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31 Cards in this Set
- Front
- Back
When does human development begin?
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At fertilization
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What is a zygote?
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The single cell resulting from union of a sperm with oocyte.
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What is the gestational age calculated from?
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The LNMP - approx. 14 days before development/conception ACTUALLY begins.
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How much genetic material do the sperm/oocyte contain?
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Half the normal amt; HAPLOID
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What is the normal amt of genetic material in somatic cells?
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46N - one set of chromosomes from each parent.
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When are sperm/ova produced?
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During gametogenesis.
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What causes the decrease in DNA in gametes?
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Meiotic division
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What is gametogenesis?
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the process of forming and developing specialized generative cells, involves chromosomes and gamete cytoplasm.
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What occurs during gametogenesis?
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-Reduction of chromosome number by half
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What is meiosis?
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Special cell division involving 2 meiotic cell divisions.
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What cells undergo meiosis?
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Only germ cells.
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What is the first meiotic division in germ cells?
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Reduction division - diploid -> haploid, 2N (homologs are diploid chromatids)
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How does the chromosome number get halved during 1st meiotic division?
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The number of CHROMOSOMES is halved, but the chromatids are diploid.
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How does meiosis II produce 4 haploid 1N cells?
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No replication occurs prior to division.
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What is nondisjunction?
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Disturbance of meiosis during gametogenesis.
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What results from nondisjunction?
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formation of chromosomally abnormal gametes.
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What is spermatogenesis exactly?
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Sequence of events where spermatogonia mature into spermatozoa.
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When does spermatogenesis begin in males?
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At puberty
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What are spermatogonia?
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Dormant germ cells in the seminiferous tubules of testes; there since fetal period.
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How do spermatogonia get ready for spermiogenesis?
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Increase in number (by mitosis) at puberty onset.
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What are primary spermatocytes?
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Spermatogonia that have grown and undergone changes to get ready for spermatogenesis; the largest germ cells in the seminif. tubules.
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What happens to spermatocytes?
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Meiosis - division 1 (reduction) and 2.
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What does Meiosis one produce?
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2 secondary SPERMATOCYTES - half the size of the primary spermatocyte.
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What does Meiosis two produce?
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4 haploid SPERMATIDS, each 1/2 the size of 2ndary cells.
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What is spermiogenesis?
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The maturation of spermatids into mature sperm.
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How long does spermatogenesis (including spermiogen) take?
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approx. 2 months
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What are the support cells in seminiferous tubules?
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Sertoli cells
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Where are mature sperm stored?
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In the epididymus
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What does a mature sperm consist of?
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-Head
-Tail -Neck |
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What is the structure of the sperm head like?
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-Contains haploid nucleus
-Acrosome covers anterior 2/3 |
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What is the acrosome?
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Sac organelle containing enzymes to facilitate penetration of corona radiata and ZP of the ovum.
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