Separation of DNA Fragments by Electrophoresis- Pharmacognosy & Phytochemistry
1.Which of the following cannot be used forthe separation of nucleic acids?
A. SDS â€“ PAGE
C. Northern blotting
Explaination: Sodium dodecylsulphate is a detergent, often used in biochemical preparations, bindsto proteins and causes them to form a rod like structure. Most proteins bind SDS in the same ratio (1.4g per g of protein). Thus,the electrophoresis of proteinsin an SDS â€“containing polyacrylamide gelse parates them in order of their molecular masses. It is not known to have the similar effect on nucleic acids
2. The polymerization ofthe gel used in PAGE occurs between polyacrylamide and ______
C. Nâ€“ methyleneacrylamide
D.N,Nâ€“ methylene bisacrylamide
Explaination: In PAGE, polyacrylamide gel electrophoresis, gel is made by free radical by polymerizing the monomers
together. The two major monomers between which the polymerization occurs are polyacrylamide and N,Nâ€“ methylene bisacrylamide in the buffer of choice.
3. If DNA is digested by endonucleasesin four sites giving rise to fragments of which two are equal in length how many bands would be seen after electrophoresis?
Explaination: Digestion atfoursites givesrise to five fragments. Two fragments are of same size thus they will form a single band. Therefore only four bandsis observed.
4. The fluorescent dye such Ethidium is used for visualizing DNA. How do ethidium bindsto DNA?
A. Stacked between histone molecules
B. Bindsto the nucleotide base
C. Intercalated between the stacked bases
D. Bindsto the phosphodiester backbone
Explaination: Ethidium is intercalated between the stacked bases. This in creases the spacing of successive base pairs, distorts the regular sugar phosphate back bone and decreasesthe twist of the helix.
5. Pulse field gel electro phoresisse parates DNA molecules of size _______
A.10 â€“ 20 bp
B. 20 â€“ 30 Kb
C. 30 â€“ 50 Kb
D. 40 â€“ 50 bp
Explaination: DNA molecule sranging from 30 â€“ 50 kb migrate in a snake like mannerthus,cannot be readily be resolved. These long DNA scan be separated by changing the orientation of the electric field. This process of separation is known as PFGE.
6.Which ofthe following will migrate faster? The condition isthe molecular weight ofthe following is equal.
A. Supercoiled circular DNA
B.Nicked circular DNA
C. Single stranded DNA
D.Double stranded DNA
Explaination: Super coiled circular DNA has a less effective volume than the others. Thus, it migrates more rapidly when subjected to electro phoresis due to its compact structure.
7.Agarose can be extracted from which ofthe following?
B. Lycazusican esculentum
C. Ficum benghalensis
Explaination: As we know agarose is extracted from seaweeds. Precisely two types of species are used for the extraction; they are the Gracilaria esculentus and Gelidium nudifrons.
8. Electrophoresiscannot be used to separate __________
C. Amino acid
Explaination: DNA, RNAand protein can be separated by the by the method of electrophoresis as it can be separate charged molecules.Amino acids are generally separated by the process of chromatography.
9.Which of the following is not a character of polyacrylamide gel?
C. Stable over a wide range of pH
D. Separate upto a few 100 bp ofDNA
Explaination: The pore size of polyacrylamide gel is very small due to high resolution power. Thus, itcan separate DNA fragments upto a few 100 base pairs only.
10. Pulse field gel electrophoresis was developed by _______
A. Collins and John
B. Kary Mullis
C. PatrickOâ€™ Farrell
D. Schwartz and Cantor
Explaination: PFGE was developed by Schwartz and Cantorin 1984. This mechanism was developed to separate molecules as long as10 Mb in an agarose gel.