Fertilization Flashcards
Outcomes of gametogenesis
Mature gametes are produced by meiosis and maturation. Genetic diversity is achieved by crossover and independent assortment of genes and random distribution of mom and dad chromosomes
mRNAs carrying information for continued development of the gametes are stored in the cytoplasm
Sperm
designed to be mobile, penetrate, and deliver paternal genome
Theres a head and tail on the head there are 3 layers of membranes, PM, outer and inner acrosome
2 vvarieties of sperm. X and Y
Ovulated oocyte
designed for supporting and sustaining embryo development
Stores important compunds in cytoplasm
divides after diploid chromosome is restored
Has seeral coverings in to out (cortical granule, cortex, oocyte PM, perivitaline space, zona pellucida Z1234)
Production of abnormal gametes
Morphological abnormalities- affect sperm and oocytes
Chromosomal abnormalities- nondisjuction in meiosis, translocation, deletions, fresh gene mutations
advanced parental age-
Where does fertilization occur
only a few hundred sperm make it to the site of fertilization, oocytes viable for 1 day, sper 3-5 days
Journey of sperm- epididymis, vas, urethra, vagina, cervix, uterus, isthmus
Mucus low pH sperm antibodies can affect the sperms journey
Presence of cumulus cells appears critical for oocyte pickup- cumulus cells around oocyte
Fertilization is a multistep process- both gametes have a role (
Fertilization: Step 1 Capacitation
Occurs in female fluids, sperm membrane changes, increased sperm metabolism, sperm become hypermobile
The oocyte produce sperm chemotrophic factor, only capacitated bind to oocyte
Fertilization: Step 2, Acrosome Rx
when sperm is in the cumulus, acrosome enzymes are exposed, Ca mediated signaling
Fertilization: Step 3, Sperm binds to zona pellucida
sperm receptors bind to ZP 2 and 3
Sperm ligand is a membrane protein (SED1)
Fertilization: Step 4, Zona pellucida penetration
acrosome enzymes and sperm wiggles in
Fertilization: Step 5, sperm oocyte fusion
fusion at equatorial region of sperm
Sperm -fertilin B and oocyte integrin interact, only acrosome Rx sperm can fuse with oocyte
Sperm gets incorporated
Fertilization: Step 6, Oocyte activation
Ca Oscillation, cortical Rxn, Zona Rxn, Meiosis gets completed M and F pronuclei
Poly spermy is prevented by: Ca oscillations and cortex and Zona rxns
Finally a zygote is made
Results of fertilization
Oocyte completes meiosis
Restoration of diploid chromosome number
Genetic sex determined, cleavage initiated
Both parents are needed for embryonic development (genomic imprinting) ie you cant take two oocytes
Imprinting occurs during gametogenisis
