Cells are the smallest, most basic functional units that comprise living organisms. They are made up of smaller structures called organelles, which carry out different cell functions (for example, the mitochondria are responsible for respiration). Some ideas for cell science projects and activities include experimenting with salt and cell cytoplasm, examining cell nucleus and genome size, and extracting DNA from plant and animal cells.
SALT & CELL CYTOPLASM
All living cells have cytoplasm, which is a fluid-like substance (sometimes referred to as protoplasm) that cell bodies---such as mitochondria and ribosomes---float around in. In plant cells, the cytoplasm is contained both by an inner cell membrane, and an outer cell wall. As an experiment, you can observe the effect salt has on plant cell cytoplasm, assuming---of course---that it can penetrate the cell wall and membrane. According to crystal-clear-science-projects.com, you will need to take a small tissue sample from an onion and examine it under a compound microscope (100x magnification will be sufficient). You can then saturate your sample with a five percent solution of salt in water, observe, and do the same with a 10 percent solution. You may discover that the salt dissolves the cytoplasm of the cells in your onion, allowing you to have a better glimpse at the inner-workings of the plant cell.
CELL NUCLEUS & GENOME SIZE
Every species of animal stores DNA in the nuclei of its cells. However, some store more DNA than others, which correlates to a larger genome size. According to sciencebuddies.org, genome size is determined by weighing DNA, and is measured in picograms (one picogram equals one trillionth of a gram). For this experiment, you will determine if there is a correlation between the size of animal genomes and the size of their cell nuclei. To do this, you will need to utilize the Cell Size Database, which lists the genome sizes and nuclei sizes (measured in μm2, or in millionths of a square meter) of different animals. You will likely want to organize your results according to animal kingdom (for example, have a section for amphibians, mammals, etc.) and make a chart and/or graph to display them.
EXTRACTING DNA FROM PLANT & ANIMAL CELLS
This experiment will require equipment and chemicals that you may only be able to access at a high school or---perhaps more likely---university or college laboratory. According to usc.edu, your goal will be to determine if it is easier to extract DNA from an animal cell as opposed to a plant cell (which, as mentioned earlier, features a sturdy cell wall). You will need to take samples of animals and plants, such as small bits of chicken liver or onion, and prep them for extraction. This requires adding a buffering solution, a detergent and a neutralizing solution to each sample, and then subjecting each to a centrifuge (which rotates fluids at extremely high speeds). Finally, you need to add isopropanol to isolate and extract the DNA. For an additional twist on the experiment, treat plant samples with cellulase---which will breakdown cell walls---and see what effect this has on extraction.
The Difference of the Genomic DNA Extraction Between Animal & Plant
The structure of double-stranded DNA is universal in all living cells, but differences occur in the methods for extracting genomic DNA from animal and plant cells. Genomic DNA is found in the nucleus of cells. The amount and purity of extracted DNA depends on the type and size of the cell, as certain cells contain more DNA and impurities than others.
GENERAL DNA EXTRACTION
Plant and animal cells treated with a soapy substance will degrade the lipids in the cell and nuclear membranes. The DNA mixture will then separate from the cell membranes and proteins. The DNA in solution can be precipitated using alcohol. Depending on the amount in the sample, DNA may be visible by the naked eye. Such a simple procedure does not necessarily produce DNA of high purity.
PLANT AND ANIMAL CELLS
Plant cells are distinguishable from animal cells by their rigid cell wall and organelles like the chloroplast. They also contain proteins and enzymes that play a role in photosynthesis. Some plant cells are polyploidy, meaning they have more than one copy of each chromosome per cell. Cellular processes occurring in plants such as photosynthesis produce a range of secondary metabolites. Animal cells do not have a cell wall, but still need to be treated with chemicals like sodium dodecyl sulphate (SDS) to disrupt the cell membrane to release genomic DNA.
PLANT DNA EXTRACTION
Plant genomic DNA is more difficult to extract because of the plant's cell wall, which is removed by homogenization, or by adding cellulase to degrade the cellulose that makes up the cell wall. Also, the metabolites present in the plant cell may interfere with genomic DNA extraction by contaminating the DNA sample during the precipitation process.
ANIMAL DNA EXTRACTION
Peripheral blood leukocytes are a main source of animal genomic DNA, but sample collection is difficult as blood must be withdrawn from the animal. Blood contains a range of compounds like proteins, lipids, white blood cells, red blood cells, platelets, and plasma, which can contaminate the DNA sample. The primary contaminant of animal DNA extracted from blood samples is heme, the non-protein component of hemoglobin.
DIFFERENCES
The differences between plant and animal DNA lie in the sequence of bases in the helix. Compounds found in plant cells are absent in animal cells, and DNA base sequences reflect this, as the genomic plant DNA is often larger than animal DNA. These differences affect extraction methods, as it impacts on yield and purity of DNA.
GENERAL DNA EXTRACTION
Plant and animal cells treated with a soapy substance will degrade the lipids in the cell and nuclear membranes. The DNA mixture will then separate from the cell membranes and proteins. The DNA in solution can be precipitated using alcohol. Depending on the amount in the sample, DNA may be visible by the naked eye. Such a simple procedure does not necessarily produce DNA of high purity.
PLANT AND ANIMAL CELLS
Plant cells are distinguishable from animal cells by their rigid cell wall and organelles like the chloroplast. They also contain proteins and enzymes that play a role in photosynthesis. Some plant cells are polyploidy, meaning they have more than one copy of each chromosome per cell. Cellular processes occurring in plants such as photosynthesis produce a range of secondary metabolites. Animal cells do not have a cell wall, but still need to be treated with chemicals like sodium dodecyl sulphate (SDS) to disrupt the cell membrane to release genomic DNA.
PLANT DNA EXTRACTION
Plant genomic DNA is more difficult to extract because of the plant's cell wall, which is removed by homogenization, or by adding cellulase to degrade the cellulose that makes up the cell wall. Also, the metabolites present in the plant cell may interfere with genomic DNA extraction by contaminating the DNA sample during the precipitation process.
ANIMAL DNA EXTRACTION
Peripheral blood leukocytes are a main source of animal genomic DNA, but sample collection is difficult as blood must be withdrawn from the animal. Blood contains a range of compounds like proteins, lipids, white blood cells, red blood cells, platelets, and plasma, which can contaminate the DNA sample. The primary contaminant of animal DNA extracted from blood samples is heme, the non-protein component of hemoglobin.
DIFFERENCES
The differences between plant and animal DNA lie in the sequence of bases in the helix. Compounds found in plant cells are absent in animal cells, and DNA base sequences reflect this, as the genomic plant DNA is often larger than animal DNA. These differences affect extraction methods, as it impacts on yield and purity of DNA.
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