What is the PAM (Protospacer Adjacent Motif) sequence requirement in Streptococcus pyogenes CRISPR-Cas9?
Answer: B
S. pyogenes Cas9 recognizes the PAM sequence NGG (usually GG) immediately downstream of the target sequence, which is essential for proper target site recognition.
Q.42Medium
In transcription factor-based gene regulation, which domain is responsible for DNA binding?
Answer: B
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.
Q.43Medium
Which of the following is an example of a selectable marker gene used in genetic engineering?
Answer: A
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.
Q.44Medium
In gene therapy, what is the primary advantage of using adeno-associated virus (AAV) as a vector?
Answer: B
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).
Q.45Medium
What is the significance of the TATA box in eukaryotic gene expression?
Answer: B
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.
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Q.46Medium
Which chromosomal engineering technique is used to determine the order and orientation of genes on a chromosome?
Answer: B
Physical and chromosomal mapping techniques such as FISH (Fluorescence In Situ Hybridization), optical mapping, and chromosome walking determine gene order and positions on chromosomes.
Q.47Medium
In the context of RNA interference (RNAi), what is the role of the RISC complex?
Answer: B
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.
Q.48Medium
A biotechnology company in India has developed a transgenic crop that produces its own Bt toxin for pest resistance. Which of the following best explains the mechanism by which this toxin controls insect pests?
Answer: B
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.
Q.49Medium
In CRISPR-Cas9 gene editing technology, what is the specific role of the single guide RNA (sgRNA)?
Answer: B
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.
Q.50Medium
During the development of a genetically modified organism (GMO), scientists use selectable marker genes. If an antibiotic resistance gene is used as a marker, which scenario would indicate successful transformation?
Answer: A
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.
