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Give two reasons why a scientist might want to extract human DNA.

2. Why do we need cells in order to do DNA extraction?
3. Describe how a cell, chromosome, and DNA relate to one another.
4. Why do we use cheek cells to gather DNA?
5. What are the names of the 4 steps to follow to purify DNA from a cheek swab?
6. What does “lysis” mean?
7. Why is a tube of water added to the micro-centrifuge along with the sample tube?
8. After using the centrifuge, where is the DNA in the sample tube?

1 answer

Sure! Here are the answers to your questions:

  1. Reasons for Extracting Human DNA:

    • Genetic Research: Scientists may want to extract human DNA to study genetic diseases, understand the genetic basis of certain traits, or explore human evolution.
    • Forensic Analysis: DNA extraction is crucial in forensic science for identifying individuals in criminal investigations or paternity testing.

  2. Need for Cells in DNA Extraction:

    • Cells are needed because DNA is housed within the nucleus of cells. To extract DNA, the cellular structure must be broken down to release the DNA from the nucleus and other cellular components.

  3. Relationship Between Cell, Chromosome, and DNA:

    • A cell is the basic unit of life that contains various components, including the nucleus. Within the nucleus, DNA is organized into structures known as chromosomes. Each chromosome is composed of a long strand of DNA that contains genes, the units of heredity.

  4. Use of Cheek Cells to Gather DNA:

    • Cheek cells are commonly used for DNA collection because they are easily accessible and can be obtained non-invasively through a simple swab. Additionally, these cells contain a sufficient amount of DNA for extraction and analysis.

  5. Four Steps to Purify DNA from a Cheek Swab:

    • Lysis: Breaking open the cells to release their contents, including DNA.
    • Precipitation: Adding alcohol (often ethanol or isopropanol) to separate the DNA from other cellular components.
    • Washing: Removing contaminants and impurities from the precipitated DNA.
    • Re-suspension: Dissolving the purified DNA in an appropriate buffer solution for storage or further use.

  6. Meaning of "Lysis":

    • "Lysis" refers to the process of breaking down or disintegrating cells, which allows the release of cellular contents, including DNA, into solution.

  7. Adding Water to the Micro-centrifuge:

    • A tube of water is often added to balance the centrifuge during operation. It helps maintain the stability and proper functioning of the centrifuge, preventing any imbalance that could lead to mechanical failure or inaccurate results.

  8. Location of DNA After Centrifugation:

    • After using the centrifuge, the DNA typically ends up in the form of a precipitate or a visible layer between the liquid and cellular debris at the bottom of the sample tube, or it may remain in the alcohol layer if it was precipitated out. The supernatant (the liquid above the solid residue) usually contains the remaining cellular components and impurities.

These answers provide a broad overview of the process and rationale behind DNA extraction, particularly using cheek cells.