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31 Cards in this Set
- Front
- Back
Interphase
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Nuclear envelope intact
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Prophase
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- Chromosomes condense and become visible
-Bipolar spindle develops |
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Prometaphase
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-Nuclear envelope dissolves
-Chromosomes BEGIN to migrate to equatorial plane (metaphase plate) -Have two sister Chromatids! |
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Metaphase
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Chromosomes fully condense and located at metaphase plate
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Anaphase
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-Each centromere splits
- Two chromatids are pulled to opposite polls |
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Teleophase
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-Chromosomes reach poles and start toe decondense
-Nuclear membrane reforms -Cytoplasm starts to divide |
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Mitotic Non disjunction
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Abnormal chromosome segregation in rapidly dividing tissues
Seen in Leukemia |
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Meosis 1 (general)
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-Reduction Division
-Chromosome number halved via pairing of homologous chromosomes- (segregated at Anaphase 1) -Cross over here (Pachytene) - Meiotic non disjunction can happen here leading to meiotic non-disjunction -Start: 2n4c -End: 1n2c |
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Meiosis 2 (General)
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-No additional DNA replication
-CHROMATIDS seperate -One chromatids remain in each gamete -Start-1n2c -End 1n1c -Haploid -4 games result -23 nonidentical chromosomes in each gamete |
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Meiosis Prophase 1
Leptotene |
Sister Chromatids hanging out- not paired with there homologous analogs yet
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Meiosis Prophase 1
Zygotene |
-Sister Chromatids find there homologous analog
-These pair together and form BIVALENTS |
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Meiosis Prophase 1
Pachytene |
-Crossing over happens here
-Chromosomes Thicken |
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Dipotene
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-Homologous pairs start to pull apart but are held together by chiasmata
-Easy to view and count cross pairing here |
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Meiosis Prophase 1
Diakinesis |
Bivalents are more contracted
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Metaphase 1
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-Nuclear membrane disappears
-Spindle forms -Paired chromosomes align at equatorial plane with centromeres oriented toward different poles |
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Anaphase 1
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Bivalents seperate
Disjunction (sister chromatids are drawn to opposite poles) Cell becomes haploid |
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Telophase 1
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Haploid chromosomes cluster at opposite pols
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Cytokinesis
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2 haploid cells form then enters meiotic interphase
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Primordial oocyte
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Original cell for germline
Makes 22 mitotic divisions Primary oocyte enters meiosis 1 |
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Primary oocyte
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2^22 of these
Enters Meiosis 1 at prophase Suspended until ovulation |
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Polar Body
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After Meiosis 1- one of the gametes sequesters most of the cellular contents. As a result you have one cell that is a regular gamete and one that is a polar body. The polar body makes two more polar bodies in Meiosis 2. The regular gamete makes a regular cell and another polar body.
http://www.youtube.com/watch?v=eqHRDAnUrGY |
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Mature oocyte
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Ready to go
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Male Gametogenesis
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Continuous throughout life
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Spermatogonia
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- an undifferentiated male germ cell, originating in a seminiferous tubule and dividing into two primary spermatocytes
- 30 division in fetal growth and childhood until puterty - 20-25 replications per year after |
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Primary Spermatocyte
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-a diploid cell that has derived from a spermatogonium and can subsequently begin meiosis and divide into two haploid secondary spermatocytes.
-Start meiosis 1 with this |
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Secondary Spermocyte
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-one of the two haploid cells into which a primary spermatocyte divides, and which in turn gives origin to spermatids.
-Start Meiosis 2 with this |
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Spermatid
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Final Gametes of spermatogensis
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Meiotic Nondisjunction
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-Theory: The longer oocytes have to stay in Meiosis, the more stress it endures and the more likely it will cause a disjunction error
-13,18,21, and 47XX autosomal trisomies are maternal germline errors 80-100% of the time |
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Nondisjunction at Meiosis 1
Results |
n+1
n+1 n-1 n-1 |
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Nondisjunction at Meiosis 2
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n
n n-1 n+1 |
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Down syndrome (number)
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Trisomy 21
92% materrnal (75% at meiosis 1--25% at meiosis 2) 8% paternal |