The first week of human development begins with fertilization of the egg (oocyte) by sperm forming
the zygote. Both the oocyte and sperm have to have half the DNA (haploid) to forn the zygote (diploid). This is achieved by a special form of cell division that only occurs in species that undergo sexual reproduction, meiosis.
Meiosis differs from mitosis in that the cells produced have recombuned their DNA and only contain half the normal cell's DNA content and recomThese notes also cover events
before fertilization formation of both the egg and
sperm, gametogenesis. Cell division can
occur in 2 forms, mitosis and meiosis.
Mitosis can occur in all cells, while meiosis only
occurs during the formation of the sex gametes.
Initially, there is a halving of choromosomal
content in the gametes, which is restored by
fertilization, allowing genetic recombination to
occur. This is then followed by a series of cell
divisions without cytoplasmic growth.
I have also included in the Week 1 notes
information about male sex determination and X
inactivation, which are not really specific to the
first week of development.
Page Links: Introduction | Some Recent Findings | Meiosis Overview |
Differences in Mammalian Meioses |
Polar Bodies |
Comparison of Meiosis/Mitosis |
References | Glossary
Related Pages: Cell division | Mitosis | Gamete Formation | Oogenesis | Spermatogenesis |
Some Recent Findings
Akiyama T, Nagata M, Aoki F.
Inadequate histone deacetylation during oocyte meiosis causes aneuploidy and embryo death in mice. Proc Natl Acad Sci U S A. 2006 May 9;103(19):7339-44.
"It was recently reported that histones are globally deacetylated in mammalian oocytes during meiosis but not mitosis. ...
The high incidence of aneuploidy in the embryos of older females may be due to inadequate meiotic histone deacetylation."
Wang Q, Yin S, Ai JS, Liang CG, Hou Y, Chen DY, Schatten H, Sun QY. Histone deacetylation is required for orderly meiosis. Cell Cycle. 2006 Apr;5(7):766-74.
"The results showed that subcellular translocation, expression level and phosphorylated modification of histone deacetylase 1 were temporally regulated and likely
to coparticipate in the establishment of histone acetylation profiles in oocyte meiosis."
There are several full versions of this content as a lecture available online from UNSW Cell Biology website Medicine- Society and Health , Science- Cell Biology
In female gametogenesis only a single (1) haploid egg is produced from meiosis. In male gametogenesis four (4) haploid sperm are produced from meiosis.
So what happens to all the extra DNA in producing this single egg?
In Meiosis 1 the "extra" DNA is excluded to the periphery as a 1st polar body, which encloses the extra DNA.
In Meiosis 2 the "extra" DNA is once again excluded as a 2nd polar body. The first polar body may also under go meiosis 2 producing a 3rd polar body.
These polar bodies are not gametes.
These polar bodies appear to have no other function than to dispose of the extra DNA.
Comparison of Meiosis/Mitosis
After DNA replication
2 nuclear (and cell) divisions required to produce haploid gametes
Each diploid cell in meiosis produces 4 haploid cells
Each diploid cell mitosis produces 2 diploid cells
only one pair of homologous chromosomes is shown
Occurs when homologues fail to separate
during meiotic division I or II
Caused by an extra copy of chromosome 21.
Chronic myelogenous leukemia
Piece of Chr9 exchanged with Chr22
Generates truncated abl
Overstimulates cell production
Links: Journals | Online Textbooks | Search Textbooks | Reviews |
Articles | 1999 Refs | Search PubMed | Glossary
Molecular Biology of the Cell Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter New York and London: Garland Science; c2002 Meiosis
Developmental Biology Gilbert, Scott F. Sunderland (MA): Sinauer Associates, Inc.; c2000Meiosis
Molecular Cell Biology Lodish, Harvey; Berk, Arnold; Zipursky, S. Lawrence; Matsudaira, Paul; Baltimore, David; Darnell, James E.
New York: W. H. Freeman & Co.; c1999
Search NLM Online Textbooks meiosis
Molecular Biology of the Cell |
The Cell- A molecular Approach
Burgoyne PS, Mahadevaiah SK, Turner JM. The consequences of asynapsis for mammalian meiosis. Nat Rev Genet. 2009 Mar;10(3):207-16. Review.
Location, location, location! Monotremes provide unique insights into the evolution of sex chromosome silencing in mammals.
Daish T, Grützner F.
DNA Cell Biol. 2009 Feb;28(2):91-100. Review.
Maternal origin of the human aneuploidies. Are homolog synapsis and recombination to blame? Notes (learned) from the underbelly.
Garcia-Cruz R, Roig I, Caldés MG.
Genome Dyn. 2009;5:128-36. Review.
Nongenomic steroid-triggered oocyte maturation: Of mice and frogs.
Deng J, Carbajal L, Evaul K, Rasar M, Jamnongjit M, Hammes SR.
Steroids. 2009 Jul;74(7):595-601. Epub 2008 Nov 24.
Kit ligand promotes first polar body extrusion of mouse preovulatory oocytes.
Ye Y, Kawamura K, Sasaki M, Kawamura N, Groenen P, Gelpke MD, Rauch R, Hsueh AJ, Tanaka T.
Reprod Biol Endocrinol. 2009 Apr 3;7(1):26. [Epub ahead of print]
Search Mar 2009 "meiosis" 17,749 reference articles of which 1,873 were reviews.
Search PubMed: term = meiosis
Molecular Biology of the Cell- References
These are a list of references retrieved in a 2000 search of PubMed.(More? meiosis)
- 26 citations found
XL, et al.
- Essential functions of protein tyrosine
phosphatases ptp2 and ptp3 and rim11 tyrosine
phosphorylation in saccharomyces cerevisiae
meiosis and sporulation.
Mol Biol Cell. 2000 Feb;11(2):663-76.
[MEDLINE record in process]
PMID: 10679022; UI: 20143586.
JL, et al.
- Class VI unconventional myosin is required
for spermatogenesis in Drosophila.
Mol Biol Cell. 1999 Dec;10(12):4341-53.
PMID: 10588662; UI: 20056109.
ML, et al.
- Distinct, constitutively active MAPK
phosphatases function in Xenopus oocytes:
implications for p42 MAPK regulation In
Mol Biol Cell. 1999 Nov;10(11):3729-43.
PMID: 10564268; UI: 20032171.
ME, et al.
- Genetic and biochemical characterization of
the yeast spo12 protein.
Mol Biol Cell. 1999 Nov;10(11):3689-703.
PMID: 10564265; UI: 20032168.
PA, et al.
- c-mos and cdc2 cooperate in the
translational activation of fibroblast growth
factor receptor-1 during Xenopus oocyte
Mol Biol Cell. 1999 Nov;10(11):3567-81.
PMID: 10564256; UI: 20032159.
AC, et al.
- A p90(rsk) mutant constitutively interacting
with MAP kinase uncouples MAP kinase from
p34(cdc2)/cyclin B activation in Xenopus
Mol Biol Cell. 1999 Sep;10(9):2971-86.
PMID: 10473640; UI: 99402804.
TJ, et al.
- Multiple sex pheromones and receptors of a
mushroom-producing fungus elicit mating in
Mol Biol Cell. 1999 Aug;10(8):2559-72.
PMID: 10436012; UI: 99365150.
M, et al.
- Architecture of the nuclear periphery of rat
pachytene spermatocytes: distribution of nuclear
envelope proteins in relation to synaptonemal
complex attachment sites.
Mol Biol Cell. 1999 Apr;10(4):1235-45.
PMID: 10198069; UI: 99214008.
E, et al.
- The role of topoisomerase II in meiotic
chromosome condensation and segregation in
Mol Biol Cell. 1998 Oct;9(10):2739-50.
PMID: 9763441; UI: 98437181.
C, et al.
- Differential expression and functions of
cortical myosin IIA and IIB isotypes during
meiotic maturation, fertilization, and mitosis
in mouse oocytes and embryos.
Mol Biol Cell. 1998 Sep;9(9):2509-25.
PMID: 9725909; UI: 98395051.
SA, et al.
- ADP-Ribosylation factors do not activate
yeast phospholipase Ds but are required for
Mol Biol Cell. 1998 Aug;9(8):2025-36.
PMID: 9693364; UI: 98359829.
K, et al.
- Gene Conversion of Major Histocompatibility
Complex Genes in the Mouse Spermatogenesis is a
Mol Biol Cell. 1997 Dec 1;8(12):2511-7.
[Record as supplied by publisher]
JF, et al.
- Polymer models of meiotic and mitotic
Mol Biol Cell. 1997 Nov;8(11):2217-31.
PMID: 9362064; UI: 98028157.
M, et al.
- Protein-protein interactions in the
Mol Biol Cell. 1997 Aug;8(8):1405-14.
PMID: 9285814; UI: 97431777.
LK, et al.
- Drosophila PLUTONIUM protein is a
specialized cell cycle regulator required at the
onset of embryogenesis.
Mol Biol Cell. 1997 Apr;8(4):583-93.
PMID: 9247640; UI: 97390805.
RL, et al.
- cDNA cloning and characterization of a novel
Mol Biol Cell. 1996 Jul;7(7):1015-24.
PMID: 8862517; UI: 97015880.
AO, et al.
- Kinesin-related proteins in the mammalian
testes: candidate motors for meiosis and
Mol Biol Cell. 1996 Feb;7(2):289-305.
PMID: 8688559; UI: 96228687.
MG, et al.
- Organelle-cytoskeletal interactions: actin
mutations inhibit meiosis-dependent
mitochondrial rearrangement in the budding yeast
Mol Biol Cell. 1995 Oct;6(10):1381-96.
PMID: 8573793; UI: 96117051.
J, et al.
- Requirement for phosphorylation of cyclin B1
for Xenopus oocyte maturation.
Mol Biol Cell. 1995 Sep;6(9):1111-24.
PMID: 8534910; UI: 96079260.
C, et al.
- Splicing components are excluded from the
transcriptionally inactive XY body in male
Mol Biol Cell. 1994 Dec;5(12):1341-52.
PMID: 7696714; UI: 95210752.
S, et al.
- The MPM-2 antibody inhibits
mitogen-activated protein kinase activity by
binding to an epitope containing
Mol Biol Cell. 1994 Nov;5(11):1243-51.
PMID: 7532473; UI: 95170120.
AJ, et al.
- Expression and activity of p40MO15, the
catalytic subunit of cdk-activating kinase,
during Xenopus oogenesis and embryogenesis.
Mol Biol Cell. 1994 Aug;5(8):921-32.
PMID: 7803859; UI: 95102156.
KM, et al.
- Mutants at Ser277 of Xenopus cdc2 protein
kinase induce oocyte maturation in the absence
of the positive regulatory phosphorylation site
Mol Biol Cell. 1994 May;5(5):587-96.
PMID: 7919539; UI: 95003216.
S, et al.
- A nuclear factor required for specific
translation of cyclin B may control the timing
of first meiotic cleavage in starfish
Mol Biol Cell. 1993 Dec;4(12):1295-306.
PMID: 7513215; UI: 94220786.
BJ, et al.
- Inositol 1,4,5-trisphosphate mass changes
from fertilization through first cleavage in
Mol Biol Cell. 1993 Apr;4(4):435-43.
PMID: 8507898; UI: 93283738.
MS, et al.
- cdc25+ encodes a protein phosphatase that
Mol Biol Cell. 1992 Jan;3(1):73-84.
PMID: 1312880; UI: 92199341.