Mitosis and Meiosis
What is Mitosis?
• The process of cell division in all diploid
cells
• Constantly occurs in cells throughout plants
and animals at all times
–
–
–
–
Muscle cells
Skin cells
Stem cells
Cambium cells
• Results in two diploid daughter cells
Stages of Mitosis
•
•
•
•
•
•
Interphase
Prophase
Metaphase
Anaphase
Telephase
Cytokinesis
Interphase
• The period of cell
growth and function
prior to the beginning of
true mitosis, in which
the cells store energy
for cellular division
– The cell replicates DNA
and produces chromatid
pairs
– This is the longest period
in the life of a cell
Prophase
• The first true stage of mitosis
• The nuclear membrane dissolves,
centromeres form, and centrioles move
toward opposite ends of the cell
Metaphase
• The second and
shortest stage of mitosis
• Chromatids align in the
center of the cell and
spindle fibers attach to
centromeres from
centrioles
Anaphase
• The third stage of mitosis
• Chromatids are separated
and pulled towards
opposite ends of the cell
by spindle fibers
• Errors in the transmission
of genetic information are
most likely to occur at this
stage
Telephase
• The final and longest
stage of mitosis
• Chromosomes reach
opposite ends of the
cell, and new nuclear
membranes form for
each new daughter cell
Cytokinesis
• The actual division of daughter cells at the
end of mitosis
• A cleavage furrow forms pinching apart
cells in animals
• In plant cells, a cell plate forms between
daughter cells, dividing cells and forming
the new section of the cell wall.
Cytokinesis
What is Meiosis?
• The specialized form of cell division that
occurs only in haploid cells
–
–
–
–
Sperm
Egg
Pollen
Ovum
• Very similar in process to mitosis, except
with two cycles, producing 4 haploid
daughter cells (23 chromosomes each)
Spermatogenesis
• Production of male sex cells through
meiosis
• Produces 4 sperm
Oogenesis
• Production of female sex cells through
meiosis
• Usually produces 1 viable egg-other 3 abort
Stages of Meiosis
•
•
•
•
Interphase
Meiosis I
Meiosis II
The stages of Meiosis I and Meiosis II are
identical to the stages of Mitosis, but with
different cells for a different purpose
Interphase
• Same as mitosis
• Period of growth and function
Meiosis I
•
•
•
•
•
Prophase I
Metaphase I
Anaphase I
Telephase I
Cytokinesis
– Reduction process-changes cells from diploid to
haploid
Meiosis II
• Prophase II
– Prophase II is responsible for aligning
chromosomes for the final division
•
•
•
•
Metaphase II
Anaphase II
Telephase II
Cytokinesis