Molecular Cytogenetic Technique- (Fish)

MOLECULAR CYTOGENETIC TECHNIQUE- (FISH)

Q. 1 Which of these is not a method for introducing genes into a cell?

 A

Transfection

 B

Electroporation

 C

FISH

 D

Recombination

Q. 1

Which of these is not a method for introducing genes into a cell?

 A

Transfection

 B

Electroporation

 C

FISH

 D

Recombination

Ans. C

Explanation:

Methods for introducing genes into a cell include, transfection (chemical based), electroporation (physical), infection (viral mediated) and recombination techniques.

 
Fluorescence in situ hybridization (FISH) is a cytogenetic technique that uses fluorescence-tagged probes to detect specific DNA sequences in tissue samples. It is not used for introducing genes into the cells.
 
Methods for genetic manipulation:
 
Transfection is the most commonly used method for introducing transgenes into human embryonic stem (hES) cells. This system is based on the use of carrier molecules that bind to foreign nucleic acids and introduce them into the cells through the plasma membrane.
 
Electroporation is a method that employs the administration of short electrical impulses that create transient pores in the cell membrane, allowing foreign DNA to enter into the cells. 
 
Infection is gene manipulation by viral infection which can produce a very high percentage of modified cells. Advantage over other systems are, high efficiency of DNA transfer (almost 100% efficiency) and single copy integrations.
Recombination occurs by physical exchange of DNA. An endogenous gene can be replaced by a transfected gene using homologous recombination. Recombination is the result of crossing-over that occurs at chiasmata and involves two of the four chromatids.
 
Ref: Human Embryonic Stem Cell Protocols By Kursad Turksen, 2006, Page 225

Q. 2 Rapid method of chromosome identification in intersex is:

 A

FISH

 B

PCR

 C

SSCP

 D

Karyotyping

Q. 2

Rapid method of chromosome identification in intersex is:

 A

FISH

 B

PCR

 C

SSCP

 D

Karyotyping

Ans. A

Explanation:

A i.e. FISH
FISH, chromosome painting and spectral karyotyping (SKY) are rapid methods of chromosome identificationQ.


Q. 3

Rapid method of chromosome identification in interphase is –

 A

FISH

 B

PCR

 C

SSCP

 D

Karyotyping

Q. 3

Rapid method of chromosome identification in interphase is –

 A

FISH

 B

PCR

 C

SSCP

 D

Karyotyping

Ans. A

Explanation:

 
FISH is a cytogenetic technique that can be used to detect the presence or absence of specific DNA sequences (specific gene locus) on chromosomes.
It uses fluorescent probes that bind to only those parts of the chromosome with which they show a high degree of sequence similarity.
Fluorescence microscopy can then be used to find out where the fluorescent probe bound to the chromosome.
FISH can be used for rapid identification of chromosome during interphase.
FISH can be used in metaphase cells to detect specific microdeletions beyond the resolution of routine cytogenetics or identify 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.

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