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31 Cards in this Set

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