In everyday life, we never think about the amount of cells that we shield or produce; least the structure, size or shape. Often in forensic investigation, scientists come across different types of cells, especially human cell (like spermatozoa cell, while investigating an alleged rape) or human fluid (like bacteria, which could be found in the blood and use for DNA profiling. ) These cells can help investigators to know more about a case for example, pollen and diatoms could help a scientist to decide the geographical area of an incident.
If it is underwater, Diatoms would be found or land (pollen). It can help to decide the type of environment an incident occurred. Cells can also help to explain if an evidence or body has been transported from one place to the other, i. e. it helps to locate the original crime scene. For example, if a body was found in the bush, after experimentation, scientist might found out that the body has been transported from one place to another, if there is diatoms in the body, it might identify the movement of corpse.
According to Clegg (2000) Cell is the fundamental unit of life. This means that cells are the smallest part of any living thing; they serve as the basic building blocks of life that make up the structural and functional unit of all living organism. ‘They contain the hereditary information, which is necessary for regulating cell functions and for transmitting information to the next generation of cells’. Alberts, 2002 chp21) This means that all living things are made of cells, which are produced from pre-existing cells, and they carry hereditary trait from one generation of a family to the next. All organisms consist of one (unicellular organism, e. g. euglena and chlorella) or more cells (multicellular organism, e. g. mammals and flowering plants). Cells are too small to be seen with the naked eye, so a microscope (light microscope or electron microscope) is required to view the structure.
Most cells consist of cytoplasm, (the enzymes that control all the chemical reaction in the cell), nucleus (it contains the genetic material which codes for all the proteins that the cell makes; and it controls everything that happens in the cell) and plasma membrane (which controls the movement of substances in and out of the cell. It also serves as attachment for the cell wall and the intracellular cytoskeleton, that is, it also holds the cells together. ) There are some differences between plant and animal cells.
Plants cells consist of cell wall, (which support the cell and it is made up of cellulose. ) chloroplast (it contains chlorophyll, which trap light for photosynthesis) and large vacuole (contain cell fluid for storage and support). While animal cell is surrounded by plasma membrane and contain a nucleus; it has no cell wall, chloroplast and large permanent vacuole; it store carbohydrate as glycogen, while plant store it as starch; and it has a centriole, which is present outside the nucleus. (Dawson and Honeysett, 2001)
Thorpe (1984) explains that cells can be divided into two major classes (the eukaryotic cells and the prokaryotic cells), and the difference between them is in the basis of their cell organisation. The prokaryotic cells are found in single celled organism like Bacteria and Archaea; they do not have any nucleus or organelles which are in the membrane, but contain a single, circular chromosome in the cytoplasm. Their DNA travels openly round the cell and they reproduce by binary fusion, which is the process of replicating the original cell to produce two identical cells.
Prokaryotic cells are identified with water pollution and spoilage. While The eukaryotic cells are found in all plants, animal, fungi and protoctist. They are multicelled organism and reproduce in different ways (e. g. mitosis, meiosis). The surrounding cytoplasm contain many different membranous organelles, for example, fungi posses wall but are not photosynthetic; chloroplast is possessed by some protozoa but they have no wall; likewise some multicellular form don’t have organs and other differentiated tissue.
The aim of these experiment is to develop our knowledge and understanding on cells by knowing the significance of the use of cell and assess the importance of cell as an evidence in forensic cases (e. g. cells are used in DNA profiling); by being able distinguish between different cell types and their characteristic; using the microscope to examine different cell types and explaining the difference between them, especially in their size, colour and structure.
This experiment also aims to build our confidence in using the microscope and improve our ability to calibrate a microscope to relevant sizes Method During this experiment, six different cell types (spermatozoa smear, squamous epithelium cells, pollen grain, diatoms mixed, bacillus subtilis, ; human blood) were examined using a high power light microscope, which allows individual cells and some of their structure (e. g. nuclei,) to be seen. The advantage of this method is that it allows us to examine living cells and tissues, i. . to know the size, colour, structure and the different between various cells. The disadvantage is that it has a limited resolution; that is it does not have the ability to distinguish between objects that are close together.
This is a disadvantage because two different cells might be joined together and due to the limited resolution of the microscope, we might not be able to view them. The microscope was first calibrated before the cells were examined, i. e. stage micrometer was placed on the microscope stage, placing one side of the dark circle directly under the objective lens (x40 objective); when the microscope stage was at its highest point and was viewed through the eyepiece, the large focusing knob was use to move the stage downwards slowly until the line of the circle came to view, then the adjusted knob was use to clearly focus on the line and the stage micrometer was moved across until one could see the stage scale clearly (two scales was seen) , then, the stage micrometer was move across until the edge of the scale was in line with the eyepiece scale.