Goldfish = 94
 Horse = 64Horse = 64
 Amoeba = 40Amoeba = 40
 Tobacco plant = 48Tobacco plant = 48

10.  Homologous chromosomes:Homologous chromosomes:
chromosomes that have thechromosomes that have the samesame
sequence of genes and the samesequence of genes and the same
structurestructure

11. Making More Eukaryotic CellsMaking More Eukaryotic Cells
 The eukaryotic cell cycle includesThe eukaryotic cell cycle includes 33 stages:stages:
1.1. InterphaseInterphase: cell grows and copies its: cell grows and copies its
organelles and chromosomesorganelles and chromosomes
2.2. Mitosis:Mitosis: complicated process ofcomplicated process of
chromosome separationchromosome separation
3.3. CytokinesisCytokinesis: cell splits into two cells; these: cell splits into two cells; these
cells are identical to each othercells are identical to each other

12. MitosisMitosis
•Cell division occurs in a series
of stages, or phases

13. 11stst
: INTERPHASE: INTERPHASE
 Not actually part ofNot actually part of
mitosismitosis
 Chromosomes areChromosomes are
copiedcopied (# doubles)(# doubles)
 -Each chromosome-Each chromosome
and its copy (sisterand its copy (sister
chromosome) changechromosome) change
to sister chromatids atto sister chromatids at
the end of this phasethe end of this phase
centromere

14. 22ndnd
: PROPHASE: PROPHASE
 MitosisMitosis begins (cellbegins (cell
begins to divide)begins to divide)
 Centrioles (or poles)Centrioles (or poles)
begin to move tobegin to move to
opposite sides of cellopposite sides of cell
 Spindle fibersSpindle fibers formform
between the polesbetween the poles

15. 33rdrd
: METAPHASE: METAPHASE
 Chromosomes lineChromosomes line
up downup down thethe
middlemiddle of the cellof the cell
 HomologousHomologous
chromosomes pairchromosomes pair
up and attach toup and attach to
the spindle fibersthe spindle fibers

16. 44thth
: ANAPHASE: ANAPHASE
 Chromatids (orChromatids (or
pairs ofpairs of
chromosomes)chromosomes)
separateseparate and moveand move
toto oppositeopposite ends ofends of
the cellthe cell

17. 55thth
:: TELOPHASETELOPHASE
 Two newTwo new nucleinuclei formform
 ChromosomesChromosomes
appear as chromatinappear as chromatin
((threadsthreads ratherrather
than rods)than rods)
 MitosisMitosis endsends

18. 66thth
: CYTOKINESIS: CYTOKINESIS
 Cell membrane movesCell membrane moves
inward to create twoinward to create two
daughterdaughter cells – eachcells – each
with its ownwith its own nucleusnucleus
with identicalwith identical
chromosomeschromosomes

19. Ways to Remember the Order ofWays to Remember the Order of
Mitosis!Mitosis!
II PProposedroposed MMarriagearriage AAfterfter TTuesday’suesday’s CClass.lass.
II PPickedicked MMelonselons AAtt TThehe CCircus.ircus.
Can you think ofCan you think of
any?any?