Biology MCQs with Answers and Explanations

Which term describes genes that are located on the same chromosome and inherited together more often than by chance?

A. Linked genes
B. Epistatic genes
C. Polygenic genes
D. Independent genes

Explanation:
Linked genes are near each other on the same chromosome. They tend to be inherited together, and their recombination frequency is less than 50%.

Which of the following best describes polygenic inheritance?

A. One gene affects multiple traits (e.g., pleiotropy)
B. Many genes contribute to one trait (e.g., skin color)
C. A trait determined by genes only on the X chromosome
D. Inheritance of mitochondrial DNA

Explanation:
Polygenic inheritance means multiple genes (often with additive effects) determine a single phenotype, such as height or skin color, producing continuous variation.

Which plasmid-based technique is used to enrich and detect low-abundance mRNAs by reverse transcription into cDNA?

A. RFLP analysis
B. Northern blotting
C. RT-PCR (reverse-transcription PCR)
D. Affinity chromatography

Explanation:
RT-PCR involves reverse-transcribing RNA to cDNA and then amplifying specific sequences by PCR. It is very sensitive for detecting low-abundance transcripts.

Which assay would you use to detect and quantify a specific DNA sequence in a sample?

A. ELISA
B. Southern blot
C. Western blot
D. Gram staining

Explanation:
A Southern blot uses a DNA probe to hybridize with a specific DNA sequence immobilized on a membrane, allowing detection of that sequence in the sample.

In tissue engineering, a scaffold material must typically be:

A. Non-biodegradable only
B. Biocompatible and biodegradable
C. Made of metal only
D. Radioactive

Explanation:
Tissue scaffolds are usually biocompatible (non-toxic, no immune response) and biodegradable so that they eventually degrade as new tissue forms in the scaffold’s place.

Somatic cell nuclear transfer (SCNT) for reproductive cloning involves:

A. Injecting somatic cell DNA into a fertilized egg with its nucleus intact
B. Fusing a diploid somatic cell with an enucleated egg cell
C. Using only oocyte mitochondria from a donor
D. Cloning via binary fission

Explanation:
SCNT (as in cloning Dolly the sheep) entails transferring the nucleus of an adult somatic cell into an enucleated oocyte, and then stimulating the resulting cell to divide as an embryo.

Which of the following is NOT typically controlled during industrial fermentation in a bioreactor?

A. Temperature
B. pH
C. Oxygen concentration
D. DNA sequence of the microorganism

Explanation:
A, B, and C (temperature, pH, oxygen) are critical parameters controlled in fermentation. The chosen strain fixes the DNA sequence and is not a controlled parameter during the run.

Which chromatography technique separates proteins primarily based on size using a gel matrix?

A. Ion-exchange chromatography
B. Gel filtration (size-exclusion) chromatography
C. Affinity chromatography
D. Reverse-phase chromatography

Explanation:
Gel filtration chromatography (size-exclusion) separates proteins by size: larger molecules elute first because they enter fewer pores in the matrix, while smaller molecules elute later.

In flow cytometry, cells are labeled with fluorescent antibodies and passed in a stream through a laser. This technique primarily measures:

A. Cell size and internal complexity
B. DNA sequence variants
C. Protein structure by X-ray diffraction
D. Glycolytic activity

Explanation:
Flow cytometry measures light scattering (size and granularity) and fluorescence from labeled markers, allowing rapid analysis of cell populations (size, complexity, marker expression).

Monoclonal antibodies differ from polyclonal antibodies in that monoclonals:

A. Are produced by multiple B cell clones
B. Recognize multiple epitopes on the same antigen
C. Are derived from a single B cell clone and recognize a single epitope
D. Are less specific than polyclonals

Explanation:
Monoclonal antibodies come from one B-cell clone, so they are identical and recognize one epitope. Polyclonal antibodies are produced by many B cells and recognize multiple epitopes on the antigen.