Question

Pick the correct statements :
A. Restriction enzymes produce sticky or blunt ends.
B. DNA ligase forms disulfide bonds.
C. All plasmids act as cloning vectors.
D. Recombinant DNA can be expressed in a suitable host cell.
E. YACs are used for preparing human genome libraries.
Choose the correct answer from the options given below :

• A. \(B, C, D\) only
• B. \(A, B\) only
• C. \(A, D, E\) only
• D. \(C, D\) only

Hint:

Remember:
• Restriction enzymes \(\rightarrow\) Sticky or blunt ends
• DNA ligase \(\rightarrow\) Forms phosphodiester bonds
• YACs \(\rightarrow\) Large DNA cloning vectors \[ \text{YAC} = \text{Yeast Artificial Chromosome} \]

Answer 1

The Correct Option is C

Concept: Recombinant DNA technology involves:
• Cutting DNA with restriction enzymes
• Joining DNA fragments using ligases
• Cloning DNA into vectors
• Expression of genes in host organisms Different vectors such as plasmids and YACs are used for cloning DNA fragments.

Step 1: Evaluating statement A. Statement A: \[ \text{Restriction enzymes produce sticky or blunt ends} \] This is correct. Restriction endonucleases may generate:
• Sticky (cohesive) ends
• Blunt ends depending on their cleavage pattern. Thus: \[ \boxed{A \text{ is correct}} \]

Step 2: Evaluating statement B. Statement B: \[ \text{DNA ligase forms disulfide bonds} \] This is incorrect. DNA ligase forms: \[ \text{Phosphodiester bonds} \] between adjacent nucleotides in DNA strands. Disulfide bonds occur in proteins between cysteine residues. Thus: \[ \boxed{B \text{ is incorrect}} \]

Step 3: Evaluating statement C. Statement C: \[ \text{All plasmids act as cloning vectors} \] This is incorrect. Only specially engineered plasmids possessing features such as:
• Origin of replication
• Selectable markers
• Multiple cloning sites are used as cloning vectors. Thus: \[ \boxed{C \text{ is incorrect}} \]

Step 4: Evaluating statement D. Statement D: \[ \text{Recombinant DNA can be expressed in suitable host cells} \] This is correct. Examples of hosts include:
• E.coli
• Yeast
• Mammalian cells Thus: \[ \boxed{D \text{ is correct}} \]

Step 5: Evaluating statement E. Statement E: \[ \text{YACs are used for preparing human genome libraries} \] This is correct. YACs (Yeast Artificial Chromosomes) can carry very large DNA inserts and were widely used in: \[ \text{Human Genome Project} \] Thus: \[ \boxed{E \text{ is correct}} \] Therefore, the correct statements are: \[ \boxed{A, D, E} \] Hence, the correct answer is: \[ \boxed{(C)\ A, D, E \text{ only}} \]