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Fertilized Egg
A zygote (; , ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. The sexual fusion of haploid cells is called karyogamy, the result of which is the formation of a diploid cell called the zygote or zygospore. History German zoologists Oscar and Richard Hertwig made some of the first discoveries on animal zygote formation in the late 19th century. In multicellular organisms The zygote is the earliest developmental stage. In humans and most other anisogamous organisms, a zygote is formed when an egg cell and sperm cell come together to create a new unique organism. The formation of a totipotent zygote with the potential to produce a whole organism depends on epigenetic reprogramming. DNA demethylation of the paternal genome in the zygote appears to be an important part of epigenetic reprogramming. In th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egg Cell
The egg cell or ovum (: ova) is the female Reproduction, reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete is not capable of movement (non-motile). If the male gamete (sperm) is capable of movement, the type of sexual reproduction is also classified as oogamous. A nonmotile female gamete formed in the oogonium of some algae, fungi, oomycetes, or bryophytes is an oosphere. When fertilized, the oosphere becomes the oospore. When egg and sperm fuse together during fertilisation, a diploid cell (the zygote) is formed, which rapidly grows into a new organism. History While the non-mammalian animal egg was obvious, the doctrine ''ex ovo omne vivum'' ("every living [animal comes from] an egg"), associated with William Harvey (1578–1657), was a rejection of spontaneous generation and preformationism as well as a bold assumption that mammals als ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Demethylation
For molecular biology in mammals, DNA demethylation causes replacement of 5-methylcytosine (5mC) in a DNA sequence by cytosine (C) (see figure of 5mC and C). DNA demethylation can occur by an active process at the site of a 5mC in a DNA sequence or, in replicating cells, by preventing addition of methyl groups to DNA so that the replicated DNA will largely have cytosine in the DNA sequence (5mC will be diluted out). Methylated cytosine is frequently present in the linear DNA sequence where a cytosine is followed by a guanine in a Directionality (molecular biology), 5' → 3' direction (a CpG site). In mammals, DNA methyltransferases (which add methyl groups to DNA bases) exhibit a strong sequence preference for cytosines at CpG sites. There appear to be more than 20 million CpG dinucleotides in the human genome (see CpG site#Genomic distribution, genomic distribution). In mammals, on average, 70% to 80% of CpG cytosines are methylated, though the level of methylation varies with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fallopian Tube
The fallopian tubes, also known as uterine tubes, oviducts or salpinges (: salpinx), are paired tubular sex organs in the human female body that stretch from the Ovary, ovaries to the uterus. The fallopian tubes are part of the female reproductive system. In other vertebrates, they are only called oviducts. Each tube is a muscular hollow organ that is on average between in length, with an external diameter of . It has four described parts: the intramural part, isthmus, ampulla, and infundibulum with associated fimbriae. Each tube has two openings: a proximal opening nearest to the uterus, and a distal opening nearest to the ovary. The fallopian tubes are held in place by the mesosalpinx, a part of the broad ligament mesentery that wraps around the tubes. Another part of the broad ligament, the mesovarium suspends the ovaries in place. An ovum, egg cell is transported from an ovary to a fallopian tube where it may be human fertilization, fertilized in the ampulla of the tube. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conceptus
A conceptus (from Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...: ''concipere'', to conceive) is an embryo and its appendages (adnexa), the associated membranes, placenta, and umbilical cord; the products of conception or, more broadly, "the product of conception at any point between fertilization and birth."'' The American Heritage Dictionary of the English Language'' (2011), 5th ed., p. 381. The conceptus includes all structures that develop from the zygote, both embryonic and extraembryonic. It includes the embryo as well as the embryonic part of the placenta and its associated membranes: amnion, chorion ( gestational sac), and yolk sac. References Embryology Human pregnancy {{Developmental-biology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryo
An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm cell. The resulting fusion of these two cells produces a single-celled zygote that undergoes many cell divisions that produce cells known as blastomeres. The blastomeres (4-cell stage) are arranged as a solid ball that when reaching a certain size, called a morula, (16-cell stage) takes in fluid to create a cavity called a blastocoel. The structure is then termed a blastula, or a blastocyst in mammals. The mammalian blastocyst hatches before implantating into the endometrial lining of the womb. Once implanted the embryo will continue its development through the next stages of gastrulation, neurulation, and organogenesis. Gastrulation is the formation of the three germ layers that will form all of the different parts of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Implantation (human Embryo)
Implantation, also known as nidation, is the stage in the mammalian embryonic development in which the blastocyst hatches, attaches, adheres, and penetrates into the endometrium of the female's uterus. Implantation is the first stage of gestation, and, when successful, the female is considered to be pregnant. An implanted embryo is detected by the presence of increased levels of human chorionic gonadotropin (hCG) in a pregnancy test. The implanted embryo will receive oxygen and nutrients in order to grow. For implantation to take place the uterus must become receptive. Uterine receptivity involves much cross-talk between the embryo and the uterus, initiating changes to the endometrium. This stage gives a synchrony that opens a window of implantation that enables successful implantation of a viable embryo. The endocannabinoid system plays a vital role in this synchrony in the uterus, influencing uterine receptivity, and embryo implantation. The embryo expresses cannabinoi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blastomere
In biology, a blastomere is a type of cell produced by cell division (cleavage) of the zygote after fertilization; blastomeres are an essential part of blastula formation, and blastocyst formation in mammals. Human blastomere characteristics In humans, blastomere formation begins immediately following fertilization and continues through the first week of embryonic development. About 90 minutes after fertilization, the zygote divides into two cells. The two-cell blastomere state, present after the zygote first divides, is considered the earliest mitotic product of the fertilized oocyte. These mitosis, mitotic divisions continue and result in a grouping of cells called blastomeres. During this process, the total size of the embryo does not increase, so each division results in smaller and smaller cells. When the zygote contains 16 to 32 blastomeres it is referred to as a morula. These are the preliminary stages in the embryo beginning to form. Once this begins, microtubules wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pronucleus
A pronucleus (: pronuclei) denotes the nucleus found in either a sperm or egg cell during the process of fertilization. The sperm cell undergoes a transformation into a pronucleus after entering the egg cell but prior to the fusion of the genetic material of both the sperm and egg. In contrast, the egg cell possesses a pronucleus once it becomes haploid, not upon the arrival of the sperm cell. Haploid cells, such as sperm and egg cells in humans, carry half the number of chromosomes present in somatic cells, with 23 chromosomes compared to the 46 found in somatic cells. It is noteworthy that the male and female pronuclei do not physically merge, although their genetic material does. Instead, their membranes dissolve, eliminating any barriers between the male and female chromosomes, facilitating the combination of their chromosomes into a single diploid nucleus in the resulting embryo, which contains a complete set of 46 chromosomes. The presence of two pronuclei serves as the in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meiosis
Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one copy of each chromosome (haploid). Additionally, prior to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome. Later on, during fertilisation, the haploid cells produced by meiosis from a male and a female will fuse to create a zygote, a cell with two copies of each chromosome. Errors in meiosis resulting in aneuploidy (an abnormal number of chromosomes) are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells, each with half the number of chromosomes as the original parent cell. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diploid Cell
Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, respectively, in each homologous chromosome pair—the form in which chromosomes naturally exist. Somatic cells, tissues, and individual organisms can be described according to the number of sets of chromosomes present (the "ploidy level"): monoploid (1 set), diploid (2 sets), triploid (3 sets), tetraploid (4 sets), pentaploid (5 sets), hexaploid (6 sets), heptaploid or septaploid (7 sets), etc. The generic term polyploid is often used to describe cells with three or more sets of chromosomes. Virtually all sexually reproducing organisms are made up of somatic cells that are diploid or greater, but ploidy level may vary widely between different organisms, between different tissues within the same organism, and at different stages in an org ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Male
Male (Planet symbols, symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or Egg cell, ovum, in the process of fertilisation. A male organism cannot sexual reproduction, reproduce sexually without access to at least one ovum from a female, but some organisms can reproduce both sexually and Asexual reproduction, asexually. Most male mammals, including male humans, have a Y chromosome, which codes for the production of larger amounts of testosterone to develop male reproductive organs. In humans, the word ''male'' can also be used to refer to gender, in the social sense of gender role or gender identity. Overview The existence of separate sexes has evolved independently at different times and in different lineage (evolution), lineages, an example of convergent evolution. The repeated pattern is sexual reproduction in isogamy, isogamous species with two or more mating types with gametes of identic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oocyte
An oocyte (, oöcyte, or ovocyte) is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell (PGC), which then undergoes mitosis, forming oogonia. During oogenesis, the oogonia become primary oocytes. An oocyte is a form of genetic material that can be collected for cryoconservation. Formation The formation of an oocyte is called oocytogenesis, which is a part of oogenesis. Oogenesis results in the formation of both primary oocytes during fetal period, and of secondary oocytes after it as part of ovulation. Characteristics Cytoplasm Oocytes are rich in cytoplasm, which contains yolk granules to nourish the cell early in development. Nucleus During the primary oocyte stage of oogenesis, the nucleus is called a germinal vesicle. The only normal human type of secondary oocyte has the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
