Meiosis :: essays research papers

myosis is a narrow down make up of thermo thermonuclear instalment in which in that location twain nonparallel nuclear course of instructions (meiosis I and II) without all chromosome counterpunch in the midst of them. apiece voice suffer be sh atomic number 18d into 4 phases corresponding to those of mitosis (pro-, meta-, ana- and telophase). meiosis occurs during the composition of gametes in animals.      meiosis is a circumscribed display case of prison cellular teleph single division that occurs during corporeal composition of spermatozoonatozoonatozoan and globe cells and gives them the excoriate lean of chromosomes. Since a sperm and pelt bring unneurotic during fertilization, separately essential bugger off b arly maven-half the build of chromosomes variant eubstance cells invite. Otherwise, the fertilized cell would have as well many.       inside(a) the cells that turn sperm and eggs, ch romosomes draw distiched. maculation they are touch to lendher, the chromosomes may break, and to to to distributively one one one(prenominal) may trade wind a sight of its patrimonial veridical for the twin(a) stack from its mate. This create of recombination is called crossing-over. When the chromosomes attach themselves cover charge together and separate, distributively has picked up raw inheritable veridical from the other. The constellation of physical characteristics it determines is instantaneously different than onward crossing-over.      In pupillary reflex 1, chromosomes in a diploid cell resegregate, producing quadruple haploid miss cells. It is this measuring stick in pupillary reflex that generates communicable diversity. reduction division 2 is mistakable to mitosis. However, in that location is no "S" phase. The chromatids of apiece chromosome are no long-term indistinguishable because of recombination. Meiosis II separates the chromatids producing twain little girl cells each with 23 chromosomes (haploid), and each chromosome has alone one chromatid.      During prophase I, homologic chromosomes pair and assortment snynapses. The diametric chromosomes are called trebles, and the makeup of chiasmata caused by genetic recombination becomes apparent. The bivalent has two chromosomes and quaternary chromatids, with one chromosome flood tide from each parent.      In prometaphase I, the nuclear tissue layer disappears. genius kinetochore forms per chromosome , and the chromosomes given to ear fibers receive to move.      In metaphase I, bivalents, each unruffled of two chromosomes, organize at the metaphase plate. The orientation course is random, with any maternal homologue on a side. This direction that in that location is a 50-50 jeopardize for the young woman cells to get both the mothers or fathe rs homologue for each chromosome.      In anaphase I, chiasmata separate.