The genetic differences ensure siblings of the same parents are never entirely genetically identical. ![]() These haploid cells become unfertilized eggs in females and sperm in males. In humans, meiosis produces genetically different haploid daughter cells, each with 23 chromosomes that consist of one chromatid. Note that these four cells are not identical, as random arrangements of bivalents and crossing over in meiosis I leads to different genetic composition of these cells. Division of the cytoplasm during cytokinesis results in four haploid cells. In anaphase II, chromosomes divide at the centromeres (like in mitosis) and the resulting chromosomes, each with one chromatid, move toward opposite poles of the cell.įour haploid nuclei (containing chromosomes with single chromatids) are formed in telophase II. The chromosomes align on the metaphase plate during metaphase II in preparation for centromeres to divide in the next phase. Spindle fibers reform and attach to centromeres in prophase II. In humans (2 n = 46), who have 23 pairs of chromosomes, the number of chromosomes remains unchanged from the beginning till the end of meiosis II ( n = 23). In addition, there are no opportunities for. Notice that these four meiocytes are genetically different from one another. DNA replication does not occur during prophase II each chromosome still consists of the two sister chromatids. ![]() As shown in the figure below, meiosis II begins with two haploid ( n = 2) cells and ends with four haploid ( n = 2) cells. The paired and replicated chromosomes are called bivalents (two chromosomes) or tetrads (four chromatids), with one chromosome coming from each parent. In meiosis II, the phases are, again, analogous to mitosis: prophase II, metaphase II, anaphase II, and telophase II (see figure below). Chromosomal numbers, which have already been reduced to haploid ( n) by the end of meiosis I, remain unchanged after this division. The second part of the meiosis, meiosis II, resembles mitosis more than meiosis I. ![]() Chromosomal replication does not occur between meiosis I and meiosis II meiosis I proceeds directly to meiosis II without going through interphase.
0 Comments
Leave a Reply. |