![]() Pairing of chromosomes occurs in a zipper-like fashion.Synapsis is facilitated by the assembly synaptonemal complex. One of the distinguishing features of this stage is synapsis of homologous chromosomes.This stage is known as bouquet stage, as telomeres cluster at one end of the nucleus. During this stage, chromosomes line up to form homologous chromosome pairs.The word zygotene means ‘paired threads’ in Greek. A centrosome with centriole is situated near pole of the nucleus.This stage is of very short duration with characteristic condensation and coiling of the chromosomes.The two sister chromatids are so tightly bound that they are not distinguishable from one other.During this stage two sister chromatids of the duplicated chromosomes condense into long thin strands clearly visible within the nucleus.The following are the main features of this stage, Leptotene: The word leptotene means ‘thin thread’ in Greek. Homologous recombination of DNA which occurs in Meiosis I, results in significant genetic variations. During prophase I, chromosomal cross over occurs resulting in homologous recombination whereby DNA is exchanged between homologous chromosomes. It is the first and longest stage of meiosis I. Meiosis I consists of four stages namely, Hence meiosis-I is referred to as a reductional division.įor example, a diploid human cell contains 46 chromosomes is 2n, because it contains 23 pairs of homologous chromosomes. The first meiotic division reduces the ploidy of original cell. The resulting daughter cells contain one entire haploid set of chromosomes. In Meiosis I, the pairs of homologous chromosomes, made up of two sister chromatids are split into two cells.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |