Freeresponse Meiosis Essay

553 Words3 Pages
Free Response: Meiosis Meiosis is known as the division of sex cells (gametes). Meiosis occurs in organisms that reproduce sexually. Meiosis is a type of cell division in which the chromosomes are not completely reproduced. Instead of full cell division, the chromosome number is halved so that these cells can be used in sexual reproduction. The joining of two sex cells will produce a cell with the full number of chromosomes. That cell will then continue to divide in order to create a new organism. Meiosis is divided up into several stages, Meiosis I and Meiosis II. They are very to regular mitosis, but four cells are produced instead of the two by normal cell division. In Meiosis I, the homologous pairs in a diploid cell separate to produce two haploid cells. Haploid cells are cells with a single set of chromosomes. The next phase, prophase I, includes the homologous chromosomes pair and the crossing over. Crossing over is a process where two chromosomes pair up and switch sections of their DNA. Matching regions on matching chromosomes break and then reconnect to the other chromosomes, which allows for variations in genes. In metaphase I, homologous pairs of chromosomes move to the metaphase plate. Microtubules appear from the centrioles and attach the homologous pairs which then line up in the middle of the cell. Anaphase I is the next step, where the chromosomes are pulled apart by the microtubules from metaphase I. This forms two haploid sets of chromosomes. The last step before the complete separation of the cell is Telophase I. In this phase, the chromosomes reach the poles. The nuclear membrane forms around the two sets of chromosomes and cytokinesis occurs. Meiosis II now starts. The two haploid cells begin to divide again. In prophase II, the nucleoli and nuclear envelope start to disappear. Metaphase II is the same as Metaphase I, where the chromosomes

More about Freeresponse Meiosis Essay

Open Document