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• Germ Cells and
Fertilization
– Sperm Are Highly
Adapted for Delivering
Their DNA to an Egg
• Flagellum
• No ribosomes, ER or
Golgi apparatus.
• Many mitochondria
• Head and tail regions
• DNA is highly packed
to minimize space.
• No transcription
1
• Germ Cells and
Fertilization
– Acrosomal vesicle and
its enzymes for
penetrating the egg coat.
– Acrosomal Reaction:
may help bind the sperm
to the egg coat by
exposing proteins.
2
Flagellum extends from the
basal body
Axoneme: the configuration
of 9 + 2 or 9 doublets of
microtubules and 2 central
single MTs.
Sperm surround their
flagellum with 9 dense outer
fibers. Role?
Movement is caused by
dynein motor proteins and
ATP that slide the
microtubules.
ATP come from all the
mitochondria in the
midpiece.
3
Sperm Production is
Continual in Most Mammals
Spermatogenesis vs.
Oogenesis
Oogenesis: oogonia
proliferate in the fetus, enter
meiosis before birth and will
remain arrested in
development for up to 50
years; number is limited;
released “one at a time.”
Spermatogenesis: sperm
begin development in testes at
puberty and in the
seminiferous tubules
4
From seminiferous
tubules to the
epididymis for
maturation and
storage.
5
Testosterone
secretion
6
Cytoplasmic Bridges: sharing
of cytoplasm; so a Y
spermatid can share its
proteins, etc. encoded by
genes on the X chromosome.
Later the cytoplasm is
discarded.
DAZ Gene on Y: regulates
spermatogenesis; codes for an
RNA-binding protein that
functions in translation.
DAZ gene is deleted in many
infertile men.
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