Term
| at 3rd week of embryo development, where are primordial germ cells loacted? |
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Definition
| in wall of yolk sac. they will migrate up dorsal mesentery into areas where gonads will develop by 5th week |
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Term
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Definition
condensation of chromatin--> sis chromatids become connected via Rec8p= meisosis specific cohesion complex.
start pairing of homologous chromatids |
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Term
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Definition
| pairing of homologous chromosomes =synapsis: formation of synaptonemal complex, forms a tetrad |
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Term
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Definition
| crossing over of different chromatids |
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Term
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Definition
Condensation still occurs and homologous chrom starts to separate from each other (disjunction).
chiasmata is formed |
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Term
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Definition
| junction btwn chromosomes appears |
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Term
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Definition
| Condensation of chrom. Nucleolus disappears and nuclear membrane disintegrates |
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Term
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Definition
| junction btwn homologous chromosomes |
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Term
| what is reduction division |
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Definition
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Term
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Definition
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Term
| when is somatic # of chromosomes restored? |
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Definition
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Term
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Definition
1) contstancy of chrom #
2) indep assortment of maternal and paternal chromosomes (INC VAR!!)
3) NON disdjunction in |
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Term
| kleinfelter is non disjuntion of which type of chromosome |
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Definition
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Term
Spermatogensis phases
B) what age does it begin
c) how long does it take to occur? |
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Definition
1) spermatogonial
2) spermatocyte phase
3) spermiogensis
B) btwn 13-16
C) 64-74 days |
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Term
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Definition
spermatogonia diff in to primary spermatocytes
TYPE A (stem cells): spermatogonia mitotically divides --> type b spermatogonia (progenitor cells)
Type B- during S phase ->gives rise to prim spermatocyte
TYPE A and B 46c 2n
prim spermatocyte = 46 4n |
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Term
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Definition
46 4n prim spermatocyte will give rise to 2-23 chrom 2n 2ndary spermatocytes
2nd div--> 2 23 c 1n spermatids |
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Term
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Definition
spermatids diff -> spermatozoa
ONLY a change in shape
flagella are formed, nucleas gets smaller, mitochondria line flagella. acrosomal granules --> vesicle-> cap-> acrosome |
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