Biotechnology - MCQ Practice Questions

Plasmids are small, circular DNA molecules found in bacteria that can replicate independently and serve as excellent vectors for genetic engineering in prokaryotes.

The guide RNA (gRNA) is complementary to the target DNA sequence and directs the Cas9 nuclease protein to the specific location where the DNA needs to be cut.

Antibiotic resistance genes (like ampicillin resistance) are frequently used as selectable markers to identify successfully transformed cells that have incorporated the recombinant plasmid.

The Protospacer Adjacent Motif (PAM) is a 2-6 nucleotide sequence immediately next to the target site that is essential for Cas9 to recognize and cleave the DNA.

PCR amplifies specific DNA segments exponentially in cycles of heating and cooling, creating millions of copies without requiring bacterial cells or cloning vectors.

Agrobacterium tumefaciens naturally transfers the T-DNA region from its Ti (Tumor-inducing) plasmid into plant cell chromosomes, making it an excellent biological vector for plant genetic engineering.

Homologous recombination uses regions of DNA sequence similarity (homologous arms) flanking the insert to direct accurate integration at specific chromosomal locations.

Most first-generation gene therapy approaches target somatic cells to avoid heritable genetic modifications and ethical concerns associated with germline therapy.

Viruses have naturally evolved sophisticated mechanisms to infiltrate cells and deliver their genetic material, making modified viral vectors efficient delivery systems for therapeutic genes.

Substantial equivalence is a regulatory concept suggesting that if a GM crop is compositionally and nutritionally similar to its conventional counterpart, it can be considered equally safe.

E. coli is the preferred expression host for many therapeutic proteins including insulin and growth factors due to its rapid growth, well-characterized genetics, and established fermentation technology.

Mosaicism occurs when CRISPR editing is performed early in development, resulting in some cells being edited while others retain the original genotype, creating a mixed population.

The GEAC, functioning under the MOEFCC, is the apex body responsible for appraisal and approval of proposals relating to release of GMOs and products into the environment.

RNAi uses small interfering RNAs (siRNAs) that guide the RNA-Induced Silencing Complex (RISC) to degrade specific target mRNAs, effectively silencing gene expression post-transcriptionally.

Pooled CRISPR screening uses large libraries of guide RNAs to simultaneously test thousands of genetic perturbations, allowing identification of genes associated with specific phenotypes through NGS readout.

Base editors convert one nucleotide to another without creating double-strand breaks, but optimizing specificity to edit only intended bases while avoiding unintended modifications remains a significant hurdle.

Prime editing fuses Cas9 nickase with reverse transcriptase, allowing creation of diverse genetic modifications from a single RNA template without creating double-strand breaks, offering superior precision and safety.

MboI produces sticky ends identical to EcoRI due to recognition of similar DNA sequences (GATC), making them compatible for ligation.

PAM sequence is essential for Cas9 recognition and binding. Without PAM (typically NGG in S. pyogenes), Cas9 cannot cleave the target DNA, ensuring site-specific editing.

Origin of replication (ori) is essential for autonomous replication of plasmids. Without it, the plasmid cannot replicate and will be lost during cell division.