Answer: In humans, meiosis is the process by which sperm cells and egg cells are produced. In the male, meiosis takes place after puberty. Diploid cells within the testes undergo meiosis to produce haploid sperm cells with 23 chromosomes. A single diploid cell yields four haploid sperm cells through meiosis. In females, meiosis begins during the fetal stage when a series of diploid cells enter meiosis I. At the conclusion of meiosis I, the process comes to a halt, and the cells gather in the ovaries. At puberty, meiosis resumes. One cell at the end of meiosis I enters meiosis II each month. The result of meiosis II is a single egg cell per cycle (the other meiotic cells disintegrate). Each egg cell contains 23 chromosomes and is haploid. The union of the egg cell and the sperm cell leads to the formation of a fertilized egg cell with 46 chromosomes, or 23 pairs. Fertilization restores the diploid number of chromosomes. The fertilized egg cell, a diploid, is a zygote. Further divisions of the zygote by mitosis eventually yield a complete human being.
In meiosis-II the separation of two chromatids occur so that equal number of chromatids (in fact chromosome due to duplication of genetic material) goes to each of the daughter cell. Thus, at the end of meiosis-II, four daughter cells are formed. Each cell has half the number of chromosomes present in the diploid cell.Feb
The expected growth mark marker for a 6 month old infant is that the infant can transfer objects from hand to hand, rolls from prone to supine, sits well unsupported, presents with stranger anxiety, and that the patient can babble.
