The dictyate or dictyotene
is a prolonged resting phase in
oogenesis
Oogenesis () or ovogenesis 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 before birth during embryonic devel ...
. It occurs in the stage of
meiotic prophase I in
ootidogenesis
Oogenesis () or ovogenesis 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 before birth during embryonic devel ...
. It starts late in fetal life
[ and is terminated shortly before ]ovulation
Ovulation is an important part of the menstrual cycle in female vertebrates where the egg cells are released from the ovaries as part of the ovarian cycle. In female humans ovulation typically occurs near the midpoint in the menstrual cycle and ...
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
Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a female, the testicles i ...
commences and the cells complete ootidogenesis
Oogenesis () or ovogenesis 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 before birth during embryonic devel ...
.
In both mouse and human, oocyte DNA of older individuals has substantially more double-strand breaks than that of younger individuals.homologous recombination
Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in Cell (biology), cellular organi ...
al repair.[ DNA repair capability appears to be a key quality control mechanism in the female germ line and a critical determinant of ]fertility
Fertility in colloquial terms refers the ability to have offspring. In demographic contexts, fertility refers to the actual production of offspring, rather than the physical capability to reproduce, which is termed fecundity. The fertility rate ...
.[
]
Translation halt
There are a lot of mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein.
mRNA is ...
s that have been transcribed but not translated during dictyate.
Biochemistry mechanism
Translation of mRNA in dictyate is partly explained by molecules binding to sites on the mRNA strain, which results in that initiation factor
In molecular biology, initiation factors are proteins that bind to the small subunit of the ribosome during the initiation of Translation (genetics), translation, a part of protein biosynthesis.
Initiation factors can interact with repressors to ...
s of translation can not bind to that site. Two such molecules, that impedes initiation factors, are CPEB and ''maskin'', which bind to CPE (cytoplasmic polyadenylation element). When these two molecules remain together, then maskin binds the initiation factor eIF-4E,[ and thus eIF4E can no longer interact with the other initiation factors][{{cite book , vauthors=Lodish HF, Berk A, Kaiser C, Krieger M, Scott MP, Bretscher A, Ploegh HL, Matsudaira PT , title=Molecular cell biology , publisher=W.H. Freeman , edition=6th , date=2008 , isbn=978-0-7167-4366-8 , pages=351 , oclc=83758878] and no translation occurs. On the other hand, dissolution of the CPEB/maskin complex leads to eIF-4E binding to the initiation factor eIF-4G
Eukaryotic initiation factors (eIFs) are Protein, proteins or Protein complex, protein complexes involved in the initiation phase of eukaryotic translation. These proteins help stabilize the formation of ribosomal preinitiation complexes around the ...
,[ and thus translation starts, which contributes to the end of dictyate and further maturation of the oocyte.
]
See also
*Oogenesis
Oogenesis () or ovogenesis 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 before birth during embryonic devel ...
* Immature ovum
*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 sp ...
*Zygote
A zygote (; , ) is a eukaryote, eukaryotic cell (biology), 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 individ ...
References
Developmental biology