A medical researcher is trying to develop a diagnostic technique for a disease which is characterized by replication of a particular chromosomal region. What would be the most appropriate technique?

Question

A.  FISH
B.  Gene chip
C.  Genome sequencing
D.  White blood cell count

Clarify Question
  · What is the key concept addressed by the question?
· What type of thinking is required?

  Gather Content
· What do you already know about FISH and gene chip diagnostics?

  Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

  Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
 

Answer 1

A.  FISH

Clarify Question
  · What is the key concept addressed by the question?
        o This question addresses FISH and gene chip diagnostics.
· What type of thinking is required?
        o This question is asking you to take what you already know and apply it to this unfamiliar situation.

  Gather Content
· What do you already know about FISH and gene chip diagnostics?
        o Fluorescent in situ hybridization (FISH) takes advantage of the ability of DNA to be reversibly denatured and renatured. Hybridization uses a probe with either a fluorescent. In the case of FISH, the target DNA is an actual metaphase spread of chromosomes, or cells with intact chromosomes. This allows the detection of gross chromosomal abnormalities, such as large deletions, inversions, duplications and translocations.
        o Gene chips also known as DNA microarrays, are collections of hundreds to thousands of different DNA sequences that are spotted onto a solid surface such as a microscope slide. The DNA sequences are usually short chemically synthesized pieces of DNA, or short sequences of DNA amplified by PCR or RT-PCR. Biomarkers can be diagnostic of a disease state, be informative about the progress of a disease, or help monitor the response to therapy. In the case of gene chips, the biomarker is the mRNA synthesized from a particular gene. For example, individuals with certain autoimmune diseases or chronic inflammatory conditions will express different sets of genes in immune cells than will healthy individuals. Gene chips can be used to determine which genes are being expressed and the relative levels of expression for different genes.

  Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Since the disease is characterized by a gross chromosomal abnormality, FISH is the best technique to use here.
        o Whole genome sequencing would work as well, but is too complex and expensive. FISH is more practical.

  Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that the best technique for recognizing a chromosomal duplication is FISH, because there would be an extra fluorescent spot present?