• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9
  10. 10
    10
  11. 11
    11

Investigation into the varies stages of mitosis

Extracts from this document...

Introduction

Investigation into the varies stages of mitosis In my practical assessment I was observing nuclear division, mitosis and the stages involved in the process. Although in reality the process is continuous it has been divided into four stage called Prophase, metaphase, anaphase, telophase. Mitosis is the used for the replacement of cells and repair of tissues. It is also the basis of asexual reproduction. Prophase which is said to be the first stage of nuclear division or mitosis, is the stage where the centriole replicates just before hand and the chromosomes have started to coil up becoming shorter and thicker; they become more visible and stain more intensely. This is all in the early stages. In late prophase the centrioles move to opposite ends or poles of the nucleus, the nuclear envelope 'disappears' or it breaks up into small vesicles not visible by a light microscope. The nucleolus also disappears it forms parts of several chromosomes. Then at the end of prophase a spindle is formed. In metaphase each centriole reaches a pole they help to organise production of the spindle microtubules. The chromosomes line up along the equator of the spindle; they are attached by their centromeres to the spindle, which is made from protein microtubules. Each chromosome then splits at the centromere and is pulled apart then in the next phase, anaphase the chromotids (two identical sister chromatids make one chromosome) move to opposite poles, centromeres first, pulled by the microtubules. In the last suggested stage the nucleolus begins reforming as well as the nuclear envelope. The chromatids have reached the poles of the spindle; they will now uncoil again to form chromatin. Each chromatid contains one DNA molecule, which will replicate itself during interphase before the next division (interphase is another part of the cell cycle). Remains of the spindle are starting to break down, cytokinesis starts to take place this is division of the cytoplasm and cell into two by constriction from the edges of the cell. ...read more.

Middle

than those for other stages, therefore it could be that the prophase stage is longer because more things happen within the cell in the stage which has been classed as prophase in mitosis. In this information taken from the source shown late prophase is named as an almost separate stage prometaphase, it shows how much activity goes on in the cell in the stage of mitosis named prophase 1. Prophase * The two centrosomes of the cell, each with its pair of centrioles, move to opposite "poles" of the cell. * The mitotic spindle forms. This is an array of microtubules, synthesized from tubulin monomers in the cytoplasm, that develops from each centrosome. * The chromosomes become shorter and more compact. . Prometaphase * The nuclear envelope disintegrates. * A protein structure, the kinetochore, appears at the centromere of each chromatid. * With the breakdown of the nuclear envelope, spindle fibers attach to the kinetochores as well as to the arms of the chromosomes. The microtubules attached to a kinetochore exert tension on its chromatid. For each dyad, one of the kinetochores is attached to one pole, the second (or sister) chromatid to the opposite pole. Failure of a kinetochore to become attached to a spindle fibers interrupts the process. 3. Metaphase The tension is proportional to length; thus if a dyad approaches one pole, the tension in the opposite direction increases and the dyad is pulled back to an equilibrium position midway between the poles. In due course, all the dyads reach this position, the equatorial plane or metaphase plate. The chromosomes are at their most compact at this time. 4. Anaphase The sister kinetochores suddenly separate and each move to its respective pole dragging its attached chromatid (chromosome) behind it. Separation of the sister chromatids depends on the breakdown of the cohesins that have been holding them together. It works like this. ...read more.

Conclusion

My own results were found the most accurate way I thought possible. I made sure the same cells were not counted by using the microscope needle and a piece of paper to examine the next section of the slide I had not yet looked at by putting paper over the slide I had not yet looked at and counting abut 5 rows of cells, as the cells were arranged in fairly accurate rows. I am fairly sure I did not count the same cells more than once and my method was fairly accurate. However I do not know how others conducted their investigations and how they ensured reliability of their results. This puts a question mark over reliability of the overall results and also effects accuracy. The results should be fairly reliable as I have analysed results from 16 samples. The individual results do have a wide range varying from 3 up to 14 in the anaphase stage. This however as already stated could be due to individual differences (each slide contains different individual cells which gives rise to variation). Reliability could be improved by repeated investigation of the same slide then the error due misidentification or other errors can be judged and taken into consideration. Also each person doing the investigation should take the same steps to improve reliability e.g. How to ensure cells are not counted more than once. Perhaps when each cell is observed there should be a second check person if more than one person agrees that the cell is that particular stage of mitosis it is more likely to be correct. There is argument to suggest that my conclusion, that each stage of mitosis is not equal is fairly safe. However, there is also a lot of evidence to suggest that it is not very reliable i.e. I can only account for the reliability of my own results. To say my conclusion was completely safe I would have to do further investigational work taking the steps suggested to improve reliability. Linda Stevenson Mitosis ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Molecules & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Molecules & Cells essays

  1. Marked by a teacher

    Beetroot Practical Write up

    3 star(s)

    test tubes, this is because the beetroot at a 9mm only fits in a boiling tube where as the 8mm fits in a test tube. Since the concentrations have been lowered to the range between 0 and 25, with a gap of 5 between each, then only 5 boiling tubes shall be needed for each experiment hence 15 altogether.

  2. Marked by a teacher

    An investigation to examine the effects of temperature on membrane stability in beetroot, by ...

    3 star(s)

    * cuvettes * boiling tube rack There are no safety risks within this experiment, except the chance of scalding yourself on the hot water in the water baths. However, there is no need for protective gloves or safety spectacles as no dangerous chemicals are used.

  1. Catalyse Investigation

    It is also possible to do it without a funnel. The funnel is to prevent the pressure of the air being pushed into the burette from causing the pipe to pop off or oxygen to be leaked from the system (squeezed out).

  2. Mint and Garlic

    The fact that such a clear pattern is shown in the graph, allows me to feel confident in my results. I also feel confident in my results as it was repeated six times with averages taken. Certain limitations included the amount of times the experiment could be completed.

  1. An Investigation Into the Stages of Mitosis

    Nuclear division occupies around 5-10% of the complete cell cycle. There are four stages in the mitotic cell cycle: - Prophase, Metaphase, Anaphase and Telophase. The third phase - cell division - is when the cell itself divides into two by cytokineisis to form the two daughter cells.

  2. An investigation to find out about the features of mitosis in the root tip ...

    Use latex glove when using the dye. Watch glass with dye in. Could be dropped or knocked off desk spilling the dye. Keep watch glass in middle of desk. Razor blades. Possibility of cutting self or someone else. Use responsibly, and do not walk around with them for no reason.

  1. Respiration Assessment

    The Electron Transport Chain This final stage of respiration produces the largest number of ATP molecules. The electron transport chain consists of a series of carrier molecules, which will first accept an electron (and become reduced) and then lose it again (and become oxidised).

  2. Enzymes Investigation

    I will need to carry out some background information to find out what may affect my experiment. Background Information: An enzyme is a biological catalyst. They speed up the rate of a reaction however they are not affected themselves whilst doing this, this is why they are catalysts.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work