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Name:_______________________________ Date:_____________ Block:_________
Meiosis
Fill in the blank notes
GENES:
 Genes determine individual ______________________
 Genes do not exist ___________ in the ______________s of a cell; they are lined
up on _________________.
 A chromosome can contain a ______________ or more __________ along its
length.
 In the body, cells of most plants and animals chromosomes occur in
_____________.
 One chromosome in each pair come from the ___________ parent and the other
came from the ________________ parent.
 A cell with two of each kind of chromosome is called a _________________ cell.
 They are said to contain 2n number of ___________________.
 Each species of organisms contains a characteristic number of
_______________________.
 Humans have _____________ pairs of chromosomes or ____________ total.

WHY MEIOSIS?
 When cells divide by _________________, the new cells have exactly the
______________ number and kind of chromosomes as the original cell.
 The body uses meiosis to provide a cell for the purpose of
___________________.
 A cell produced by meiosis is said to be _______________ and contain n amount
of chromosomes
 This cell is called a _______________.
– An example of a gamete is ____________ (in males) and __________ (in
females)
– Produced by meiosis, gametes have ____________ the number of
chromosomes as a parent’s body cell.
 Meiosis consists of 2 separate _________________, known as meiosis ____ and
meiosis ________.
 Meiosis I begins with one _______________ (2n) cell. (just like mitosis).
 By the end of meiosis II there are ________ haploid (n) cells. (this is different
then mitosis).
 When a haploid (n) sperm cell _______________ a haploid egg (n) cell, the
resulting cell (called a zygote) once again has a _________________ (2n) number
of cells.
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The Phases of Meiosis
 ____________________
 ____________________
 ____________________
 ____________________
 ___________________
 ____________________
 ____________________
 ____________________
 ____________________
MEIOSIS I: INTERPHASE I
 Similar to ______________
 The cell _______________ its chromosomes. After replication each chromosome
consists of 2 identical ____________ chromatids, held together by a
_______________.
MEIOSIS I: PROPHASE
 Steps similar to prophase in mitosis:
– The DNA of the chromosomes __________ up.
– Centrioles migrate to opposite ______________ of the cell.
– The ______________ apparatus forms
– The nuclear envelope begins to ________________
 Steps different than prophase in mitosis:
– As the DNA coils, _______________________ chromosomes line up with
each other, gene by gene along their length, to form a four-part structure
called a __________________.
 Homologous chromosomes have genes for the ____________ trait,
such as height.
 A tetrad consist of two homologous chromosomes, each made up
of two sister chromatids. The chromatids in a tetrad pair so tightly
that ________________________
can occur.
 Crossing over is when non-sister chromatids from
homologous chromosomes ____________ and
_________________ genetic material.
 Crossing over:
– There are an average of _________ to
__________ crossovers for each pair of
homologous chromosomes
– Crossing over aids in genetic
_______________.
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MEIOSIS I: METAPHASE I
 The _____________________ of each chromosome become attached to a spindle
fiber
 The spindle fibers pull the ____________________ into the middle or equator, of
the spindle.
– this is different then in mitosis:
 In meiosis the homologous chromosomes are
lined up side by side as _______________.
In mitosis chromosomes line up on the
spindle’s equator ____________________
of each other.
MEIOSIS I: ANAPHASE I
 ____________________ chromosomes, each with its two chromatids, separate
and move to opposite ends of the cells.
– The _____________________ holding the sister chromatids together do
not split as they do during anaphase in mitosis.
MEOSIS I: TELOPHASE I
 ________________ is broken down
 Chromosomes _______________
 Cytoplasm ________________ to yield two new cells
 Each cell has _____________ the genetic information as the original cell because
it has only ____________ chromosome from each homologous pair.
 The daughter cells are genetically ___________________ from each other and the
parent.
 Another cell _________________________ is needed because each chromosome
is still _____________________.
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MEIOSIS II: PROPHASE II
 DNA _____________
 A __________________ forms
 _________________ migrate to opposite poles of the cell.
 _______________ envelope disintegrates
MEIOSIS II: METAPHASE II
The ______________________, made up of sister chromatids, are pulled to the center of
the cell and line up __________________ at the equator.
MEIOSIS II: ANAPHASE II
 The __________________ of each chromosome splits allowing the sister
chromatids to ____________________ and _________________ to opposite
poles.
MEIOSIS II: TELOPHASE
 Nuclei _____________
 The spindles ____________________
 The _________________ divides
RESULTS OF MEIOSIS:
 The events of meiosis II are _________________l to those of mitosis except that
the chromosomes do not _____________________ before they divide.
 At the end of meiosis II, ______________ haploid cells have been formed from
______________ diploid cell.
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