Tag: electrophoresis

Questions Related to electrophoresis

What is the function of gel electrophoresis in genetic engineering?

bio-chemistry biochemical techniques manipulation of dna electrophoresis isolation and separation of dna

  1. Cut DNA into many fragments

  2. Link together newly joined fragments of DNA

  3. Make millions of copies of a specific segment of DNA

  4. Separate fragments of DNA by their length and electrical charges

Show answer
Correct Option: D
Explanation:

Gel electrophoresis is a technique used to separate DNA fragments according to their size. DNA samples are loaded into wells (indentations) at one end of a gel, and an electric current is applied to pull them through the gel. DNA fragments are negatively charged, so they move towards the positive electrode. 

So, the correct option is 'Separate fragments of DNA by their length and electrical charges'.

DNA fragments generated by the restriction endonucleases in a chemical reaction can be separated by

bio-chemistry biochemical techniques manipulation of dna electrophoresis isolation and separation of dna

  1. electrophoresis

  2. restriction mapping

  3. centrigugation

  4. polymerase chain reaction

Show answer
Correct Option: A
Explanation:

Gel electrophoresis is a method for separation and analysis of macromolecules (DNA, RNA and proteins) and their fragments, based on their size and charge. It is used in molecular biology to separate a mixed population of DNA and RNA fragments by length, to estimate the size of DNA and RNA fragments or to separate proteins by charge.


Nucleic acid molecules are separated by applying an electric field to move the negatively charged molecules through a matrix of agarose or other substances. Shorter molecules move faster and migrate farther than longer ones because shorter molecules migrate more easily through the pores of the gel. This phenomenon is called sieving.

DNA Gel electrophoresis is usually performed for analytical purposes, often after amplification of DNA via polymerase chain reaction (PCR), but may be used as a preparative technique prior to use of other methods such as mass spectrometry, RFLP, PCR, cloning, DNA sequencing, or Southern blotting for further characterization.

So the correct option is 'Electrophoresis'.

A mixture containing DNA fragments, A, B, C and D, with molecular weights of A + B = C, A > B and D > C, was subjected to agarose gel electrophoresis. The positions of these fragments from cathode to anode sides of the gel would be 

bio-chemistry biochemical techniques manipulation of dna electrophoresis isolation and separation of dna

  1. D, C, A, B

  2. A, B, C, D

  3. C, B, A, D

  4. B, A, D, C.

Show answer
Correct Option: A
Explanation:
  • Shorter lengths of DNA move faster than longer lengths so move further in the time the current is run. So, since D has the heaviest weight (implying it has the longest strand), it will tend to remain far from the anode. B being a lightest fragment moves farthest from the cathode.
  • Hence The positions of these fragments from cathode to anode sides of the gel would be D, C, A, B,
  • So,the correct answer is 'D,C,A,B'.

DNA probe is used in:

bio-chemistry biochemical techniques manipulation of dna electrophoresis isolation and separation of dna

  1. Gel electrophoresis

  2. Northern blotting

  3. DNA finger printing

  4. Interferon synthesis

Show answer
Correct Option: C

DNA fragments generated by the restriction endonucleases in a chemical reaction can be separated by

bio-chemistry biochemical techniques manipulation of dna electrophoresis isolation and separation of dna

  1. Polymerase chain reaction

  2. Electrophoresis

  3. Restriction mapping

  4. Centrifugation

Show answer
Correct Option: B
Explanation:

A restriction enzyme (or restriction endonuclease) is an enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites. The DNA fragments are separated by electrophoresis, a process that involves application of an electric field to cause the DNA fragments to migrate into an agarose gel. The gel is then stained with a methylene blue stain to visualize the DNA bands and may be photographed. 

Thus, the correct answer is option B.

Read the passage and answer the following question.
Bacterial plasmid sequence: ATCCCA...1000 more nucleotides..... ..ATTAAGGCCTTACAGGACCCCGGAATGAGAGTA ATGGGCTATTCAGGTA... 2000 more nucleotides
Human DNA sequence: ATATCGTAATGTTGGTG..500 more nucleotides.. ..GTGTCAGGACGGGTGAAAGCCAGGACGCCGAATCG...5000 more nucleotides
The underlined DNA signifies the gene of interest were trying to clone Restriction enzyme sequences:
          ERA  I      GTAATG
          CRO  I     CAGGAC
           MEM II    GCCG
How many bands would show up on a 1 percent agarose gel if the plasmid was cut with both ERA I and CRO I?
bio-chemistry biochemical techniques manipulation of dna electrophoresis isolation and separation of dna

  1. 1

  2. 2

  3. 3

  4. 100

  5. 1,000

Show answer
Correct Option: C
Explanation:

CRO I has restriction sequence CAGGAC and ERA I has the restriction sequence GTAATG. When both the enzymes are used to cleave the bacterial and the human DNA, there are three fragments produced. So, only three bands will show up on the agarose gel as the restriction enzymes will cut very close. Thus, the correct answer is option C.

During isolation of genetic material, the chemical used to precipitate out the purified DNA is

botany biotechnology: principles and processes manipulation of dna electrophoresis isolation and separation of dna

  1. Bromophenol blue

  2. Chilled ethanol

  3. Ethidium bromide

  4. Both A and C

Show answer
Correct Option: B
Explanation:
The purified DNA, after treatment with various enzymes, precipitates out after addition of chilled ethanol. This is viewed as a collection of fine threads in the suspension, and is easily collected. The process is known as DNA spooling.
So, the correct answer is 'Chilled ethanol'.

Select the incorrect Statement regarding DNA replication with respect to the template strand

botany biotechnology: principles and processes manipulation of dna electrophoresis isolation and separation of dna

  1. Leading strand is formed in 5 $\rightarrow$ 3 direction.

  2. Okazaki fragments are formed in 5 $\rightarrow$ 3 direction.

  3. DNA polymerase catalyses polymerisation in 5 $\rightarrow$ 3 direction.

  4. DNA polymerase catalyses palymerisation in 3 $\rightarrow$ 5 direction.

Show answer
Correct Option: C
Explanation:

Since DNA polymerase requires a free 3' OH group for initiation of synthesis, it can synthesize in only one direction by extending the 3' end of the preexisting nucleotide chain. Hence, DNA polymerasemoves along the template strand in a 3'–5' direction, and the daughter strand is formed in a 5'–3' direction.

So, the correct answer is 'DNA polymerase catalyses polymerisation in 5 
→→ 3 direction'

The sequence of strategies involved in the isolation of a gene of interest from a plant cell during the process of rDNA technology

botany biotechnology: principles and processes manipulation of dna electrophoresis isolation and separation of dna

  1. Dissolution of biological membrane

  2. Enzymatic digestion of cell wall

  3. Precipitation of DNA

  4. Removal of DNA by spoiling

Show answer
Correct Option: C
Explanation:

Isolation of the Genetic Material (DNA):

Nucleic acid is the genetic material, which is present in all living organisms. In majority of organisms, this is present in the form of deoxy-ribonucleic acid (DNA). DNA must be present into pure form, i.e., free from other macro-molecules (like proteins, RNA, enzymes, etc.) in order to cut the DNA with restrictor enzymes.

Isolation of genetic material (DNA) is carried out in the following steps:

(a) Since the DNA is enclosed within the membranes, so, in order to release DNA along with other macro-molecules such as proteins, polysaccharides and lipids, bacterial cells/plant or animal tissues are treated with the enzyme lysozyme (bacteria), cellulose (plant cells), chitinase (fungus), respectively.

(b) RNA can be removed by the treatment with ribonuclease, whereas proteins can be removed by the treatment with protease.

(c) Other molecules can be removed by appropriate treatments and ultimately purified DNA will precipitate out, after the addition of chilled ethanol. This can be seen as collection of fine threads in the suspension.

So, the correct answer is “Precipitation of DNA”.

During the process of isolation of DNA, chilled ethanol is added to

botany biotechnology: principles and processes manipulation of dna electrophoresis isolation and separation of dna

  1. Break open the cell to release DNA

  2. Facilitate action of restriction enzymes

  3. Remove proteins such as histones

  4. Precipitate DNA

Show answer
Correct Option: D