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Dictyate
The dictyate or dictyoteneMedical Physiology, Boron & Boulpaep, , Elsevier Saunders 2005. Updated edition. 1300 pages. is a prolonged resting phase in oogenesis. It occurs in the stage of meiotic prophase I in ootidogenesis. It starts late in fetal life and is terminated shortly before ovulation by the LH surge. Thus, although the majority of oocytes are produced in female fetuses before birth, these pre-eggs remain arrested in the dictyate stage until puberty commences and the cells complete ootidogenesis. In both mouse and human, oocyte DNA of older individuals has substantially more double-strand breaks than that of younger individuals.{{cite journal , vauthors=Titus S, Li F, Stobezki R, Akula K, Unsal E, Jeong K, Dickler M, Robson M, Moy F, Goswami S, Oktay K , title=Impairment of BRCA1-related DNA double-strand break repair leads to ovarian aging in mice and humans , journal=Sci Transl Med , volume=5 , issue=172 , pages=172ra21 , year=2013 , pmid=23408054 , doi=10.1126/scitrans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oogenesis
Oogenesis, ovogenesis, or oögenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated in the embryonic stage. Oogenesis in non-human mammals In mammals, the first part of oogenesis starts in the germinal epithelium, which gives rise to the development of ovarian follicles, the functional unit of the ovary. Oogenesis consists of several sub-processes: oocytogenesis, ootidogenesis, and finally maturation to form an ovum (oogenesis proper). Folliculogenesis is a separate sub-process that accompanies and supports all three oogenetic sub-processes. Oogonium —(Oocytogenesis)—> Primary Oocyte —(Meiosis I)—> First Polar body (Discarded afterward) + Secondary oocyte —(Meiosis II)—> Second Polar Body (Discarded afterward) + Ovum Oocyte meiosis, important to all animal life cycles yet unlike all other instances of animal cell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ootidogenesis
Oogenesis, ovogenesis, or oögenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated in the embryonic stage. Oogenesis in non-human mammals In mammals, the first part of oogenesis starts in the germinal epithelium (female), germinal epithelium, which gives rise to the development of ovarian follicles, the functional unit of the ovary. Oogenesis consists of several sub-processes: oocytogenesis, ootidogenesis, and finally maturation to form an ovum (oogenesis proper). Folliculogenesis is a separate sub-process that accompanies and supports all three oogenetic sub-processes. Oogonium —(Oocytogenesis)—> Primary Oocyte —(Meiosis I)—> First Polar body (Discarded afterward) + Secondary oocyte —(Meiosis II)—> Second Polar Body (Discarded afterward) + Ovum Oocyte meiosis, important to all animal life cycles yet unlike all o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Immature Ovum
An immature ovum is a cell that goes through the process of oogenesis to become an ovum. It can be an oogonium, an oocyte, or an ootid. An oocyte, in turn, can be either primary or secondary, depending on how far it has come in its process of meiosis. Oogonium Oogonia are the cells that turn into primary oocytes in oogenesis. They are diploid, i.e. Oogonia are created in early embryonic life. All have turned into primary oocytes at late fetal age. Primary oocyte The primary oocyte is defined by its process of ootidogenesis, which is meiosis. It has duplicated its DNA, so that each chromosome has two chromatids, i.e. 92 chromatids all in all (4C). When meiosis I is completed, one secondary oocyte and one polar body is created. Primary oocytes have been created in late fetal life. This is the stage where immature ova spend most of their lifetime, more specifically in diplotene of prophase I of meiosis. The halt is called dictyate. Most degenerate by atresia, but a few go t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oocytes
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 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oogenesis
Oogenesis, ovogenesis, or oögenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated in the embryonic stage. Oogenesis in non-human mammals In mammals, the first part of oogenesis starts in the germinal epithelium, which gives rise to the development of ovarian follicles, the functional unit of the ovary. Oogenesis consists of several sub-processes: oocytogenesis, ootidogenesis, and finally maturation to form an ovum (oogenesis proper). Folliculogenesis is a separate sub-process that accompanies and supports all three oogenetic sub-processes. Oogonium —(Oocytogenesis)—> Primary Oocyte —(Meiosis I)—> First Polar body (Discarded afterward) + Secondary oocyte —(Meiosis II)—> Second Polar Body (Discarded afterward) + Ovum Oocyte meiosis, important to all animal life cycles yet unlike all other instances of animal cell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initiation Factor
Initiation factors are proteins that bind to the small subunit of the ribosome during the initiation of translation, a part of protein biosynthesis. Initiation factors can interact with repressors to slow down or prevent translation. They have the ability to interact with activators to help them start or increase the rate of translation. In bacteria, they are simply called IFs (i.e.., IF1, IF2, & IF3) and in eukaryotes they are known as eIFs (i.e.., eIF1, eIF2, eIF3). Translation initiation is sometimes described as three step process by which initiation factors help to carry out. First, the tRNA carrying a methionine amino acid binds to the small ribosome, then binds to the mRNA, and finally joining together with the large ribosome. The initiation factors that help with this process each have different roles and structures. Types The initiation factors are divided into three major groups by taxonomic domains. There are some homologies shared (click the domain names to see the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryo
An embryo is an initial stage of development of 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 are arranged as a solid ball that when reaching a certain size, called a morula, 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 the body. Neurulation forms the nervous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF-4G
Eukaryotic initiation factors (eIFs) are proteins or protein complexes involved in the initiation phase of eukaryotic translation. These proteins help stabilize the formation of ribosomal preinitiation complexes around the start codon and are an important input for post-transcription gene regulation. Several initiation factors form a complex with the small 40S ribosomal subunit and Met-tRNAiMet called the 43S preinitiation complex (43S PIC). Additional factors of the eIF4F complex (eIF4A, E, and G) recruit the 43S PIC to the five-prime cap structure of the mRNA, from which the 43S particle scans 5'-->3' along the mRNA to reach an AUG start codon. Recognition of the start codon by the Met-tRNAiMet promotes gated phosphate and eIF1 release to form the 48S preinitiation complex (48S PIC), followed by large 60S ribosomal subunit recruitment to form the 80S ribosome. There exist many more eukaryotic initiation factors than prokaryotic initiation factors, reflecting the greater biol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF-4E
Eukaryotic initiation factors (eIFs) are proteins or protein complexes involved in the initiation phase of eukaryotic translation. These proteins help stabilize the formation of ribosomal preinitiation complexes around the start codon and are an important input for post-transcription gene regulation. Several initiation factors form a complex with the small 40S ribosomal subunit and Met-tRNAiMet called the 43S preinitiation complex (43S PIC). Additional factors of the eIF4F complex (eIF4A, E, and G) recruit the 43S PIC to the five-prime cap structure of the mRNA, from which the 43S particle scans 5'-->3' along the mRNA to reach an AUG start codon. Recognition of the start codon by the Met-tRNAiMet promotes gated phosphate and eIF1 release to form the 48S preinitiation complex (48S PIC), followed by large 60S ribosomal subunit recruitment to form the 80S ribosome. There exist many more eukaryotic initiation factors than prokaryotic initiation factors, reflecting the greater biol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytoplasmic Polyadenylation Element
The cytoplasmic polyadenylation element (CPE) is a sequence element found in the 3' untranslated region of messenger RNA. While several sequence elements are known to regulate cytoplasmic polyadenylation, CPE is the best characterized. The most common CPE sequence is UUUUAU, though there are other variations. Binding of CPE binding proteinCPEB to this region promotes the extension of the existing polyadenine tail and, in general, activation of the mRNA for protein translation. This elongation occurs after the mRNA has been exported from the nucleus to the cytoplasm. A longer poly(A) tail attracts more cytoplasmic polyadenine binding proteins (PABPs) which interact with several other cytoplasmic proteins that encourage the mRNA and the ribosome to associate. The lengthening of the poly(A) tail thus has a role in increasing translational efficiency of the mRNA. The polyadenine tails are extended from approximately 40 bases to 150 bases. Cytoplasmic polyadenylation should be distin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CPEB
CPEB, or cytoplasmic polyadenylation element binding protein, is a highly conserved RNA-binding protein that promotes the elongation of the polyadenine tail of messenger RNA. CPEB most commonly activates the target RNA for translation, but can also act as a repressor, dependent on its phosphorylation state. In animals, CPEB is expressed in several alternative splicing isoforms that are specific to particular tissues and functions, including the self-cleaving Mammalian CPEB3 ribozyme. CPEB was first identified in ''Xenopus'' oocytes and associated with meiosis; a role has also been identified in the spermatogenesis of '' Caenorhabditis elegans''. CPEB is involved in closed-loop regulation of mRNAs that keeps them inactive. The closed-loop structure between the 3'UTR and 5'UTR inhibits translation. This has been observed in ''Xenopus laevis'' in which eIF4E bound to the 5' cap interacts with Maskin bound to CPEB on the 3' UTR creating translationally inactive transcripts. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Transcription
Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called non-coding RNAs (ncRNAs). mRNA comprises only 1–3% of total RNA samples. Less than 2% of the human genome can be transcribed into mRNA ( Human genome#Coding vs. noncoding DNA), while at least 80% of mammalian genomic DNA can be actively transcribed (in one or more types of cells), with the majority of this 80% considered to be ncRNA. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. Transcription proceeds in the following general steps: # RNA polymerase, together with one or more general transcription factors, binds to promoter DNA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
