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46 Cards in this Set

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Meiosis 1 (reductional division)
Prophase1, Metaphase1, Anaphase 1, Telophase 1
Meisosis 2 (equatorial division)
Prophase 2, metaphase 2, anaphase 2, telophase 2 (like mitosis)
Prophase 1
Tetrads form
chromatin condenses into visible chromosomes
Homologus Paternal and maternal chromosomes pair via synaptonemal complex
Chromosomes condense
Pairing of homologus dyads (prs of sister chromatids)
Synaptonemal complex forms
DNA strands of nonsister chromatids start recombination
Synapsis complete
Recombination nodules appear (at least one for each pair)
Enzymes for DNA combination and repair
Recombination complete
Synaptonemal complex begins to breakdown
Chiasmata appear at recombination nodes, migrate towards end of chromatids
Chromosomes condense further
Metaphase I
Homologous prs of chromosomes align on equatorial plate of spindle
Spindle fibers from either pole attach to kinetochore
Anaphase I
Pair of chromatids separate at centromere
Telophase I
Like mitotic telophase
Each daughter has 23 chromosomes
2 non identical sister chromatids
diploid DNA
Meiosis II
Interphase with no DNA replication
Other steps like mitosis
Daughter cells have 23 chromosomes but a haploid DNA
the failure of chromosomes to correctly separate:
homologues during meiosis I or
sister chromatids during meiosis II
Missing one chromosome
Missing one chromosome
Three of the same chromosome
Lethal, except for 13. 18, and 21 and X
Primordial germ cells (46,2n) testes week 4 of emryogenesis
Type A Spermatogonia – mitosis to produce stem cells
Type B Spermatogonia (46, 2n)  primary spermatocytes (46,4n) --> 2 secondary spermatocytes (23,2n) -->meiosis II  4 spermatids (23, 1n)  sperm (23,1n)
Occurs in female reproductive tract
Unmasking of sperm glycosyltransferases
Removal of surface coat of sperm
Primordial germs cells (46,2n) in ovary week 4 of embryogenesis oogonia (46,2n)meiosis I  primary oocytes (46,4n) all formed by 5th month of fetal life, remain in diplotene of prophase until puberty
Secondary oocyte (23, 2n) and 1st polar body formed during ovarian cycle
Enters meiosis II and ovulation occurs at metaphase, remain there until fertilization  mature oocyte (23,1n) and 2nd polar body formed after fertilization
Ovarian Cycle
Hypothalamus  GNRH  adenohypophysis  FSH & LH
FSH2° follicle graafian follicle within the ovary
Granulosa cells of 2° and graafian follicle  estrogen
Estrogen  endometrium enters proliferative phase
Granulose lutein cells of corpus luteum  progesterone  endometrium into secretory phase
Menstrual Cycle
1) 1-4 menstruation  necrosis and shedding of endometrium
2) 4-15  proliferative phase  regeneration of functional layer of endometrium, low basal body temperature (97.5°F)
3)14-16 ovulatory phase  ovulation of 2° oocyte and ↑ LH
4) 15-25  secretory phase  endometrial gland secretion, body temp ↑98° implantation occurs
5) 25-28  premenstrual phase  ischemia due to reduced blood flow to endometrium
Acrosomal Reaction
Sperm binds to zona pellucida of 2° oocyte releasing acrosomal enzymes  penetration of ZP  cortical reaction  2° oocyte impermeable to other sperm
Male Pronucleus
Nucleus of the sperm
No tail or mitochondria from sperm
Female Pronucleus
Nucleus of the ovum
Male and female pronucleus fuse to form zygote
Series of mitotic divisions of zygote
Zygote blastula  morula (32 cell stage)
32 cell stage
Inner cell mass
Outer cell mass
Mitotically dividing zygote cells,
Totipotent til 8 cell stage (can form whole new embryo)
Blastocyst Formation
Morula secretes blastocyst cavity
Inner cell mass that becomes the embryo
Outer cell mass becomes part of the placenta
embryoblast gives rise to bilaminar embryonic disk
epiblast --> amniotic cavity
hypoblast --> yolk sac
prochordal plate
fusion of epiblast and hypoblast cells
marks future site of mouth
grows into endometrium to contact blood vessels and glands
not divide mitotically
produces HCG (human chorionic gonadotropin)
divides mitotically
primary chorionic villi protrude into the syncytiotrophoblast
extraembryonic mesoderm
derived from epiblast
extraembryonic somatic mesoderm
lines cytotrophoblast
aka somatopleuric mesoderm
forms connecting stalk (suspends within chorionic cavity)
covers amnion
Wall of the chorionic cavity
1. extraembryonic somatic mesoderm
2. cytotrophoblast
3. syncytiotrophoblast
extraembryonic visceral mesoderm
splanchnopleuric mesoderm
Human Chorionic Gonadotropin (HCG)
syncytiotrophoblast produces HCG
stimulates progesterone by corupus luteum (maintains function)
luteal progesterone needed for maintenence of pregnancy til week 8 when placenta takes over
-Day 8 in maternal blood, day 10 in urine (pregnancy testing)
low HCG --> miscarriage or ectopic
high HCG --> multiple pregnancy or other problems
week 3
Germ layers
ectoderm --> epidermis, nervous system
endoderm --> GI tract and organs, respiratory passages and organs
mesoderm--> muscles, connective tissue
formation of primitive streak, notochord, germ layers
primitive streak
thickened band of epiblast cells, appears caudally in the midline of embryonic disk
primitive knot (Hansen's Node)
cranial end of embryonic disk
epiblast cells multiply and migrate towards the primitive streak then through its groove
spread laterally and cranially to form intraembryonic mesoderm between epiblast and hypoblast