Meiosis Concept Presentation
Riffat Asif and Ezgi Cetinkaya
D 2.2. and D 3.1
Meiosis Square Dance
• http://www.youtube.com/watch?v=iCL6d0Ow
Kt8
Curriculum Expectations
• D 2.2 : investigate the process of meiosis,
using a microscope or similar instrument, or a
computer simulation, and draw biological
diagrams to help explain the main phases in
the process
• D 3.1 : explain the phases in the process of
meiosis in terms of cell division, the
movement of chromosomes, and crossing
over of genetic material
Lesson Sequence
Meiosis I
Prophase I
Metaphase I
Anaphase I
Telophase I
Interkinesis
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Cytokinesis
Who Cares?
 No Meiosis, No Fertilization.
No Fertilization, No Offspring.
No Offspring, No Family, No Future
Student Misconceptions/Difficulties
• Students may have trouble differentiating
between the stages of meiosis and mitosis.
Have them compare these two processes in a
chart or via a graphic organizer
Meiosis
And
Mitosis
What D o We Know about Mitosis?
Makes Two Identical Daughter Cells
Sister Cell Are Diploid
Growth and Repair Of Tissue
MITOSIS
Essential For Growth And Repair of Animals, Plants
Human Tissue.
Mitosis will
heal my
Wounds
Sooner Mitosis
Happens the
sooner I can get
this thing out of my
head
Meiosis vs. Mitosis (A comparison)
MITOSIS
MEIOSIS
Occurs in somatic cells
Occurs in germ cells as part of the
sexual cycle
Haploid and diploid cells can
undergo mitosis- one round of
division
Only diploid cells undergo meiosis- 2
rounds of division, meiosis I and II
Preceded by S phase- chromosome
duplication
Chromosomes duplicate before
meiosis I but not before meiosis II
Homologous chromosomes do not
pair
Homologous chromosomes pair
along their length during prophase of
meiosis I
Genetic exchange between
homologous chromosomes very rare
Crossing-over occurs between
homologous chromosomes during
prophase of meiosis I
Mitosis vs. Meiosis continued
MITOSIS
MEIOSIS
Sister chromatids attach to spindle
fibers from opposite poles during
metaphase
Sister chromatids do not attach,
rather homologous chromosomes
attach to spindle fibers from
opposite poles during metaphase I
Centromere splits at the beginning
of anaphase
Centromere does NOT split during
meiosis I
-
Sister chromatids attach to spindle
fibers from opposite poles during
metaphase II
-
Centromere splits at the beginning
of anaphase II
Produces 2 new daughter cells,
identical to each other and the
original cell
Produces 4 haploid cells, one (egg)
or all (sperm) of which can become
gametes- none is identical to each
other or to original cell
Meiosis I
Meiosis I
Prophase I
Metaphase I
Anaphase I
Telophase I
Interkinesis
Prophase I
• Chromosomes thicken becoming visible
• Centrosomes begin to move
toward opposite poles
• Crossing over, genetic
exchange between non-sister
chromatids
• Spindle begins to form
Metaphase I
• Tetrads line up along metaphase plate
• Each chromosome of a
homologous pair attaches fibers
from opposite poles
• Sister chromatids attach to
fibers from the same pole
Anaphase I
• Centromere does not divide
• Chiasmata migrate off
chromatid ends
• Homologous chromosomes
move to opposite poles
Telophase I
• Nuclear envelope re-forms
• Result: cells have half the # of
chromosomes, each consisting
of two sister chromatids
Interkinesis
• No chromosomal duplication (as opposed to
mitosis)
• In some species chromosomes decondense
Meiosis II
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Cytokinesis
Prophase II
• Chromosomes condense
• Centrioles move towards opposite
poles
• *Nuclear envelope breaks down at
the end of prophase II
Metaphase II
• Chromosomes align at the metaphase
plate
• Sister chromatids attach to spindle
fibers from opposite poles
Anaphase II
• Centromeres divide
• Sister chromatids
move to opposite poles
Telophase II
• Chromosomes begin to uncoil
• Nuclear envelopes and
Nucleoli reform
Cytokinesis
• Cytoplasm divides
forming 4 new haploid
cells
Great Educational Video Clips
• http://www.cellsalive.com/meiosis.htm
• Allows students to become active in their learning
• http://www.youtube.com/watch?v=R_LUJSqeSrI
• An excellent video that is great to apply especially
for those kinesthetic learners
Meiosis Virtual Lab
• A great virtual lab that students can
investigate online
http://bio.rutgers.edu/~gb101/lab10_meiosis/m
eiosis_web/index10.html
Virtual Lab
• Students are able to become active in their
learning, they are able to identify each of the
stages through various microscopic images.
Information is provided for them throughout
the activity
• There is also a section in the lab where
students are able to construct karyotypes- can
be provided for those students who need to
be further challenged
Some Virtual Lab Activities
Click the image above to choose the stage of
meiosis I the cells are in
Click on one of the cells above to get meiosis
stage II choices
Safety Considerations for Lab
• Students should be monitored during the
virtual lab activity to make sure that they are
not using the wrong website and to make sure
that they are staying on track to the activity
• Internet safety- usually schools sets up
firewalls to avoid unsafe websites but make
sure to educate both yourself and students of
the risks involved with internet safety
Exploring Further: Practical and
Societal Applications
Significance of Meiosis:
 Genetic Variation caused by the possible
combinations of chromosomes during
“Crossing Over” in Meiosis 1.
 Crossing over increase genetic diversity
as the genes on the chromosomes
combine in number of ways.
 An alteration in the DNA structure during
meiosis cause mutations.
 In most cases mutations are maladaptive
and the new cell dies.
 A small number of mutations are viable ----- the cell survives.
If the mutant gamete combines with another gamete to produce
an offspring ---- the mutation can be passed to the next generation.
Exploring Further: Practical and
Societal Applications
GENETIC DISORDERS AND
MUTATIONS:
 Sometimes the chromosomes
after crossing over separates
and move to one pole instead
of opposite poles.
 When the chromosomes do not
separate it is called as:
“ non disjunction”.
 The gametes with extra
chromosome fertilize, the
zygote has three chromosomes
instead of the normal 2.
This is called “Trisomy of
chromosome 21”
Exploring Further: Practical and
Societal Applications
Traits and Phenotype of animals
 Traits are distinguished characteristics
that are inherited.
 Traits are inherited in discrete units
called genes located on the
chromosomes.
Exploring Further: Practical and
Societal Applications
Trisomy 21 ----- Down Syndrome
 The most common chromosomal disorder with incidence
of 1:700 live births in U.S.
 High correlation between maternal age and meiotic nondisjunction” leading to Trisomy 21.
 Other abnormalities related to Trisomy 21 are:

Congenial heart disease

Dimorphic features

Mental retardation

Predisposition to Leukemia

Abnormal Immune response

Auto immunity
Differentiated Assessment
• Guided practice and formative assessment,
summative assessment
• Brain-storming activities, presentation of videos
for refreshing students’ prior knowledge
• Graphic organizers
• Different activities and presentation styles to gear
to the many learning styles, ELL and IEL learners
(e.g. youtube video presents an excellent activity
for the kinesthetic learners)
More Resources and References
• http://www.carolguze.com/text/442-3cell_cycle_mitosis_meiosis.shtml
• http://www.biology.iupui.edu/biocourses/N100/
2k4ch9meiosisnotes.html
• http://www.uic.edu/classes/bios/bios100/lecture
sf04am/lect16.htm
• Hartwell, L., Hood, L., Goldberg, M., Reynolds, A.,
Silver, L., & Veres, R. (2008). Genetics: From genes
to genomes. (3rd ed., pp. 96-97). New York:
McGraw-Hill