L A B S A F E T Y
The National Association of Biology Teachers recognizes the importance of laboratory activities using human body samples and has developed minimum safety guidelines to minimize the risk of transmitting serious disease. ("The Use of Human Body Fluids and Tissue Products in Biology," News & Views, June 1996.) These are summarized below:
The mouthwash method of DNA isolation does generate liquid waste; however, the risk of spreading an infectious agent is much less likely than from natural atomizing processes, such as coughing or sneezing. Several elements further minimize any risk of spreading an infectious agent that might be present in mouthwash samples:
Consent and Confidentiality
Student particpation in this experiment raises real-life questions about the use of personal genetic data:
There is concensus that a human DNA sample should be obtained only with the willing consent of a donor, who understands the purpose for which it is being collected. Thus, the experiments should be explained ahead of time and students given the option to refrain from participating. (Some teachers may wish to have parents sign a consent from, such as those filled out for a field trip.) There is also consensus that a DNA sample be used only for the express purpose for which it is collected. Thus, student DNA samples should be thrown away after completing the experiments in this unit. (In fact, the cheek cell samples are not stable enough for long term storage.)
The Alu PV92 insertion and mt control region polymorphisms used in these experiments were specifically selected because they are phenotypically neutral. Neither locus encodes a protein, nor has any known relationship to disease states, sex determination, or any other phenotype.
Even though there is no chance of disclosing phenotypic information about the experimenters, all student polymorphism data stored at our Allele Server and Sequence Server sites are anonymous. Online submission forms identify students only by number and have no entry fields for personal identifiers. We recommend that each student select a four-digit personal identification number (PIN) and label their experiment with this number. Under this system, there is no chance that a student can ever be linked to his/her sample in the database. Alternately, students can be assigned a sequential number, with no permanent key maintained by the teacher.
All polymorphisms are inherited in a Mendelian fashion and can give indications about family relationships. The PV92 polymorphism has an inherently low information content – usually there are at least several parental genotypes that could account for an observed student genotype. On the other hand, mitochondrial (mt) DNA genotypes are explicit records of maternal inheritance that are usually unique to each family. Since mt DNA is inherited exclusively from the mother, there is no chance of showing nonpaternity, which is the most frequent problem uncovered by DNA testing. However, inconsistent mt DNA types between siblings and/or mother could suggest adoptive situations.
To avoid the possibility of discovering inconsistent mt DNA inheritance, we recommend that you do not generate genotypes from family members. However, in a formal sense, a single data set – even for mt sequence – cannot definitively prove or disprove relatedness for several reasons:
DNA Learning Center, Cold Spring Harbor Laboratory
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