Meiosis Flip Book Checklist
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Meiosis is a special type of cell division necessary for sexual reproduction in eukaryotes, such as animals,
plants and fungi. The number of sets of chromosomes in the cell undergoing meiosis is reduced to half the
original number, typically from two sets (diploid) to one set (haploid). The cells produced by meiosis are either
gametes (the usual case in animals) or otherwise usually spores from which gametes are ultimately produced
(the case in land plants). In many organisms, including all animals and land plants (but not some other groups
such as fungi), gametes are called sperm in males and egg cells or ova in females. Since meiosis has halved the
number of sets of chromosomes, when two gametes fuse during fertilization, the number of sets of
chromosomes in the resulting zygote, is restored to the original number.
Meiotic division occurs in two stages, meiosis I and meiosis II, dividing the cells once at each stage. The first
stage begins with a diploid cell that has two copies of each type of chromosome, one from each the mother
and father, called homologous chromosomes. All homologous chromosomes pair up and may exchange
genetic material with each other in a process called crossing over. Each pair then separates as two haploid
cells are formed, each with one chromosome from every homologous pair.
In the second stage, each chromosome splits into two, with each half, called a sister chromatid, being
separated into two new cells, which are still haploid. This occurs in both of the haploid cells formed in meiosis
I. Therefore from each original cell, four genetically distinct haploid cells are produced. These cells can mature
into gametes.
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Before Meiosis begins, the Diploid
cell undergoes Interphase. This
creates additional copies of DNA and
homologous chromosomes are
present.
Prophase I
o Homologous Chromosomes
join and form a tetrad.
o While the chromosomes are
attached to each other, parts
of the chromosomes change
location with each other. This
process is called Crossing-Over
and it is responsible for
producing genetic diversity.
o Nucleus and Nucleolus
disappear.
o Centrioles produce spindle
fibers and move away from
each other.
Metaphase I
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Homologous Chromosome Pairs align
in the center of the cell.
Centrioles are at opposite sides of the
cells and spindle fibers are attached
to the paired chromosomes.
Anaphase I
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Homologous Chromosome Pairs
separate and move to opposite ends
of the cell.
Telophase I
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Nucleus and Nucleolus reappear and
the homologous chromosomes
uncoil.
Cytokinesis
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Depending on the organism, the cell
undergoes cytokinesis to become 2
cells with homologous chromosomes
in each.
Prophase II
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Nucleus and Nucleolus disappear.
Homologous Chromosomes condense
Centrioles produce spindle fibers and
move away from each other.
Metaphase II
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Homologous chromosomes align in
the center of the cell
Centrioles are at opposite ends
Anaphase II
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Homologous chromosomes are
separated into sister chromatids and
these move away from each other.
Telophase II
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Sister Chromatids at opposite ends of
the cell uncoil.
Nucleus and Nucleolus reappear
around the chromatids.
Cytokinesis takes place and there are 4
haploid, genetically different daughter cells.
Females produce an egg by oogenesis. This
occurs in the ovaries (female reproductive
organs).
Males produce sperm by spermatogenesis.
This occurs in the testes (male reproductive
organs).