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MEIOSIS
VOCABULARY
Chromatin
All of the
DNA in an
uncondensed
(spaghettilike) form
Chromosomes
A
double rod
of condensed
chromatin
 Sister
Chromatids: the two halves of
a chromosome; half original, half
rebuilt
 Homologous
Chromosomes (pairs):
chromosomes containing the same
gene (possibly different alleles)
one from mom, one from dad
 Line up together in tetrads during
meiosis

Centromeres:
the region of
DNA where 2 sister
chromatids come together
Spindle
Fibers: fibers that
attach to sister chromatids
and bring them to opposite
poles during meiosis
TYPES OF CELLS
Diploid
 Cells
that contain
double the amount
of chromosomes
than haploid cells
 Usually called the
“normal” number
of chromosomes
 Two copies of each
gene
Haploid
 Cells
that contain
half the amount of
chromosomes than
diploid cells
 One copy of each
gene
TETRADS
How
the chromosomes line up
during Metaphase I of meiosis
Homologous chromosomes and
their copies (sister chromatids)
line up
SEGREGATION
 Homologous
chromosomes randomly
line up in tetrad formation during
meiosis
 Many possibilities for the
combination of alleles in offspring
Two
possibilities
of lining up
CROSSING-OVER
 Exchange
of genes between
homologous chromosomes during
meiosis
 Adds
more variation