A. The cutting of DNA is done by molecular scissors.
B. The DNA fragments separate according to their size in an agarose gel, upon electrophoresis.
C. The separated DNA fragments can be seen without staining when exposed to UV light.
D. The separated DNA fragments, when stained with ethidium bromide, can be seen in visible light.
Choose the correct answer from the options given below :
Understanding DNA Separation and Visualization Techniques
This question assesses knowledge of common molecular biology techniques used for DNA manipulation and observation.
Analyzing Statement A: DNA Cutting
Statement A claims that "molecular scissors" are used to cut DNA. This refers to restriction enzymes, which are proteins that cleave DNA molecules at specific recognition nucleotide sequences. They act like precise scissors for DNA. Therefore, statement A is considered correct in the context of molecular biology.
Analyzing Statement B: DNA Separation by Electrophoresis
Statement B states that DNA fragments separate based on size in an agarose gel during electrophoresis. This is the fundamental principle of agarose gel electrophoresis. DNA molecules carry a net negative charge due to their phosphate backbone. When an electric field is applied, DNA fragments migrate towards the positive electrode. The gel matrix acts as a sieve, impeding the movement of larger fragments more than smaller ones. Thus, smaller DNA fragments travel faster and further through the gel than larger fragments. Statement B is correct.
Analyzing Statement C: Visualization Without Staining
Statement C suggests that separated DNA fragments are visible without staining when exposed to UV light. DNA itself does not inherently fluoresce strongly enough to be seen under UV light. Specific stains, such as ethidium bromide, are required to intercalate into the DNA and fluoresce under UV illumination, making the DNA bands visible. Therefore, statement C is incorrect.
Analyzing Statement D: Visualization in Visible Light
Statement D proposes that DNA fragments stained with ethidium bromide can be seen in visible light. While ethidium bromide does fluoresce, this fluorescence is typically excited by ultraviolet (UV) light, not visible light. Specialized equipment emitting UV light is needed to visualize the stained DNA bands. Therefore, statement D is incorrect.
Conclusion on Correct Statements
Based on the analysis:
- Statement A is correct (Restriction enzymes act as molecular scissors).
- Statement B is correct (Electrophoresis separates DNA by size in agarose gel).
- Statement C is incorrect (Staining is required for UV visualization).
- Statement D is incorrect (Ethidium bromide visualization requires UV light, not visible light).
The correct statements are A and B.
Similar Questions
- Which of the following statements are not true regarding restriction endonucleases ?
A. They are called molecular scissors.
B. These are the enzymes responsible for restricting the growth of bacteriophages in E. coli.
C. They cut the DNA only at the centre of the palindromic sites.
D. They remove nucleotides only from the ends of DNA fragments.
E. They recognise specific palindromic base-pair sequences.
Choose the correct answer from the options given below : - Identify the correct sequence of steps in each cycle of Polymerase Chain Reaction :
- Insertion of a foreign DNA at BamHI site in an E. coli cloning vector pBR322 results in the loss of antibiotic resistance towards :
- Match List I with List II :
List I List II A. Genetically modified organism I. Agrobacterium tumefaciens B. Thermostable DNA polymerase II. Bt cotton C. Ti plasmid III. Thermus aquaticus D. pBR322 IV. Escherichia coli
Choose the correct answer from the options given below :
Important Questions from Biotechnology
- Which of the following statements are not true regarding restriction endonucleases ?
A. They are called molecular scissors.
B. These are the enzymes responsible for restricting the growth of bacteriophages in E. coli.
C. They cut the DNA only at the centre of the palindromic sites.
D. They remove nucleotides only from the ends of DNA fragments.
E. They recognise specific palindromic base-pair sequences.
Choose the correct answer from the options given below : - Identify the correct sequence of steps in each cycle of Polymerase Chain Reaction :
- Insertion of a foreign DNA at BamHI site in an E. coli cloning vector pBR322 results in the loss of antibiotic resistance towards :
- Match List I with List II :
List I List II A. Genetically modified organism I. Agrobacterium tumefaciens B. Thermostable DNA polymerase II. Bt cotton C. Ti plasmid III. Thermus aquaticus D. pBR322 IV. Escherichia coli
Choose the correct answer from the options given below :
