Cell and Molecular Biology
Mitosis and Meiosis
Behrouz Mahmoudi
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MITOSIS – “Double and
Divide”
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MITOSIS: all duplicated chromosomes separate
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Chromosomes in the prometaphase stage
of mitosis, from a cell in the flower of
Haemanthus.
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MITOSIS steps 0-1 – Interphase and Prophase
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MITOSIS steps 2-4– Metaphase, Anaphase, Telophase
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Centromere locations and designations of chromosomes based on
centromere location. Note that the shape of the chromosome during
anaphase is determined by the position of the centromere.
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The phases of the cell cycle. Following mitosis (M), cells enter the G1 stage of interphase, initiating a
new cycle. Cells may become nondividing (G0) or continue through G1, where they become committed
to begin DNA synthesis (S) and complete the cycle (G2 and M). Following mitosis, two daughter cells 19
are produced and the cycle begins anew for each cell.
The length of time spent in each phase of one complete
cell cycle of a human cell in culture. Actual times vary
according to cell types and conditions.
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Mitosis in an animal cell with a
diploid number of 2n = 4. The
events occurring in each stage are
described in the text. Of the two
homologous pairs of
chromosomes, one contains longer,
metacentric arms and the other,
shorter, submetacentric arms. The
maternal chromosome and paternal
chromosome of each pair are
shown in different colors. Part (g)
illustrates the formation of the cell
plate and lack of centrioles in a
plant cell.
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the formation of the
cell plate and lack of
centrioles in a plant
cell.
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The three major checkpoints within the cell
cycle that regulate its progress.
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MEIOSIS
• MAKING REPRODUCTIVE CELLS (SPERM AND
EGG) inr eproductive organs (testis, ovary)
• SIMILAR TO MEIOSIS BUT TWO STEPS, the
idea is to reduce a double set to single –
so single sets from two parents can join in
fertilization to produce baby’s double set
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Homologous (matching) chromosomes
come from your two parents – you have
TWO SETS of chromosomes!
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Overview of the major events and
outcomes of mitosis and meiosis.
Two pairs of homologous
chromosomes are followed.
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The substages of meiotic prophase I
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The major events during
meiosis in an animal with a
diploid number of 2n = 4
beginning with metaphase I.
Note that the combination of
chromosomes in the cells
produced following telophase
II depends on the random
alignment of each tetrad and
dyad on the metaphase plate
during metaphase I and
metaphase II. Several other
combinations (not shown)
can also be formed.
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Spermatogenesis
and oogenesis in
animal cells.
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Mitosis and Meiosis Compared
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Alternation of
generations between the
diploid sporophyte (2n)
and the haploid
gametophyte (n) in a
multicellular plant. This is
an angiosperm, where
the sporophyte stage is
the predominant phase.
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A diagram of the mitotic chromosome and its various
components, showing how chromatin is condensed into
it.
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