MEIOSIS
Q2 WK3 D2
Meiosis
Meiosis is the type of cell division by which
germ cells (eggs and sperm) are produced.
One parent cell produces four daughter
cells.
Daughter cells have half the number of
chromosomes found in the parent cell
Meiosis
During meiosis, DNA replicates
once, but the nucleus divides twice.
There are 2 parts to Meiosis:
1. Meiosis 1
2. Meiosis 2
The 4 new daughter cells have variation
of the parent DNA; this is genetic
variation
Meiosis Terminology
• Karyotype: Arranging of chromosomes from
largest to smallest; pairing up the homologous
chromosomes
• Autosomes: All non-sex chromosomes; (#1-22
for humans)
• Sex Chromosomes: Chromosomes that
determine the sex of an organism (#23 for
humans)
• Set (n): # of different chromosomes.
REMEMBER: Haploid = 1set, Diploid= 2 sets
Amniocentesis
Karyotype of a human
• Is this person male or
female?
• How many sex
chromosomes are
present?
• How many autosome
chromosomes are
present?
• How many homologous
pairs of chromosomes are
present?
Background on Meiosis
• Meiosis involves 2 divisions of the nucleus
– Meiosis 1 & Meiosis 2
Meiosis STARTS with HOMOLOGOUS
CHROMOSOMES
Homologous Chromosomes: They are
similar in shape, size & genetic content
Meiosis 1: 1st Division of Meiosis
• Prophase I: Chromosomes
condense, nuclear envelope
breaks, homologous
chromosomes pair at ends.
• ***Cross-Over:
Part of
chromatid on 1 homologous
chromosome exchanges with
the other chromosome***
Meiosis 1: 1st Division of Meiosis
• Metaphase I: Homologous chromosomes
move to center of the cell by the spindle
fibers.
• Anaphase I: Homologous chromosomes
separate and move to opposite poles, BUT
sister chromatids stay together. A set of
chromosomes moves to each pole
• Telophase I: The spindle fibers disappear,
cells begin to cleave; still, two sets of
chromosomes are at opposite poles
Meiosis 1
End of Meiosis I
• Once Meiosis I is
complete, cytokinesis
occurs and the cell
splits into 2 haploid
cells. These 2 cells
enter Meiosis II
Meiosis I: STOP & THINK
1. What is the purpose of Meiosis?
2. Describe genetic variation
3. Explain purpose of karyotyping
4. Explain cross-over
5. What major event occurs in Anaphase I ?
6. Are the daughter cells haploid or diploid? Explain
Meiosis I: Video
• http://www.youtube.com/watch?v=D1_mQS_FZ0
Meiosis II
• Prophase II: A new spindle forms around the
chromosomes (no longer HOMOLOGOUS
CHROMOSOMES)
• Metaphase II: Chromosomes line up at center &
spindle fibers attach to centromere
• Anaphase II: Centromeres split, chromatids
move to opposite poles of cell
• Telophase II: Nuclear envelope forms around
each set of chromosomes & spindles retracts, cell
begins cytokinesis
Result of Meiosis II
• 4 HAPLOID cells form as a result of Meiosis II
• Haploid = cell containing 1 set of
chromosomes
Meiosis II: 2nd division of Meiosis
Prophase II
http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html
Metaphase II
http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html
Telophase II
http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html
Meiosis I & II Venn Diagram
Meiosis I
Meiosis II
Meiosis Booklet 
1. Everyone needs 3 sheets of blank paper
2. Fold each one hotdog style
3. Cut straight up the fold
(You should have 6 long sheets, only use 5)
4. Label each square with the phases of meiosis
the same as the mitosis booklet
Meiosis Review Questions 
1. What type of cells are
used in Meiosis? Give
examples of these cells.
2. Meiosis is used in sexual
reproduction. Explain the
process of “cross-over”
3. Draw homologous
chromosomes going
through cross-over.
4.Meiosis is divided into
two parts, why?
5. Define “Haploid”
6. Compare and Contrast
Meiosis to Mitosis.
Mitosis & Meiosis
Comparison Worksheet 
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
http://www.usoe.k12.ut.us/curr/science/sciber00/7th/gen
etics/sciber/animatin.htm
Nov. 5th, 2013
Q2 WK4 D2
Meiosis & Genetic Variation