The 'pUC19' plasmid is a widely used cloning vector. A key feature of pUC19 that facilitates the selection of recombinant clones is the presence of: MCQ with Answer and Explanation
The 'pUC19' plasmid is a widely used cloning vector. A key feature of pUC19 that facilitates the selection of recombinant clones is the presence of:
A. The lacZ gene for alpha-complementation (blue-white screening)
B. Genes for nitrogen fixation
C. The rop gene for replication control
D. Multiple origins of replication
Answer: Option A
Solution (By JKExamLibrary)
pUC19 is a small, high-copy-number cloning vector. A crucial feature for selecting recombinant clones is the presence of the lacZ' gene, which codes for the alpha-peptide of beta-galactosidase. The multiple cloning site (MCS) is located within this lacZ' gene. When foreign DNA is inserted into the MCS, it disrupts the lacZ' gene (insertional inactivation). On media containing X-gal and IPTG, colonies with empty vectors turn blue, while colonies with recombinant plasmids (disrupted lacZ') remain white, allowing easy visual selection.
Consider statements about vitamins: 1. Vitamin D is synthesized in the skin upon sunlight exposure. 2. Vitamin B12 is the only vitamin containing a metal ion. 3. Vitamin A is essential for blood clotting. Which are correct?
Explanation:
Vitamin D3 (cholecalciferol) is synthesized in the epidermis of the skin when 7-dehydrocholesterol is exposed to ultraviolet B (UVB) radiation from sunlight. Vitamin B12 (cobalamin) is unique among vitamins as it contains the metal ion cobalt in its structure. Vitamin K, not Vitamin A, is essential for the synthesis of blood clotting factors. Vitamin A is crucial for vision and immunity. Thus, statements 1 and 2 are correct.
Explanation:
Vitamin B₁₂ (cobalamin) is required for DNA synthesis and RBC maturation. Deficiency causes pernicious anemia. It also maintains myelin sheath.
Explanation:
Centrioles are cylindrical structures composed of nine evenly spaced peripheral fibrils of tubulin, arranged in a 9+0 pattern. Each fibril is a triplet of microtubules. The central part is non-branched and lacks microtubules. Centrioles are involved in forming the spindle apparatus in animal cells and basal bodies of cilia and flagella.
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