2. Chromosomes become visible
during cell division
A karyotype displays the
chromosomes
• Karyotype
– Display of the
chromosomes
– 23 pairs of chromosomes
– 46 total chromosomes
– One member of each pair
comes from the father, the
other member comes from
the mother
3. • Autosomes
– Have nothing to do with gender
– 22 pairs
• Sex chromosomes
– Determines gender
– XY is male
– XX is female
• Homologous pair
– Pair of autosomal chromosomes
– Look alike
– Carry genes for the same trait (earlobe, hairline,
finger length)
4. • Sister chromatids
– Duplicated chromosome required for mitosis
• Centromere
– Holds together sister chromatids
• Kinetochores
– Protein complexes at centromere where spindle fiber
attaches during cell division
5. The eukaryotic cell cycle has a set series of stages
• Cell cycle
– Series of stages of cell growth and
division
• Interphase
– Time between cell division
• G1 Stage
– Recovery from division
– Decides whether to divide or not
» Enters G0 if it is not going to
divide where it will continue
normal processes
– If it is going to divide, it doubles in
size, double organelles, accumulates
molecules needed for DNA synthesis
• S Stage
– DNA replicated resulting in sister
chromatids
• G2 Stage
– Organelle replication continues
– Makes proteins (microtubules)
needed for cell division
6. M stage (mitosis)
• Cell division
• Chromosomes
divided between 2
cells
• Cytokinesis
– Division of cytoplasm
7. Mitosis maintains the chromosome
number
Following mitosis, daughter cells
have the same chromosome
count as the parent cell
• Parent cell
– Original cell
• Daughter cells
– 2 new cells
• When cells enter M stage, it has
sister chromatids (duplicated
chromosomes)
• Animal cell are diploid (2n)
throughout mitosis (chromosomes
are in pairs)
• Some protists and fungi are
haploid (n) before and after
mitosis
8. The spindle apparatus
• Centrosome
– Divides at the start of
nuclear division
– Produce spindle fibers,
which assist
separation of the
chromatids as they
move to opposite
poles
9. Mitosis has a set series of phases
Early prophase
• Centrosomes divided
• Chromatin condensing into chomosomes
• Nuclear envelope fragmenting
Prophase
• Nucleolus disappeared
• Duplicated chromosomes (sister chromatids)
visible
• Centosomes begin moving apart
• Spindle is in the process of forming
10.
11. Early metaphase
• Each duplicated chromosomes attached
to the spindle apparatus
• Spindle fibers stretch from each pole
Metaphase
• Centromeres of duplicated chromosomes
are aligned at equator
• Kinetochores attach sister chromatids to
spindle fibers that come from opposite
poles
12.
13. Anaphase
• Sister chromatids part and become
daughter chromosomes that are pulled
toward the poles
Telophase
• Daughter cells are forming
• Nuclear envelopes and nucleoli reappear
• Chromosomes become chromatin
14.
15. Contribution of the Cell Cycle to
Human Health
Cell division allows a fertilized egg to
develop into a newborn and is also
important in repairing damage to your
body like broken bones and cuts.
16. Cytokinesis divides the cytoplasm
Animal cell cytokinesis
• Cleavage furrow
forms between the
two daughter cells
• Furrow deepens
when the contractile
ring forms between
cells and continues to
tighten
• 2 independent
daughter cells result
17. Plant cell cytokinesis
• A new plasma membrane (cell plate)
comes between the new cells
• The new membrane releases molecules
that form a new cell wall between the new
cells
