Tag: bio-chemistry

Questions Related to bio-chemistry

When heated, the hydrogen bonds between the complementary strands of DNA break and the 2 strands separate in a process called melting. Which of the following pieces of DNA will require maximum temperature for melting?

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

  1. $3'\quad AAGGTATACAAT\quad 5'\ 5'\quad TTCCATATGTTA\quad 3'$

  2. $3'\quad GAGCUAUCCGAG\quad 5'\ 5'\quad CUCGAUAGGCUC\quad 3'$

  3. $3'\quad ACGTCCGCTGCG\quad 5'\ 5'\quad TGCAGGCGACGC\quad 3'$

  4. $3'\quad ATTAGCTAGCAA\quad 5'\ 5'\quad TAATCGATCGTT\quad 3'$

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Correct Option: A

E.coli which was grown in the medium containing heavy isotope $ {  }^{ 15 }{ N }$ for several generations is shifted to normal $ _{  }^{ 14 }{ N }$ medium, the percentage of DNA strands with $ _{  }^{ 14 }{ N }$ isotope after two generations is _____________.

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

  1. $12.5$%

  2. $50$%

  3. $75$%

  4. $100$%

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Correct Option: A

When a sample containing antibody $1\ gM$ is run on SDS - PAGE, what molecular weight bands are expected to be seen?

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

  1. $70, 55. 15\ Kbp$

  2. $50, 15\ Kbp$

  3. $50, 55\ Kbp$

  4. $50, 25\ Kbp$

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Correct Option: A

Which of the following is not a technique for introducing recombinant DNA into host cells?

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

  1. Infection by Agrobacterium

  2. Microinjection

  3. Electrophoresis

  4. Infection by bacteriophage

Show answer
Correct Option: C
Explanation:

There are special techniques for the introduction of recombinant DNA into host cells. Microinjection, biolistics, infection by disarmed pathogens like Agrobacterium or bacteriophage are examples of such techniques. 

While electrophoresis is used for the separation of various DNA segments based on their length. 
So, the correct option is '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

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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.