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

Question

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. Multiple origins of replication

B. The lacZ gene for alpha-complementation (blue-white screening)

C. The rop gene for replication control

D. Genes for nitrogen fixation

Answer: Option B

Solution (By JKSSB Mock Tests)

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.

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Question #1

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The long, cylindrical, highly specialized part of a neuron that conducts nerve impulses away from the cell body is the:

A. Dendrite

B. Soma

C. Axon

D. Myelin sheath

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Correct Answer: Option C

Explanation:
A neuron consists of a cell body (soma), dendrites, and an axon. Dendrites are short, branched processes that receive impulses and conduct them towards the cell body. The axon is a long, single, cylindrical fiber that conducts nerve impulses away from the cell body to other neurons, muscles, or glands. The myelin sheath is an insulating layer around the axon.

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Question #2

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In a food chain, the first trophic level is always occupied by:

A. Decomposers

B. Carnivores

C. Herbivores

D. Producers (Green plants)

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Correct Answer: Option D

Explanation:
A food chain represents the flow of energy and nutrients. The first trophic level is always occupied by producers (autotrophs), primarily green plants and algae, which convert solar energy into chemical energy via photosynthesis. The second level is primary consumers (herbivores), the third is secondary consumers (carnivores), and so on.

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