At what point is meiosis II completed within the egg?
After ovulation the oocyte is arrested in metaphase of meiosis II until fertilization. At fertilization, the secondary oocyte completes meiosis II to form a mature oocyte (23,1N) and a second polar body.
Does sperm complete meiosis II prior to fertilization?
The secondary oocyte remains paused in meiosis II until a sperm cell fertilizes it. This triggers the egg to complete meiosis II. During meiosis II, the duplicated chromosomes are separated into a polar body and a mature ovum. At this point, the haploid nuclei of the egg and sperm are able to fuse to form the zygote.
What is the trigger that leads the oocyte to complete meiosis 2 and becoming an egg?
increased maturation promoting factor (MPF)The ovulated oocyte is maintained at metaphase II nuclear status by increased maturation promoting factor (MPF) activity (A). Fertilization triggers continuation of meiosis II, resulting in a two-pronuclear pre-embryo displaying two polar bodies and pronucleus (B).
At what point is meiosis II completed for the female gamete?
The answer is c) fertilization. The female gamete stays locked in metaphase II until fertilized by the male gamete.
Does meiosis 2 happen after fertilization?
Meiosis II is completed only if fertilization occurs, resulting in a fertilized mature ovum and the second polar body. So in short, the egg is stuck in metaphase II until fertilization.
Does meiosis happen before fertilization?
1 Answer. Meiosis occurs before fertilization.
What triggers the completion of meiosis II?
Fertilization and completion of meiosis. (A) Fertilization induces the transition from metaphase II to anaphase II, leading to completion of oocyte meiosis and emission of a second polar body (which usually degenerates).
What stimulates the secondary oocyte to complete meiosis II?
The secondary oocyte completes meiosis II only when fertilized by a spermatozoan. After fertilization is initiated, the secondary oocyte begins its second meiotic division, resulting in the formation of a mature ovum and another polar body. At this point, the ovum is ready to fuse with the spermatozoan.
What must happen before the second meiosis continues?
E. The chromosomes must be duplicated. Before mitosis can begin, the chromosomes, or genetic material, must be copied, which occurs during interphase.
Where does meiosis 2 occur during oogenesis?
secondary oocytesMeiosis II occurs in the secondary oocytes. Meiosis II is arrested at the metaphase II stage and is only completed after the penetration of sperm into the ovum.
Why does oogenesis occur before birth?
Oogenesis begins before birth but is not finished until after puberty. A mature egg forms only if a secondary oocyte is fertilized by a sperm. Oogenesis begins long before birth when an oogonium with the diploid number of chromosomes undergoes mitosis. It produces a diploid daughter cell called a primary oocyte.
What stage of meiosis is an ovulated egg in?
second meiotic metaphaseThe ovulated egg is in second meiotic metaphase when it is released (Figure 19.24).