Gametogenesis

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Craig Venter, the American scientist whose
company mapped a private version of the human
genome has finished decoding his DNA, which would
make him the first person on the planet able to
read, if not fully understand, his own operating
instructions.
Craig Venter
The completed sequence of the human genome was
published in February 2001 in the journal,
Science 99 of gene-containing part of human
sequence finished to 99.99 accuracy. In addition
to the human genome, Venter and his team at
Celera sequenced the fruit fly, mouse, and rat
genomes.
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2006/2007
The National Institutes of Health (NIH) has
developed the database of Genotype and
Phenotype dbGaP, a newdatabase designed to
archive and distribute data from genome wide
association (GWA) studies. GWA studies explore
the association between specific genes (genotype
information) and observable traits, such as
blood pressure and weight,or the presence or
absence of a disease or condition (phenotype
information).
European Researchers Team Up to Probe Genetic,
Environmental Links in Dyslexia
Sea urchin genome suprisingly similar to man and
may hold key to cures The purple sea urchin, in
fact, has 7,000 genes in common with humans,
including genes associated with Parkinsons,
Alzheimers and Huntingtons diseases and
muscular dystrophy.
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Researchers to map pig DNA Friday, January 20,
2006 Posted 947 a.m. EST (1447 GMT)
CHAMPAIGN, Illinois (AP) -- A team of
researchers won a 10 million federal grant to
provide the first complete sequence of the swine
genome -- a genetic map they say could help
farmers produce better hogs, give consumers
tastier pork and ultimately benefit human
health.
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Leptotene DNA replication
Zyogotene pairing of homologues
Pachytene crossing over
Diplotene RNA transcription
Meiosis I
Meiosis II
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Gametogenesis
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Diploid genome / 2 X amount of DNA
Diploid genome / 4 X amount of DNA
Meiosis I
Haploid genome / 2 X amount of DNA
Meiosis II
Haploid genome / 1 X Amount of DNA
4 1
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Diploid pool of oogonia
Fig. 19.25, pg. 617
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Diploid pool of oogonia
Fig. 19.25, pg. 617
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Vitellogenin yolk material synthesized in
telolecithalic eggs (amphibians/reptiles/birds)
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Previtellogenesis Vitellogenesis
Fig. 19.28, pg. 619
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Gene amplification Repeated gene sequences
which are produced in certain cells at
certain stages of development - Not inheritable
Gene replication Repeated sequences within all
cells that are inheritable
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Previtellogenesis Vitellogenesis
Fig. 19.28, pg. 619
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DNA
RNA
Pg. 618
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1,800 copies of 18S 28S rRNA genes amplified to
gt 500,000 copies during diplotene stage of
meiosis I
gt 1012 ribosomes synthesized in the egg
Pg. 636
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Products Synthesized During Oogenesis

• rRNA transcribed 18S, 28S 5S RNA and
• 60 proteins

• tRNA transcribed 45 of total RNA

• Proteases and hyaline proteins for use
• at fertilization

• Vg1 protein transcription but not translation
• (paracrine growth factor)

• Maternal mRNAs for 1st cleavages

• Maternal mRNAs for vitellogenesis

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Ribosomes Glycoproteins ER
o
AP
o
FSH
o
o
o
o
VP
Mitochondria 100,000/oocyte
ESTROGEN
E2 stabilizes vitellogenin mRNA for accumulation
over 3 weeks
Cortical granules
Proteolytic enzymes Mucopolysaccharides
Hyaline proteins
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Cytoskeletal Pathway
3 untranslated region
Vg1 mRNA
350 bases
Vera protein
ER vesicles
Microtubules (tubulin)
Anchored in cytoskeletal cortex by microfilaments
Message transport organizer Pathway
messages leave germinal vesicle and join
mitochondrial cloud
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Cytoskeleton
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Glycocalyx
One cells component of a Gap Junction
Hormone receptors
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High FSH/ Low LH
Granulosa cells
Oocyte
Gap Junctions
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High FSH/ Low LH
Granulosa cells
Oocyte
cAMP
Gap Junctions
cAMP
Inactive cAMP-dependent protein kinase
Active cAMP-dependent protein kinase
ATP
ADP
Non-phosphorylated proteins (inactive)
Phosphorylated proteins (active)
Phosphorylase kinase
Maintain Meiotic Arrest
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elevated LH
Downregulation of Cx43 expression and induction
of conformational changes
Hyaluronic acid
X
cAMP
Inactive cAMP-dependent protein kinase
X
Active cAMP-dependent protein kinase
ATP
ADP
X
Non-phosphorylated proteins (inactive)
Phosphorylated proteins (active)
X
Phosphorylase kinase
X
Renewed Meiosis
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FSH
cAMP-mediated 2nd messenger system
FSH receptors
LH
_
LH Receptors

Estrogen
- Follicular Maturation - Oocyte nucleus
remains in meiotic arrest in Diplotene
stage of Meiosis I
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1st Polar body
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Spermatogenesis
Homunculus
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Spermatogenesis
Fig. 19.22, pg. 614
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Dynein protein - Attached to
microtubules - Involved in hydrolyzing ATP to
supply energy for motility
Nucleus
Mitochondria
Acrosome Proteolytic enzymes Egg
recognition proteins
Spermatozoan
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Pulse/Chase Experiment
Darnell et al. pg. 193
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3H-Uridine labeled RNA in multinucleated cell
Autoradiography
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Tubulin proteins Bindin
Protamines ß-galactosyltransferase
Pronases
Haploid gene Expression - mRNAs translated
after fertilization
MEIOSIS I Diplotene
MEIOSIS II
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Histones - structural proteins - highly
charged to bind tightly to DNA and pack it
in to nucleosome units

• Protamines
• replace histones
• more highly
• charged and allow
• for more dense
• packaging

Protamine mRNA synthesized _at_ primary
spermatocyte stage Stored and then translated
at spermatid stage during storage other mRNAs
translated
Chromatin
Pg. 102
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Regulatory Mechanisms to Date

• Gene amplification (vs. gene replication)
• Hormones (changing concentrations /-
  feedback)
• Hormone receptors (presence/absence/concentrati
  ons)
• Up/down regulation of gene expression
• Gap junctions (cAMP)
• Allosteric regulation of enzyme activity
• Paracrine control (hormones/gap junctions)
• Stabilization of mRNAs
• Turnover rates (half life)
• Presynthesis of mRNA (transcription) and
  storage
• for later translation (unequal
  positional storage)