Principles of Life 3e Student Resources is no longer available and it was replaced by Biology and Life Sciences.
Animation 12.4 DNA Testing
INTRODUCTION
Many techniques exist for testing whether a sample of DNA carries a mutation. In this animation, we explore the use of two different techniques for identifying whether an individual carries the sickle-cell allele of the β-globin gene.
One procedure is called allele-specific oligonucleotide hybridization. In allele-specific oligonucleotide hybridization, the binding of a probe to sample DNA indicates that a particular allele is present in the DNA.
The other procedure, DNA testing by allele-specific cleavage, uses restriction enzymes as diagnostic tools. Restriction enzymes are proteins that recognize and cut DNA at specific sequences. Allele-specific cleavage relies on the mutation in the disease allele either adding or eliminating a recognition site for a restriction enzyme.
Please note: If you have been assigned this activity by your instructor, you must complete it within LaunchPad (or your school's learning management system) in order to receive credit.
Textbook Reference: Key Concept 13.4 Selection Can Be Stabilizing, Directional, or Disruptive, p.322
CONCLUSION
Allele-specific oligonucleotide hybridization is a widely used test that allows researchers to distinguish between two alleles that differ by a single nucleotide. The oligonucleotide probes are created so that each type hybridizes to DNA from just one of the alleles. Another probe hybridizes to a second allele. The probes need to be perfectly matched to the alleles, because a single mismatch will prevent hybridization of the probe to the DNA.
DNA testing by allele-specific cleavage uses restriction enzymes as diagnostic tools. In the example of sickle-cell anemia, the mutation that causes the disease also eliminates an MstII recognition site from the mutated β-globin gene. For this reason, the allele-specific cleavage test can be used to determine a person's genotype. However, many mutations that cause disease do not affect the recognition sites of restriction enzymes, thereby limiting the use of this particular technique in diagnosing disease.