what is the easiest and best way to determine which phase of mitosis a cell may be in?
Objectives:
• To understand the process and different stages of mitosis.
• To visualize different phases of mitosis.
Theory
A process by which a parent prison cell divides into two or more daughter cells is called cell division. Jail cell segmentation is a modest role of the cell cycle. In normal eukaryotic cells, the blazon of cell segmentation is known as mitosis.
Another type of cell division is present in reproductive cells of eukaryotes and is known as meiosis. Prison cell cycle is mainly classified into two segments: M-phase and Interphase. Interphase is the longer menstruation of cell division. During this stage the cell prepares for its next stage.
This is a period of diverse activities and these activities are a prerequisite for the next mitotic stage. Interphase is mainly divided into 3 phases: G1 stage, Southward phase and G2 phase. Due south stage is the flow of replication. G1 and G2 are the two gap phases during which the cell grows, producing proteins and preparing the cells. These phases also have certain cheque points and the whole cell bike is strictly regulated.
M phase of the cell bike stands for Mitosis or nuclear division. In eukaryotes, Dna replication is followed past a procedure called mitosis which separates the chromosomes in its cell nucleus into two identical sets, in two individual nuclei.. Mitosis is followed by cytokinesis. The process of Mitosis is divided into four stages: Prophase, Metaphase, Anaphase and Telophase.
Prophase: During this stage, the chromosomes super coil, condense and become visible for first fourth dimension during the cell bicycle. The spindle fibers start forming. The nuclear membrane starts disintegrating.
Metaphase: During this stage, the spindle fibers reach and attach to centromere of each sis chromatids. The chromosomes align along the center aeroplane of the prison cell. The nuclear membrane disintegrates completely.
Anaphase: During this stage, the centromeres showtime splitting and the sis chromatids begin to migrating towards the contrary poles of the prison cell.
Telophase: During this phase, the chromosomes are amassed on the either end of the prison cell. The nuclear membrane starts reforming. The prison cell plate (new jail cell wall) starts to form betwixt the two daughter nuclei. This will be followed by cytokinesis.
Mitosis in Onion Root Tip
The genetic information of all organisms resides in the individual Dna molecules or chromosomes. An onion prison cell possesses eight chromosomes lwhereas homo cells possess forty six chromosomes.
In 1842, C. Nägeli first saw chromosomes and in 1888 W. Waldeyer named them. Walther Flemming studied and named the process of cell partition as mitosis. Cell division occurs rapidly in growing root tips of sprouting seeds or bulbs.
The most commonly used root tips in labs to report mitosis are onion, wheat, lentil, barley and alfalfa. An onion root tip is a quickly growing part of the onion and thus many cells will exist in different stages of mitosis. The onion root tips can exist prepared and squashed in a way that allows them to be flattened on a microscopic slide, so that the chromosomes of individual cells can exist observed easily. The super coiled chromosomes during dissimilar stages of mitosis nowadays in the onion root tip cells can be visualized past treating with Deoxyribonucleic acid specific stains, like Feulgen stain and Acetocarmine stain.
Mitosis in Onion Root Tip
Mitotic Index
The percentage of cells undergoing mitosis or it is defined every bit the ratio of no. of cells in the dividing stage to the full number of cells observed. This will assist to place the region of almost mitotic activities. Mitotic index helps united states to quantify the cell partition. Mitotic index decreases with increasing distance from root tip. That means gradual decrease in cell division as information technology moves from the zone of cell division to the zone of cell elongation. The meristematic region in the root tip is the actively growing region and thus the mitotic alphabetize is loftier.
Mitotic index = due north/N × 100
Mitotic index is used to quantify the differences in jail cell division when environmental parameters are inverse. Studies have already proved that, the plants grown in space in microgravity accept a greater mitotic alphabetize than plants grown on the ground. The gravity sensing signals in the root cap are unable to send proper orientation signals which inhibit growth in the cells that are distant from the root tip and root cap junction when kept in zero gravity. This leads to mitosis in greater number of cells and plants also produce secondary roots at a high charge per unit.
Karyotype and Karyotype Analysis
A karyotype is a technique that allows researchers to visualize the chromosomes under the microscope with the assistance of proper extraction and staining techniques. The karyotype is an organized profile of an organism's chromosomes arranged in pairs. In a karyotype, the chromosomes are arranged and numbered, based on size from largest to smallest, centromere position and banding design (due to staining) of chromosomes. This technique helps scientists identify any chromosomal abnormalities and alterations that may result in genetic problems and disorders.
Karyotype of any organisms is obtained hands by serious of modest steps. For that, first simulate the jail cell division of the cells. After simulating the cell sectionalization, the cells are arrested by cholchine handling at metaphase stage of the prison cell division by preventing the formation of spindle fibers. The chromosomes shorten and become more tightly coiled making their shapes more distinct and become more visible under the light microscope during the metaphase stage of the jail cell division.
This cholchine treated cell mixture is centrifuged and the resulting pellet is immersed in a hypotonic solution that causes the cell to swell and and so allows more space for chromosomes to spread. So a fixing amanuensis is applied on the jail cell to freeze the chromosomes from moving and a stain is used to visualize the chromosomes and their banding pattern. A photo of the chromosomes is taken, cut, paired and rearranged to requite a karyotype.
Karyotype of Human Male person and Female
The karyotype analysis displays the banding pattern of the chromosomes. This banding design allows scientists to recognize specific parts of the chromosomes and to place the deletions and translocations that occurred in the chromosomes. This helps to identify different genetic disorders in humans and other organisms. The number, shapes and sizes of the condensed chromosomes vary for each species then the closely related species can be distinguished from each other.
In club to perform onion root tip karyotype analysis, the process is a niggling unlike and less complex from the above one since this is a plant source. The onion roots were grown in water and its tips were subsequently cut off and fixed in 3:1 ethanol: glacial acectic acrid.
The sample is then stained with Deoxyribonucleic acid specific stains like Acetocarmine or Feulgen stain in acectic acrid and was subjected to squash method. Then the sparse layer of jail cell squash on the slide was viewed under the low-cal microscope. Then the cell was photographed and documented. By using actively dividing cells in the onion root tip, this experiment aims to obtain a karyotype from the sample and to determine the purpose of each step used in the procedure.
Karyotype of Onion Root Tip Jail cell
Source: https://vlab.amrita.edu/?sub=3&brch=188&sim=1102&cnt=1
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