Biology MCQs with Answers and Explanations

Human insulin production by recombinant DNA technology was first achieved in:

A. Yeast cells
B. Bacterial cells
C. Mammalian cells
D. Plant cells

Explanation:
The first human protein successfully produced by genetic engineering was insulin, expressed in genetically modified Escherichia coli bacteria.

Pluripotent stem cells are characterized by their ability to:

A. Differentiate into all cell types, including extraembryonic membranes
B. Differentiate into any cell type of the body (but not extraembryonic tissues)
C. Self-renew indefinitely but only become one cell type
D. Be harvested from adult muscle tissue

Explanation:
Pluripotent stem cells (like embryonic stem cells) can form any body cell type (endoderm, mesoderm, ectoderm) but cannot form an entire organism (unlike totipotent zygotes).

Fluorescence in situ hybridization (FISH) is a technique used to:

A. Fragment DNA into smaller pieces
B. Visualize specific DNA or RNA sequences in cells or chromosomes using fluorescent probes
C. Measure protein concentration in solution
D. Separate DNA by size

Explanation:
FISH uses fluorescently labeled probes that hybridize to specific DNA sequences on chromosomes or cells, allowing localization under a fluorescence microscope.

In Western blotting, proteins are typically detected using:

A. DNA probes
B. RNA probes
C. Enzyme-linked antibodies
D. Radioactive amino acids

Explanation:
Western blot uses antibodies (often enzyme-linked) that bind specific proteins on the membrane, allowing visualization via a colorimetric or chemiluminescent reaction.

In Northern blotting, the labeled probe hybridizes to:

A. DNA immobilized on a membrane
B. RNA immobilized on a membrane
C. Protein immobilized on a membrane
D. Any membrane-bound molecules

Explanation:
A Northern blot is used to detect RNA. A labeled DNA or RNA probe hybridizes to the target RNA on the membrane.

In Southern blotting, what type of probe is used to detect specific DNA sequences?

A. DNA probe labeled with a reporter
B. RNA probe labeled with a reporter
C. Protein probe labeled with antibody
D. Carbohydrate probe

Explanation:
Southern blot uses a labeled single-stranded DNA (or RNA) probe complementary to the target DNA sequence, hybridizing to it on the membrane.

The technique for producing monoclonal antibodies involves fusing a specific antibody-producing B cell with a myeloma cell (a cancer cell). This hybrid cell line is called a:

A. Bacteriophage
B. Hybridoma
C. Plasmid
D. Complement

Explanation:
A hybridoma results from fusing a single B lymphocyte (which produces one antibody) with a myeloma cell, creating an immortal cell line that produces identical (monoclonal) antibodies.

SDS-PAGE separates proteins primarily based on:

A. Charge only
B. Size (molecular weight)
C. Hydrophobicity
D. Isoelectric point

Explanation:
SDS denatures proteins and coats them with a negative charge that is proportional to their length. In SDS-PAGE, proteins are separated by size; smaller proteins migrate faster.

During agarose gel electrophoresis of DNA, in which direction do DNA fragments migrate?

A. Toward the cathode (negative electrode)
B. Toward the anode (positive electrode)
C. DNA does not migrate in agarose
D. Toward the North Pole

Explanation:
DNA has a negative charge (due to phosphate groups) and migrates toward the positively charged electrode (anode) when an electric field is applied.

In a cloning vector, what is the purpose of including an antibiotic resistance gene?

A. To replicate the plasmid in host cells
B. As a selectable marker to identify transformed cells
C. To transcribe the cloned gene at high levels
D. To initiate DNA replication

Explanation:
The antibiotic resistance gene allows selection: only bacteria that have taken up the plasmid (and express resistance) will grow on antibiotic-containing media.