In the process of sexual reproduction of organisms, sperm and egg cells usually together, to develop into a new individual. The fusion of sperm and egg into fertilized eggs, called fertilization. In the fertilization, usually is the head of the sperm into the egg cell. The tail was left outside. Then, outside the egg cell membrane appeared a special membrane, to prevent other sperm to enter. Near the head of the sperm into the egg cell, inside the nuclei and meet the nucleus of an egg cell, make each other's experience of staining together. In this way, the chromosome number of the fertilized eggs and restored to the number of somatic cells, of which half of the chromosome from the sperm (father), the other half from the egg cell (the mother).
The two types of haploid
Eggs and fusion of sperm and egg, the fertilization, re formation of a diploid
The cell, the fertilized egg. In mammals, birds, reptiles, fertilization occurs in the female animal. reproductive system
Amphibians, fish and invertebrates, fertilization in vitro. Whatever the case, the fertilization are basically the same process: the contact between sperm and egg, sperm egg by penetration, sperm egg membrane fusion, egg activation. Including the reaction: Acrosome reaction
(acrosomal reaction), Cortical reaction
(cortical reaction), Prokaryotic fusion
Fertilization The process of fertilization
The fertilization process consists of 5 stages:
1, through the sperm Radiata
2, through the sperm Transparent tape
3, the sperm into the egg cell membrane (1) Cortical response
(2) the egg cell membrane blocking effect (3) Zona reaction
Effect of different fertilization and sexual reproduction:
Fertilization is a process of sexual reproduction is a kind of reproductive mode. They can't be equal to.
The definition of sexual reproduction:
The parents have sex germ cell
(gametes), after sexual cells (e.g. sperm and egg cells) combination (such as eggs) become a zygote, the zygote has become a new individual reproductive mode called sexual reproduction.
Sexual reproduction is combined by germ cell reproduction.
In the process of sexual reproduction of organisms, sperm and egg cells usually together, to develop into a new individual. The fusion of sperm and egg into fertilized eggs, called fertilization.
Fertilization is Egg
The fusion is a process of the zygote. It is sexual reproduction
The basic characteristics, widely exists in animal and plant community.
Usually, only one sperm into the fertilized eggs, said Monospermy
Such as animal, Echinodermata, coelenterate animal, part animal, bony fish, amphibians and mammals animal. This kind of egg and sperm once contact, immediately be activated and produce a series of changes, to prevent other sperm into the egg. If the egg is not appropriate because the degree of maturity and other reasons, and there are more than one sperm into the egg, the so-called pathological Polyspermia
Then, the cleavage is not normal, embryo deformity, sooner or later will die of shame. Some eggs in the normal fertilization conditions, there may be more than one sperm enters the egg, but only one of the original male sperm nuclear and egg pronuclei of zygotes, become the nucleus, the rest of the sperm gradually disappear, called physiologic polyspermy. Such as insects, soft animal, fish cartilage, amphibians, reptiles and birds.
Fertilization The sperm acrosome reaction
Many known mammalian sperm through the female reproductive tract or through Cumulus
When the package of sperm exogenous protein was cleared, physicochemical and biological characteristics of sperm membrane changes, so that Sperm capacitation
In the process of fertilization.
Sperm egg contact week Egg membrane
or Transparent tape
When a specific and egg membrane. glycoprotein
Combined excitation of sperm production Acrosome reaction
Lost on the plasma membrane of acrosome outer periphery of the outer acrosomal membrane invagination, vesicles, including some of the contents in the top hydrolase
Exo. The top of the body
The reaction is helpful to further sperm through the egg membrane. In the sea urchin eggs, sperm acrosome reaction is a perivitelline film in polysaccharides provoked. Most of the eggs are eggs peripheral membrane, a variety of different thickness of egg membrane, the main component is mucin or mucopolysaccharide; only a few are naked eggs, such as animal coelenterate eggs.
Sperm through the egg membrane, after combining the first adhesion process. The former is a loose attachment, without outside interference temperature, specificity, no adhesion during the acrosome membrane. Acroblast
Protein into acrosomal protein, acrosomal protein accelerated through sperm Egg membrane
The role of the latter; is firmly combined by low temperature interference, is species specificity. In the sea urchin sperm plasma membrane
Have isolated a can with egg membrane glycoprotein
Specific binding protein, called binding protein, molecular weight of about 30000.
Fertilization Egg activation
Once the sperm and egg, the egg is also activated a series of changes. In mammalian eggs, showed response to the cortex, egg plasma membrane
Reaction and Zona reaction
And thus play a role in blocking the fertilized egg and stimulate further development of the. Cortex in response to fine Egg cell
Fusion of the fusion point, since the beginning of, Cortical granule
The rupture. Inclusion
Efflux, which affected the whole egg cortex. Egg membrane reactor is the recombination process of egg quality and cortical granule capsule. Zona reaction for cortical granule efflux formed together with transparent tape Fertilization membrane
The process of separating egg membrane and plasma membrane, the zona pellucida sperm receptor disappeared, zona hardening.
Fertilization Sperm egg fusion
Sperm oocyte fusion can first see the egg microvilli surrounded by sperm may play a directional role; and then the egg membrane fusion of sperm acrosome membrane area. Many animal sperm into the egg cytoplasm after rotating 180 degrees, the middle and the head of the sperm to rotate together, so that Centriole
Toward the center of egg. Then the male pronucleus formed gradually, at the same time the particle center around a star, together with the male pronucleus transfer to the female star with prokaryotic. The sperm midpiece and tail soon degraded and absorbed. The egg nucleus after the completion of the two meiosis, the formation of female Prokaryotic
. Two female and male pronucleus meet, or fusion, two Nuclear membrane
Into a; or in combination, the two nuclear compound, the nuclear membrane disappeared, only Chromosome set
Together, in order to establish zygotic genome, thus completing fertilization.
Fertilization Biochemical changes
The eggs before the metabolic level is very low, the synthetic activities of DNA, RNA and protein synthesis are very few. So from the eggs, if not fertilized, soon died.
When the surface of sperm and eggs, eggs rapidly increasing rate of metabolism, and the synthesis of DNA. Details of the egg activation mechanism is not clear, only know how to open the sperm only played the role of switching procedures. In addition to sperm, some other non-specific chemical or physical treatment, also can make the egg activation, such as acupuncture frogspawn, also make the excitement. The initial excitement without any new protein synthesis.
In the early stages of the sea urchin egg activation, increased membrane permeability to sodium ions, sodium ion influx, resulting in membrane depolarization in seconds; calcium ions from the cell in stock release, the 20 ~ 30 seconds eggs free calcium increased up to 100 times; with the sodium ion influx hydrogen ion efflux, resulting in a minute egg pH value increased significantly. These ions changes, evoked cortical response, leading to block excess sperm into the egg, egg and stir up the further development. The increase of intracellular free calcium ion, arrived in egg activation of calmodulin, which further activate other proteins in the eggs. Then increased protein synthesis, DNA also began to copy.
In the sea urchin eggs, calcium may also be passed Calmodulin
The activation of certain specific transporter protein, egg plasma membrane, hydrogen ions to the output cell. The pH value increased in the eggs, will lead to increased protein synthesis and replication of DNA. The outflow of sodium ions flow depends on the hydrogen ion. The new synthesis of these proteins is not dependent on RNA, but stored in eggs of mRNA to cover and ribosome activation results.
Study on the mechanism of fertilization, is one of the basic guarantee for the effective control and sexual reproduction of animal breeding and breeding. The birth of human "test tube baby" only a few success stories. Because of the many problems still exist in suspense fertilization and further normal growth mechanism, many animal In vitro fertilization
The attempt failed. These failures show that The basic theory research
Fertilization Artificial insemination conditions
Artificial insemination is the most basic conditions of the at least one side of the fallopian tube is completely unobstructed, the woman has a spontaneous ovulation or after ovulation treatment can ovulation; the male sperm must have a certain number of live sperm. Generally speaking, to do artificial insemination pregnancy, both of which are indispensable.