![]() The homologous chromosomes reach the pole of the spindle apparatus.The connection between the sister chromatids degrades near the arms but remains unharmed in the centromere.Homologous chromosomes are pulled towards the poles of the spindle apparatus by the shortening of the kinetochore microtubules.Similar to mitosis, kinetochores act as the bridge between chromosomes and the microtubules of the spindle apparatus.Homologous chromosomes arrange in the equatorial region in the completely formed spindle apparatus.Four parts of the tetrads and the chiasmata are prominently visible in this sub-stage. Diakinesis: Condensation of chromosomes continues nuclear membrane and nucleolus disappears and formation of spindle apparatus begins.The chiasmata remain intact until Anaphase I. Diplotene: The synapsis becomes weak and the linkage of the chromatids starts to break causing separation.In this region, the non-sister chromatids sometimes exchange their parts in a process called Crossing Over. Pachytene: Two non-sister chromatids form a physical linkage, the site of which is known as Chiasmata.The paired chromosomes are called bivalent or tetrad. Zygotene: Homologous chromosomes are formed and they pair up with another homologous chromosome by a process called synapsis.Leptotene: This is a comparatively short stage where progressive condensation of chromosome fibers take place.This is the longest and most complex stage of Meiosis I and is again divided into 5 sub-stages:.There are 4 sub-phases under Meiosis I which are as follows:.Similar to Mitosis, before Meiosis I starts, the cell undergoes Interphase where it grows in G1 subphase, chromosomes replicate in S phase and synthesize necessary chemicals for carrying out different sub-phases under Meiosis I and Meiosis II.In case of meiosis, the chromosomes divide once while the nucleus undergoes division twice.Meiosis is rather divided primarily into two phases which are a) Meiosis I and b) Meiosis II both of which have sub-phases. Also known as “Reductional Division” since the number of chromosomes reduce to half, the preparatory steps for meiosis cell division are similar to that of mitosis. ![]() The process of cell division in which one mother cell divides into four daughter cells having half the number of chromosomes in the mother cell.Nucleolus, the part of the cell where ribosomes are produced disappears.The spindle fibres attach to the condensed chromosomes and help in their movement and distribution during the latter phases of cell division. Formation of a spindle shaped apparatus made from microtubules initiates which is often called Mitotic Spindle.The 5 phases of Mitosis cell division are:.G2 (second gap) – Immediate phase after DNA Replication where cells synthesize materials required for the formation of spindle fibre during the different phases of Mitosis.S (synthesis) – In this sub-phase, DNA packed in chromosomes are replicated so that complete set of information are passed on from the mother cell to the daughter cells which will be generated during Mitosis.G1 (first gap) – Cells synthesize a number of materials that are required for completing replication in the following steps including some enzymes, regulators and nutrients.There are 3 sub-phases which altogether build up the Interphase stage. It is a segment of the cell cycle before Mitosis where a cell prepares itself for division.This subphases are necessary for a cell to prepare beforehand it actually goes under division. The principle phases of Mitosis cell division are preceded by a major phase known as Interphase which has a collection of subphases.Also known as “Equational Division” because of the equality in the number of chromosomes in mother and daughter cells “Karyokinesis” relating to the fact of the occurring nuclear division.The biological process in which one mother cell is divided into two identical daughter cells having the same number of chromosomes.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |