C4: Fertilization Flashcards
process in which gametes (an egg and sperm) fuse to form a zygote
Fertilization
the egg and sperm are ___, which means they each contain one set of chromosomes; upon fertilization, they will combine their genetic material to form a zygote that is ___, having two sets of chromosomes
haploid; diploid
zygote that has more than two sets of chromosomes will not be ___
viable
the combining of genes derived from two parents
sex
the generation of a new organism
reproduction
fertilization accomplishes two separate ends
sex; reproduction
occurs when proteins on the sperm cell membrane meet proteins on the extracellular coating of the egg
sperm-egg recognition
the sperm cell membrane is altered significantly by ___ events activated by the __
exocytotic; egg
once inside the egg, the sperm activates development by causing the release of ____ from within the egg
calcium ions (Ca2+)
these ions stimulate the enzymes needed for DNA synthesis, RNA synthesis, protein synthesis, and cell division
calcium ions (Ca2+)
in ___ plants, several nuclei are involved in fertilization
angiosperm
Four major events of fertilization:
1.) Contact and recognition between sperm and egg
2.) Regulation of sperm entry into the egg
3.)Fusion of the genetic material of sperm and egg.
4.)Activation of egg metabolism to start development.
Which fetilization event?
-In most cases, this ensures that the sperm and egg are of the same species.
1.) Contact and recognition between sperm and egg
Which fetilization event?
Only one sperm nucleus can ultimately unite with the egg nucleus. This is usually accomplished by allowing only one sperm to enter the egg and actively inhibiting any others from entering.
2.) Regulation of sperm entry into the egg.
Significance of Fertilization (8)
1.) stimulates the secondary oocyte to undergo second maturation division to release second polar body and to form haploid ovum
2.) restores the diploidy in the zygote
3.) Fertilization membrane prevents the polyspermy
4.) Metabolic activities are increased as more mitochondria are available
5.) combines the characters of two parents and introduces variations
6.) Centrioles of sperm from the spindle to initiate the cleavage of zygote
7.) Sex chromosome of sperm is either X or Y and helps in sex determination
8.) Copulation path sets the axis of division
Sequential Events of Fertilization (9)
- Penetration of the corona radiata
- Attachment to the zona pellucida
- Acrosomal reaction and penetration of the zona pellucida
- Binding and fusion of sperm and egg
- Prevention of polyspermy
- Metabolic activation of the egg
- Decondensation of the sperm nucleus
- Completion of meiosis in the egg
- Development and fusion of male and female pronuclei
when the spermatozoa first encounter the ovulated egg in the ___ of the uterine tube, they are confronted by the ___ and some remnants of the ___, which represents the outer layer of the egg complex
ampullary part;
corona radiata;
cumulus oophorus
___ is a highly cellular layer with an __ matrix consisting of proteins and a high concentration of carbohydrates (especially ___)
corona radiata;
intercellular;
hyaluronic acid
It is widely believed that ___ emanating from the sperm head plays a major role in penetration of the corona radiata
hyaluronidase
the ___, which is __ µm in humans, consists principally of four ____combine to form basic units that polymerize into long filaments
zona pellucida; 13;
glycoproteins (ZP1 to ZP4. ZP2 and ZP3)
spermatozoa bind specifically to a ___ molecule, which is the __ part of a sequence of four sugars at the end of O-linked ___ that are attached to the polypeptide core of the __ molecule
sialic acid;
terminal;
oligosaccharides;
ZP3
molecules on the surface of the sperm heads are specific binding sites for the __ sperm receptors on the ___
ZP3;
zona pellucida
___ in the ___ regions of the __ molecule may serve as the basis for the inability of spermatozoa of one species to fertilize an
egg of another species.
Interspecies molecular differences; sperm-binding;
ZP3
the essence of the __ is the fusion of parts of the outer acrosomal membrane with the overlying plasma membrane and the pinching off of fused parts as small vesicles
▪ this results in the liberation of the multitude of enzymes that are stored in the ___
acrosomal reaction;
acrosome
acrosome of sperm undergoes acrosomal reaction and releases certain ___ which dissolve the egg envelopes locally and make the path for the penetration of sperm
sperm lysins
__ are acidic proteins that contain a lysing enzyme ___ which dissolves the hyaluronic acid polymers in the intercellular spaces which holds the granulosa cells of corona radiata together
sperm lysins;
hyaluronidase
most important enzyme (which dissolves the zona pellucida
acrosin or Zona lysin
in humans, there is always ___
monospermy
space between the egg’s plasma membrane and the zona pellucida
perivitelline space
binding between the spermatozoon and egg occurs when the ___ of the sperm head contacts the ___ surrounding the egg
equatorial region;
microvilli
molecules on the plasma membrane of the sperm head, principally sperm proteins called __ and __, bind to __ and ___ molecules on the surface of the egg
fertilins and cyritestin;
α6 integrin and CD9 protein
the ___ causes a change in the membrane properties of the spermatozoon
acrosomal reaction
actual fusion between spermatozoon and egg, mediated by ___ on the membrane of the oocyte, brings their plasma membranes into continuity
integrin
the ___ to polyspermy, which has been best studied in ____, consists of a rapid ___ of the plasma membrane of the egg
▪ the resting membrane potential of the egg changes from about ___ to ___ within __ to ___ seconds after fusion of the spermatozoon with the egg
fast block;
sea urchins;
electrical depolarization;
−70 to +10 mV;
2 to 3
the ___, spreading from the site of sperm-egg fusion, is involved in stimulating completion of the second meiotic division of the egg
first set of waves (of Ca++)
____ initiate recruitment of maternal RNAs in the egg and act on the cortical granules as they pass by them
later waves of Ca++
exposure to Ca++ causes the ___ to fuse with the plasma membrane and to release their contents (__ and __) into the ___
cortical granules;
hydrolytic enzymes and polysaccharides;
perivitelline space
the ___ released into the ____ become hydrated and swell, thus causing the ___ to rise from the surface of the egg
polysaccharides;
perivitelline space;
zona pellucida
___ essentially eliminates the ability of spermatozoa to adhere to and penetrate the zona
zona reaction
the sperm introduces into the egg a soluble factor (currently thought to be a _____]), which stimulates a pathway leading to the release of pulses of Ca++ within the cytoplasm of the egg
phospholipase [phospholipase C zeta]
▪ in addition to initiating the blocks to polyspermy, the released Ca++ stimulates a rapid intensification of the egg’s respiration and metabolism through an exchange of ____ for ___
extracellular Na+;
intracellular H+
exchange of extracellular Na+ for intracellular H+ results in a rise in ____ and an increase in ___
intracellular pH;
oxidative metabolism
in mature spermatozoon, the nuclear chromatin is very tightly packed, in large part because of the _______ that occurs among the ___ molecules complexed with the DNA during ___
—SS— (disulfide) cross-linking;
protamine;
spermatogenesis
shortly after the head of the sperm enters the cytoplasm of the egg, the permeability of its ___ membrane begins to ___, thereby allowing ___within the egg to affect the nuclear contents of the sperm
nuclear;
increase;
cytoplasmic factors ;
after ___ of the —SS— cross-links of the protamines to ____ by reduced __ in the ___, the ___ are rapidly lost from the chromatin of the spermatozoon, and the chromatin begins to spread out within the nucleus (now called a pronucleus) as it moves closer to the nuclear material of the egg
reduction;
sulfhydryl (—SH) groups;
glutathione; ooplasm;
protamines;
it takes about __ hours for the remodeling of the sperm
6 to 8
after a short period during which the male chromosomes are naked, ___ begin to associate with the chromosomes
histones
during the period of ___, the genetic material of the male pronucleus becomes ___, whereas __ in the female genome is maintained
pronuclear formation;
demethylated;
methylation
after penetration of the egg by the spermatozoon, the ___ of the egg, which had been arrested in ___ of the second meiotic division, completes the last division and releases a ___ into the ___
nucleus; metaphase;
second polar body;
perivitelline space
the nucleus of the oocyte moves toward the __ as the result of the action of ___ molecules acting on a network of ___ that connect one pole of the ___ to the cortex
cortex;
myosin;
actin filaments;
mitotic spindle
a ___, derived largely from the endoplasmic reticulum (ER) of the egg, forms around the female chromosomal material
pronuclear membrane;
____ seem to control the growth of the female and the male pronuclei
cytoplasmic factors
pronuclei appear ___ hours after sperm penetration, and they persist for about ____ hours
6 to 8;
10 to 12
___ occurs in the developing __ pronuclei, and each chromosome forms ___ as the pronuclei approach each other
DNA replication;
haploid;
two chromatids
Parthenogenesis came from Greek words, parthenos which means “__” and genesis meaning “__”
virgin;
birth
natural form of asexual reproduction in which growth and development of embryos occur without fertilization
Parthenogenesis
___ is when an ovum is activated in the absence of sperm
parthenogenesis
in ___, parthenogenesis means development of an embryo from an unfertilized egg cell while in ___, parthenogenesis is a component process of apomixis
animals;
plants
asexual seed formation
apomixis
it is one in which the egg cell is produced through mitosis then develops directly into an embryo without the prior fertilization
apomictic parthenogenesis
this type of reproduction has been induced artificially in a few species including fish and amphibians
parthenogenesis
haploid individuals, however, are usually __, and ___ usually have the diploid chromosome number
non-viable;
parthenogenetic offspring
depending on the mechanism involved in restoring the diploid number of chromosomes, parthenogenetic offspring may have anywhere between all and __ of the mother’s __
half; alleles
the offspring having all of the mother’s genetic material are called ___ and those having only half are called __
full clones;
half clones
these offsprings are usually formed without meiosis
full clones
women who do not ovulate
anovulatory
a nonsteroidal antiestrogen that suppresses the normal negative feedback by estrogens on gonadotropin production by the ptiuitary
clomiphene citrate
too few spermatozoa
oligospermia
the method of ___ has resulted in slightly higher percentage of pregnancies than the standard in vitro fertilization and embryo transfer methods
gamete intrafallopian transfer (GIFT)
in this variant, a cleaving embryo that has been produced by in vitro fertilization is implanted into the uterine tube
zygote intrafallopian transfer (ZIFT)
