Search results
Results From The WOW.Com Content Network
Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism , gametogenesis occurs by meiotic division of diploid gametocytes into various gametes, or by mitosis.
The coalescence of the neural folds occurs first in the region of the hind brain, and from there extends forward and backward; toward the end of the third week, the front opening (anterior neuropore) of the tube finally closes at the anterior end of the future brain, and forms a recess that is in contact, for a time, with the overlying ectoderm ...
Gametogenesis is the formation or production of gametes (taking place during meiosis). The development and maturation of sex cells also takes place during meiosis. Gametogenesis is also the process of formation in male and female gametes that occur in the gonads (ovary and testis). Both male and female produce gametes.
Primordial germ cells are among the first lineages that are established in development [1] and they are the precursors for gametes. [2] It is thought that the process of primordial germ cell migration itself has been conserved rather than the specific mechanisms within it, as chemoattraction and repulsion seem to have been borrowed from blood cells, neurones, and the mesoderm. [1]
These processes are outlined in the article gametogenesis. During gametogenesis in mammals many genes encoding proteins that take part in DNA repair mechanisms show enhanced or specialized expression [ 13 ] These mechanisms include meiotic homologous recombinational repair and mismatch repair .
Thus, spermatogenesis is the male version of gametogenesis, of which the female equivalent is oogenesis. In mammals it occurs in the seminiferous tubules of the male testes in a stepwise fashion. Spermatogenesis is highly dependent upon optimal conditions for the process to occur correctly, and is essential for sexual reproduction.
The first “test tube baby” was born in England in 1978, and since tracking officially began in 1985, more than 1.2 million babies have been born in the U.S. with the aid of assisted ...
The mutation frequencies for cells in different stages of gametogenesis are about 5 to 10-fold lower than in somatic cells both for spermatogenesis [18] and oogenesis. [19] The lower frequencies of mutation in germline cells compared to somatic cells appears to be due to more efficient DNA repair of DNA damages, particularly homologous ...