Biotechnology - MCQ Practice Questions

Gene targeting uses homologous recombination to introduce specific changes at exact genomic locations, while CRISPR, TALENs, and ZFNs create double-strand breaks that are repaired by non-homologous end joining.

S. pyogenes Cas9 recognizes the PAM sequence NGG (usually GG) immediately downstream of the target sequence, which is essential for proper target site recognition.

The Ti (Tumor-inducing) plasmid naturally transfers a portion of its DNA (T-DNA) into plant cells. Scientists use this as a natural vector to introduce desired genes into plants.

Bt Cotton was approved by the Indian government in 2002 and became the first genetically modified crop to be commercially cultivated in India, significantly impacting cotton production.

Bt stands for Bacillus thuringiensis, a soil bacterium that produces Cry proteins toxic to lepidopteran insects. The Cry gene is inserted into cotton plants to confer insect resistance.

The DNA-binding domain (DBD) of transcription factors contains specific structures (zinc fingers, helix-turn-helix, leucine zippers) that recognize and bind to specific DNA sequences.

Selectable marker genes confer resistance to antibiotics or toxins, allowing researchers to identify and select transformed cells. Antibiotic resistance genes are the most common examples.

AAVs are small viruses with low immunogenicity, can transduce non-dividing cells, and are relatively safe for clinical use. However, they have limited packaging capacity (~4.7 kb).

The TATA box is a promoter element located ~25-30 bp upstream of the transcription start site. It binds transcription factor IID (TFIID) and directs RNA polymerase II to the correct position.

Physical and chromosomal mapping techniques such as FISH (Fluorescence In Situ Hybridization), optical mapping, and chromosome walking determine gene order and positions on chromosomes.

The RNA-Induced Silencing Complex (RISC) uses small RNA molecules (siRNA or miRNA) as guides to recognize and degrade complementary mRNA sequences, leading to gene silencing.

The GEAC, operating under the MoEFCC, is responsible for appraising large-scale field trials and commercial release of genetically modified organisms in India.

TALENs consist of a modular DNA-binding domain (which recognizes specific sequences) fused to the FokI nuclease domain, allowing precise DNA cleavage at target sites.

Whole-genome sequencing provides unbiased coverage of the entire genome, allowing discovery of unexpected mutations, copy number variations, and structural rearrangements not detected by targeted approaches.

Homologous recombination has very low frequency in mammalian cells compared to yeast, requiring enrichment strategies and selection markers. This limitation has been overcome by CRISPR technology.

E. coli is the primary organism used for recombinant insulin production due to its well-characterized genetics, rapid growth, and ability to produce high levels of recombinant proteins.

Restriction endonucleases (restriction enzymes) recognize and cut DNA at specific palindromic sequences, forming sticky or blunt ends. DNA polymerase synthesizes DNA, helicase unwinds DNA, and ligase joins DNA strands.

Bt toxin (Cry proteins) forms pores in the alkaline midgut of target insects, causing cell lysis and disruption of the intestinal epithelium. This is specific to lepidopteran, coleopteran, and dipteran insects with appropriate pH and protease conditions.

The sgRNA contains a CRISPR RNA (crRNA) and trans-activating CRISPR RNA (tracrRNA) combined into a single molecule. It guides the Cas9 nuclease to the target DNA sequence through Watson-Crick base pairing, ensuring specificity of the cut.

Selectable marker genes confer resistance to specific antibiotics or toxins. When the transformation vector carries an antibiotic resistance gene, only cells that successfully incorporated the vector will express the resistance gene and survive on antibiotic-containing media. Non-transformed cells lack this gene and are eliminated.