1. Meiosis Concept Presentation Riffat Asif and Ezgi Cetinkaya
D 2.2. and D 3.1

2. Meiosis Square Dance

3. 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

4. Lesson Sequence
Meiosis I Prophase I Metaphase I Anaphase I Telophase I Interkinesis
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Cytokinesis

5. Who Cares? No Meiosis, No Fertilization.
No Fertilization, No Offspring.
No Offspring, No Family, No Future

6. 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

7. Meiosis
And Mitosis

8. What D o We Know about Mitosis?
Makes Two Identical Daughter Cells
Sister Cell Are Diploid
Growth and Repair Of Tissue

9. Mitosis will help me grow
Essential For Growth And Repair of Animals, Plants
Human Tissue.
Mitosis will help me grow

10. Sooner Mitosis Happens the sooner I can get this thing out of my head
Mitosis will heal my Wounds

12. Meiosis vs. Mitosis (A comparison)
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

13. Mitosis vs. Meiosis continued
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

14. Meiosis I
Meiosis I Prophase I Metaphase I Anaphase I Telophase I Interkinesis

15. 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

16. 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

17. Anaphase I Centromere does not divide Chiasmata migrate off
chromatid ends
Homologous chromosomes
move to opposite poles

18. Telophase I Nuclear envelope re-forms Result: cells have half the # of
chromosomes, each consisting
of two sister chromatids

19. Interkinesis No chromosomal duplication (as opposed to mitosis)
In some species chromosomes decondense

20. Meiosis II Meiosis II Prophase II Metaphase II Anaphase II
Telophase II
Cytokinesis

21. Prophase II Chromosomes condense Centrioles move towards opposite
poles
*Nuclear envelope breaks down at
the end of prophase II

22. Metaphase II Chromosomes align at the metaphase plate
Sister chromatids attach to spindle
fibers from opposite poles

23. Anaphase II Centromeres divide Sister chromatids
move to opposite poles

24. Telophase II Chromosomes begin to uncoil Nuclear envelopes and
Nucleoli reform

25. Cytokinesis
Cytoplasm divides
forming 4 new haploid
cells

26. Great Educational Video Clips
Allows students to become active in their learning
An excellent video that is great to apply especially
for those kinesthetic learners

27. Meiosis Virtual Lab
A great virtual lab that students can investigate online

28. 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

29. 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

30. 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

31. 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.

32. 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”

33. 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.

34. Exploring Further: Practical and Societal Applications
Trisomy Down Syndrome
The most common chromosomal disorder with incidence
of 1:700 live births in U.S.
High correlation between maternal age and meiotic non-
disjunction” 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

35. 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)

36. More Resources and References
Hartwell, L., Hood, L., Goldberg, M., Reynolds, A., Silver, L., & Veres, R. (2008). Genetics: From genes to genomes. (3rd ed., pp ). New York: McGraw-Hill