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(一)减数分裂与细胞学、遗传学的关系现行《生物》课本中“减数分裂与生殖细胞的成熟”一节教材是全书中重要的一节,减数分裂是一种特殊的有丝分裂。在减数分裂过程中细胞经过连续两次分裂,而染色体只复制一次,结果使性细胞中染色体数目减半。性细胞再经受精作用形成合子,合子中染色体数目又恢复到亲代体细胞中染色体数目,从而使亲子代细胞中的遗传物质保持相对稳定。减数分裂的前期I,细胞中的染色体发生了一系列特殊的变化——同源染色体联会、交叉互换和分离。每一对同源染色体中的两条染色体彼此分离,以后随机地分配到二个子细胞中去;异源染色体
(A) the relationship between meiosis and cytology, genetics Current “Biology” textbook “meiosis and germ cell maturation,” a section of textbook is an important section of the book, meiosis is a special mitosis . During meiosis, cells undergo two successive splits, while the chromosomes replicate only once, halving the number of chromosomes in the sex cells. The sex cells are then fertilized to form zygotes, and the number of chromosomes in the zygote returns to the number of chromosomes in the parental somatic cell so that the genetic material in the parental offspring cells remains relatively stable. In the early stage of meiosis, chromosomes in the cell undergo a series of special changes - homologous chromosome association, cross-exchange and separation. Two chromosomes in each pair of homologous chromosomes are separated from each other and then randomly assigned to two daughter cells; heterologous chromosomes