What is the optimal annealing temperature range for most PCR reactions?
Answer: A
The annealing temperature typically ranges from 45-65°C and depends on the Tm (melting temperature) of the primers used. This temperature allows primers to bind specifically to target DNA.
Q.42Easy
Which thermostable DNA polymerase is most commonly used in standard PCR?
Answer: A
Taq polymerase, isolated from Thermus aquaticus, is the most widely used enzyme in PCR due to its heat stability and ability to synthesize DNA at high temperatures.
Q.43Easy
In a typical PCR cycle, DNA denaturation occurs at approximately which temperature?
Answer: B
DNA denaturation in PCR occurs at 94-95°C (or sometimes 98°C), where hydrogen bonds between DNA strands are broken, separating the double helix into single strands.
Q.44Easy
What is the primary function of dNTPs in PCR?
Answer: B
dNTPs (deoxynucleotide triphosphates) are the precursor molecules that DNA polymerase incorporates into the growing DNA strand during the extension phase of PCR.
Q.45Easy
Which enzyme is primarily responsible for extending DNA strands during the elongation phase of PCR?
Answer: A
Taq polymerase, derived from Thermus aquaticus, is a heat-stable DNA polymerase that extends primers during PCR elongation at 72°C.
Advertisement
Q.46Easy
In a standard PCR cycle, at what temperature is the DNA double helix typically denatured?
Answer: C
Denaturation occurs at 94-95°C where hydrogen bonds between complementary DNA strands break, separating double-stranded DNA into single strands.
Q.47Easy
What is the theoretical maximum amplification of a DNA segment after 30 PCR cycles?
Answer: B
Each PCR cycle doubles the DNA amount (exponential amplification). After 30 cycles, theoretical amplification = 2^30 ≈ 10^9 fold increase.
Q.48Easy
What is the primary role of dNTPs (deoxynucleotide triphosphates) in the PCR reaction mixture?
Answer: A
dNTPs (dATP, dGTP, dCTP, dTTP) are incorporated into the growing DNA strand by Taq polymerase via phosphodiester bond formation.
Q.49Easy
Which of the following is the most commonly used culture medium for animal cell culture in laboratories?
Answer: A
DMEM is the most widely used culture medium for mammalian/animal cell culture due to its balanced nutrient composition. LB broth is for bacteria, PDA for fungi, and Czapek Dox for fungi.
Q.50Easy
What is the primary purpose of using a laminar flow hood in cell culture?
Answer: B
Laminar flow hoods create unidirectional airflow through HEPA filters, maintaining a sterile environment and preventing microbial contamination during cell culture operations.
Q.51Easy
Which of the following characteristics is essential for continuous cell lines?
Answer: B
Continuous cell lines (like HeLa, CHO) have unlimited replicative potential due to telomerase activation or genetic modifications, allowing indefinite division unlike primary cultures.
Q.52Easy
What is the normal pH range required for optimal mammalian cell culture?
Answer: B
Mammalian cells require a pH of 7.2-7.4 (physiological pH) for optimal growth. This is maintained using buffers like bicarbonate or HEPES in culture media.
Q.53Easy
Which growth factor is primarily responsible for promoting cell proliferation in mammalian cell culture media?
Answer: A
EGF is a primary mitogenic growth factor that stimulates cell proliferation. While other factors support cell survival, EGF is specifically responsible for promoting cell division in mammalian cultures.
Q.54Easy
What is the primary purpose of using serum-free media (SFM) in industrial cell culture?
Answer: B
Serum-free media reduce lot-to-lot variability of serum batches, improve product purity, and simplify downstream purification processes, making them essential for pharmaceutical production.
Q.55Easy
Which of the following cell lines is commonly used for monoclonal antibody production?
Answer: B
Myeloma cell lines (NSO or SP02) are immortal cells used to create hybridomas through fusion with B lymphocytes for monoclonal antibody production.
Q.56Easy
The doubling time of mammalian cells cultured in vitro typically ranges between:
Answer: B
Most mammalian cell lines have doubling times of 12-24 hours under optimal culture conditions. Bacterial doubling times are much shorter (2-4 hours).
Q.57Easy
Which disinfectant is most commonly used for sterilizing bioreactor surfaces and cell culture equipment?
Answer: A
70% ethanol is the standard disinfectant for cell culture work due to its effectiveness against most microorganisms and minimal residual toxicity to cells.
Q.58Easy
Which growth phase of bacterial culture is characterized by maximum specific growth rate and exponential increase in cell number?
Answer: B
Log phase (logarithmic/exponential phase) is when cells divide at maximum rate with doubling time remaining constant. This is the phase of active cell proliferation.
Q.59Easy
What is the optimal pH range for mammalian cell culture?
Answer: B
Mammalian cells require slightly alkaline to neutral pH (7.2-7.4) for optimal growth. pH is maintained using buffers like bicarbonate or HEPES.
Q.60Easy
Which of the following is NOT a component of basal culture media?
Answer: C
Basal media contain amino acids, vitamins, inorganic salts, and carbohydrates. Monoclonal antibodies are added supplements, not basal media components.
