Download Meiosis II: (Division of chromatids)

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EX 14 Meiosis & Gel electrophoresis
Reduction Division and Gametogenesis
Objectives: In this exercise, we will look at cells in meiosis under microscopes and
understand movement of chromosomes. The goal is to identify each phase of meiosis
and distinguish cell divisions between mitosis and meiosis. Further, we will survey on
gametogenesis of mammals. Certainly, I expect you to be able to explain meiosis and
mitosis without confusion to your friends by the final exam.
Be familiar with terms and instruments used in the electrophoresis. Understand
the mechanism of the experiments so that you will be able to perform this experiment
later in this semester.
Gel Electrophoresis: (Introduction) Æ Ex 7
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Another method to isolate molecules have electric-charges, DNA, RNA, and
proteins (amino acids) with electric current as separating force and a gel as the
matrix. Molecules are separated due to their sizes and electric charges.
Pay attention to the direction at which molecules move in the gel.
Read the handout.
We will come back to this experiment once more before the final.
Micropipetters: Measures volume in micro-litter (µL). You need to know
how to adjust the volumes in each micropipetter; there are different sizes.
Meiosis:
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Purpose of meiosis is to produce gametes (eggs and sperms) that have half the
number of chromosomes as the original cells (=haploid).
Why haploid?
Æ So that when fertilized, the original number of chromosomes is
restored.
Æ Genetic variation.
Where does meiosis occur?
Æ Animal:
Æ Plants:
Key Words: (Define & Understand events):
• Diploid / Haploid:
• Homologous chromosome:
• Synapsis:
• Tetrad:
• Allele:
• Crossing over:
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(With figure 14.2)
Meiosis I: (Reduction division/ Division of homologous chromosomes)
¾ Prophase I:
¾ Metaphase I:
¾ Anaphase I:
¾ Telophase I:
¾ Daughter cells:
• Which chromosomes will be apart? (Homologous or Chromatids)
• Are cells diploid or haploid at the end of meiosis I?
• There may be a slight delay (pause) in between meiosis I and II.
Meiosis II: (Division of chromatids)
¾ Prophase II:
¾ Metaphase II:
¾ Anaphase II:
¾ Telophase II:
¾ Daughter cells
• Which chromosomes will be apart? (Homologous or Chromatids)
• Are cells diploid or haploid at the end of meiosis II?
• When and how does cross over occur?
• When does crossing over may occur?
• What is tetrad?
Gametogenesis:
Key Words: (Define & Understand events):
(Mammals)
™ Gamete:
™ Spermatogenesis:
™ Oogenesis:
• 2 ~3 million primary oocytes produced during fetal development.
(About 700,000 are present at birth; by puberty, number reduced to
~300,000.)
• I expect you to know names of cells at each stages of both gametogenesis. i.e.
Brief reproduction of the figure 14.3, 14.4, & 14.5.
• Read though this section pp147-149.
• Which cells are diploid and which are haploid in gametogenesis?
™ Fertilization:
™ (Plants)
™ Locations of meiosis:
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For Today:
1. Gel Electrophoresis (Demo)
2. Video (Part III)
3. Work on all questions and filling in tables on Ex14.
4. Procedure 14.1 with magnets and beads.
5. Procedure 14.2 (slides)
1. Testis cat
2. Spermatogenesis rat testis
3. Sperm semear human
4. Ovary mature follicle cat…
5. Ovary corpus luteum of…
6. Lillium anther, Late prophase I
7. Lillium anther, First meiotic division – Metaphase I
8. Lillium anther, Second meiotic division
9. Lillium anther, Pollen tetrads
10. Lillium ovary, mother cell – condensation & structure of mother cell
11. Lillium ovary, binucleate stage
12. Lillium ovary,four nucleate stage
• Microslides from mitosis and posters for mitosis and meiosis.
• Compare differences between mitosis and meiosis!
Can you answer them all?
‰ Can you tell the selected volume of a micropipetter?
‰ Can you tell how molecules move in the gel?
‰ What kind of molecules can be isolated by the gel electrophoresis?
‰ Purpose and location of meiosis?
‰ Can you define all words listed above?
‰ Can you replicate the figure 14.2, 14.3 14.4, and 14.5 without any help?
‰ Can you answer questions above on this handout?
‰ Can you answer questions on the text?