Meiosis - Chapter 7 Section 1 Notes
Mitosis vs. Meiosis
Mitosis:
 occurs because the cell gets _________________ and for
_________________.
 produces genetically identical _________________ daughter cells.
Meiosis:
 occurs in the production of _________________.
 produces _________________ daughter cells.
Somatic vs. Gametes
Somatic Cells –
 They are all the cells in the _________________ except for sperm and eggs
 Always _________________!
 Produced by _________________.
Gametes –
 In males – _________________/_________________ In females –
_________________
 Always _________________!
 Produced by _________________.
Gametes



Each sperm and egg cell contains _________________ the normal number of
chromosomes – essential to _________________ reproducing organisms.
When an egg is fertilized by the sperm, the offspring inherits _____________
for each homologous pair from each _________________.
It gains the _________________ number of chromosomes.
Overview of Meiosis
 Meiosis begins with a cell that has the normal number of
_________________.
 Due to the cell having completed the S (_________________) phase of the
cell cycle, the chromosome has replicated _________________.
 Meiosis produces _________________ through two stages of cell
_________________.
o Meiosis I: separation of _________________ chromosomes – with
each of the _____ new daughter cells get _____ chromosome from
each pair.
o Meiosis II: each chromosome is separated into ______ chromosomes,
so that each of the _____ daughter cells get ___________ the normal
number of chromosomes
Phases of meiosis
 During meiosis, two cell divisions – divided into 2 stages – stages _____ and
_____.

Each stage, the cell undergoes the same phases as mitosis: ______________,
______________, ______________ and _________________.
o Prophase I:
 _________________ _________________ breaks down.
 Homologous chromosomes _________________
 _________________ _________________ occurs.
Crossing-over
 Crossing-over occurs in _________________ after the homologous
chromosomes _________________.
 DNA strands from one chromosome join with the other, _________________
off and _________________ themselves back together.
 END RESULT: each chromosome contains pieces of DNA from its
_________________
 Result of Crossing-Over
o Each homolog has a slightly different set of _________________.
o Crossing-over _________________ the genetic material so that each
sister chromatid has a different combination of _________________.
o Instead of the _____ original allele combinations, there are now _____
o Crossing over makes it possible for offspring to inherit unique
_________________ of _________________ .
o This increases the _________________ _________________ in the
_________________ _________________ of a species.
Phases of Meiosis
 Metaphase I:
o Spindles attach to the centromeres of the _________________.
o Homologous chromosomes align at the _________________.
 Anaphase I:
o Spindles _________________
o Homologous chromosomes _________________
 Telophase I:
o _________________ occurs.
o _________________ cells have formed.
 Prophase II:
o Chromosomes _________________
o Spindle fibers _________________
 Metaphase II:
o Spindles attach to the _________________ of the sister chromatids.
o Chromosomes align at the _________________ .
 Anaphase II:
o Spindle fibers _________________ .
o Sister chromatids _________________ .
 Telophase II:
o Chromosomes begin to _________________ and stretch
_________________ .
o _________________ _________________ reforms.
o _________________ occurs.