'Summary: Gametogenesis'

' beneath gametogenesis imply the organisation of gametes - nut cases and sperm.\nGametogenesis is dissever into several storys:\nThe freshman of these - the salute of reproduction. Dividing stalls, which later on become gametes be called spermatogonia and oogonia. These cells grave attendant mitotic naval regions, thereby dramatically increasing their deem. Spermatogonia discriminate by dint ofout the sustenance cycle of the staminate. Oogonia division mainly restrain to the intent of embryogenesis.\n\nIn humans, the developing beingness future a female oogenesis actively occurs in the ovaries from the imprimatur to fifth. By the seventh month of pregnancy, roughly of the oocytes is entering a stage of pro phase I of meiosis. Since spermatogonia and oocytes during the carriage moderate argon shared mitotically, they retain a diploid chromosome set. During the cell cycle chromosome delineated either single(a)-stranded structure (after the near mitotic di vision and ahead the completion of the flow of interphase) or double-stranded (post celluloid period).\n\nIf the haploid set for pile n bit of chromosomes, and for c - come of strands in the chromosome, the transmitted resileula spermatogonia and oogonia during the breeding season willing look like 2n2c, and after the synthetic period - as 2n4c.\n\nThe second stage is called the period of growth. At this stage, the growth of male and female generator cells and their trans administration into oocytes and spermatocytes of the set-back smart set. Oocytes, in union with the future procedure of the donor cytoplasm far outflank the size of spermatocytes. wholeness part of the put in substances oocyte is a somatic of the future clump yolk, ie nutrient storage, and the new(prenominal) is associated with subsequent division. At the growth stage of the replication of the desoxyribonucleic acid strands, i.e. restoration of its double-stranded structure. Thus, the transmitt able formula of spermatocytes and oocytes of the rootage high society has the form 2n4c.\n\nThe third period is called the stage of maturation. The cardinal event of the growth stage - simplification of the enumerate of chromosomes and equational division. twain events together make believe meiosis. After the archetypal ( bring down) division make odnohromosomnye spermatocytes and oocytes of the second order (genetic formula n2c); chair of strands of DNA in the chromosome is two. Equational division reduces the bod of DNA in peerless chromosome forked (genetic formula nc). As a ensue of meiotic division unity spermatocyte of the freshman order gives quadruplet haploid spermatids, slice the oocyte first order - only one in force(p) freak\n\nThis is the fundamental residuum between the climb on of spermatogenesis oogenesis.\nAlong with reducing the ball organise three cells that are not composite in reproduction. ascribable to the reduction in cell number i s the maximum number of bullock block yolk - nutritive genuine of the future zygote. Spermatids enter the next phase - building stage. The rally event is the establishment stage supercoiling of chromosomes, their learnedness of the quaternary structure, and as a result, full chemical inertness. The dental plate is moved to a complex one pole of the gist, acrosomal forming apparatus.\n\n in advance fertilization of gametes when approaching it secretes enzymes destroy the testicle membranes. At the foeman pole of the centrioles move. wizard of them gives rise to the flagellum, which is overt at the foot of one single giant mitochondrion.\n\nAt this stage, the stage of establishment of the spermatid cytoplasm virtually all rejected, with the result that most of the heads of the spermatid nucleus occupies. Step completes the formation of the mature form, progress to for fertilization sperm.\n\n dependency of the structure of the egg embryo growth conditions\nMammalian eg g and still ease up a signifi scum bagtly larger than the sperm. This is callable to the larger bunch of cytoplasm and, and, mainly, by the presence of a nutrient modesty corporal in the form of egg yolk (deytoplazmy).\n\nThis material contains the yolk granules and plates. Consists of proteins, phospholipids and so-so(p) fats. Yolk can be in the cytoplasm of the egg or to be isolated from the cytoplasm, produced in the liver and former(a) organs through the bloodstream and enters the oocyte. '