Question

Exercise 1 Explaining Mitosis In this exercise, you will describe stages of mitosis in an animal cell. Procedure 1 Describe the process of prophase in Data Table 1. 2 Repeat step 1 for the remaining steps of mitosis: prometaphase, metaphase, anaphase, telophase, and cytokinesis, Exercise 1 - Questions 1. Describe the process of the mitotic spindle and microtubules throughout the steps of mitosis. в то Ет т. O Words

Answer 1

Prophase: it is the first stage of mitosis.  At this phase, the chromosomes are still enclosed in the cell nucleus within the nuclear envelope. The chromosomes also contain a centromere.  Late in prophase, kinetochores assemble on the centromeres. Specialized microtubules, called kinetochore microtubules later attach to these sites. condensed centrosomes, which are the organizing centers of microtubules, begin to separate towards opposite poles of the cell. The network of cytoskeletal components begins to break down and the mitotic spindle forms. The mitotic spindle is an arrangement of microtubules that is responsible for aligning duplicated chromosomes in later phases.

prometaphase: prometaphase is started by the breakdown of the nuclear envelope into small vesicles. Kinetochores also become fully matured on the centromeres of the chromosomes. Chromosomal material condenses to form compact mitotic chromosomes. Chromosomes are seen to be composed of two chromatids attached together at the centromere. Initiation of the assembly of mitotic spindle, the microtubules, the proteinaceous components of the cell cytoplasm help in the process. the cell organells like golgi complexes, endoplasmic reticulum, nucleolus and the nuclear envelope are desentegrated at the end of the stage.

Metaphase: at this stage, condensation of chromosomes is completed and they can be observed clearly under the microscope.morphology of chromosomes is mostly studied at this stage. metaphase chromosome is made up of two sister chromatids, which are held together by the centromere. Small disc-shaped structures at the surface of the centromeres are called kinetochores. These structures act as the sites of attachment of spindle fibres to the chromosomes that are moved into position at the centre of the cell. the metaphase is characterised by the formation of metaphase plate. Spindle fibres attach to kinetochores of chromosomes. The  Chromosomes are moved to spindle equator and get aligned along metaphase plate through spindle fibres to both poles. it is called metaphase plate

Anaphase: During anaphase each chromosome arranged at the metaphase plate is split simultaneously and the two daughter chromatids starts to move towards the two opposite poles. While the centromere of each chromosome pulling the centrosome to the pole, Centromeres split and chromatids separate and  Chromatids move to opposite poles.

Telophase: it is the final stage of mitosis. the chromosomes that have reached their respective poles decondense and lose their individuality.Chromosomes cluster at opposite spindle poles and their identity is lost as discrete elements. Then Nuclear envelope assembles around the chromosome clusters and Nucleolus, golgi complex and ER are generated.

Cytokinesis: it is the division of the cytoplasm to form two new cells. there are different mechanisms for cytokinesis in plant and animal cells. In an animal cell, this is achieved by the appearance of a furrow in the plasma membrane. The furrow gradually deepens and ultimately joins in the centre dividing the cell cytoplasm into two. In plant cells, wall formation starts in the centre of the cell and grows outward to meet the existing lateral walls. The formation of the new cell wall begins with the formation of a simple precursor, called the cell-plate that represents the middle lamella between the walls of two adjacent cells. At the time of cytoplasmic division, organelles like mitochondria and plastids get distributed between the two daughter cells. In some organisms karyokinesis is not followed by cytokinesis as a result of which multinucleate condition arises leading to the formation of syncytium.