Ans is a. ie. FISH * The above-mentioned site writes about FISH- * "FISH can be used in interphase cells to determine the chromosome number of one or more chromosomes as well as to detect some specific chromosome rearrangements that are characteristic for certain cancers. The primary advantage of interphase FISH is that it can be performed very rapidly if necessary, usually within 24 hours, because cell growth is not required.* A good example is the Aneuploid Screen test which is performed on amniotic fluid cells when there is a strong clinical indication for one of the common trisomies. The sample nuclei are denatured and hybridized with DNA probes for chromosomes 13, 18, 21, X, and Y and results usually obtained within 24 hours. Routine Cytogenetics is included with an Aneuploid Screen to confirm the results or detect any abnormalities not detected by interphase FISH."Fluorescent IN SITU Hybridization (FISH)Fluorescent In Situ Hybridization (FISH) is a relatively new technology utilizing fluorescently labeled DNA probes to detect or confirm gene or chromosome abnormalities that are generally beyond the resolution of routine cytogenetics. The sample DNA (metaphase chromosomes or interphase nuclei) is first denatured, a process that separates the complementary strands within the DNA double helix structure. The fluorescently labeled probe of interest is then added to the denatured sample mixture and hybridizes with the sample DNA at the target site as it reanneals (or reforms itself) back into a double helix. The probe signal can then be seen through a fluorescent microscope and the sample DNA scored for the presence or absence of the signal.FISH can be used in metaphase cells to detect specific microdeletions beyond the resolution of routine cytogenetics or identify the extra material of unknown origin. It can also help in cases where it is difficult to determine from routine cytogenetics if a chromosome has a simple deletion or is involved in a subtle or complex rearrangement. In addition, metaphase FISH can detect some of the specific chromosome rearrangements seen in certain cancers.Microdeletion Syndromes Currently Diagnosable with FISHCri-du-Chat * Kallman SyndromeMiller-Dieker Syndrome * Williams SyndromeSmith-Magenis Syndrome * Wolf-HirschhornSteroid Sulfatase Deficiency * Prader-Willi/Angelman SyndromeDiGeorge/Velo-Cardio-Facial/CATCH-*22/Shprintzen SyndromeSingle-stranded conformation polymorphism (SSCP)SSCP is the electrophoretic separation of single-stranded nucleic acids based on subtle differences in sequence (often a single base pair) which results in a different secondary structure and a measurable difference in mobility through a gel.The mobility of double-stranded DNA in gel electrophoresis is dependent on strand size and length but is relatively independent of the particular nucleotide sequence. The mobility of single strands, however, is noticeably affected by very small changes in sequence, possibly one changed nucleotide out of several hundred. Small changes are noticeable because of the relatively unstable nature of single-stranded DNA; in the absence of a complementary strand, the single strand may experience intrastrand base pairing, resulting in loops and folds that give the single strand a unique 3D structure, regardless of its length. A single nucleotide change could dramatically affect the strand's mobility through a gel by altering the intrastrand base pairing and its resulting 3D conformation (Melcher, 2000).Single-strand conformation polymorphism analysis takes advantage of this quality of single-stranded DNA. SSCP analysis offers an inexpensive, convenient, and sensitive method for determining genetic variationThe SSCP analysis method detects point mutations by analyzing their unique electrophoretic mobility that results from small changes in the variant's nucleotide sequences.Polymerase chain reaction is a sensitive and rapid method for amplifying a specific DNA sequence.