All Free Biology MCQs with Answers

2251. The sequence of 3 bases on tRNA which is complementary to condon of mRNA is called____________?

• A. Gene
• B. Anticodon
• C. Code
• D. Codon

Explanation: The anticodon is a three-base sequence on tRNA that pairs complementarily with a codon on mRNA during translation. This pairing positions the tRNA's attached amino acid correctly for protein synthesis. Students may choose codon because both are three-base sequences, but a codon is found on mRNA whereas an anticodon is found on tRNA.

2252. Which statement correctly describes the transcription of DNA?

• A. It produces another DNA molecule
• B. It produces mRNA
• C. It is a semi conservation process
• D. It occurs at surface of ribosomes

Explanation: Transcription uses one DNA strand as a template to synthesize a complementary RNA molecule, commonly mRNA for a protein-coding gene. It occurs in the nucleus of eukaryotic cells, whereas ribosomes use mRNA during translation in the cytoplasm. Students may choose semi-conservative replication because DNA is involved, but semi-conservative copying produces DNA, not mRNA.

2253. How many carbon atoms are required to form a furan ring (ribofuranose)_____________?

• A. 3
• B. 4
• C. 5
• D. 2Health

Explanation: A furanose ring is a five-membered ring containing four carbon atoms and one oxygen atom, so ribofuranose has 4 ring carbons. The likely mistake is choosing 5 by counting all ring atoms and forgetting that one of them is oxygen.

2254. Which of the following statement is incorrect about RNA_________________?

• A. The pentose sugar in it is Ribose.
• B. It contains Adenine Guanine Thymine and Cytosine
• C. It is present in the nucleoli
• D. It may be folded back on itself to give double helical characteristics.

Explanation: RNA contains ribose sugar and the bases adenine, guanine, cytosine and uracil, not thymine. It is found in the nucleolus as ribosomal RNA and can fold back on itself to form short double-helical regions through complementary base pairing. Students may choose c if they think RNA occurs only in the cytoplasm, but several types of RNA are present in the nucleus and nucleolus.

2255. A group of ribosomes attached to mRNA is known as___________?

• A. Polymer
• B. Polypeptide
• C. Polysomes
• D. Monomer

Explanation: A polysome, or polyribosome, is a group of ribosomes simultaneously attached to one mRNA molecule, allowing several copies of a polypeptide to be made at once. Students may choose polypeptide because ribosomes produce polypeptides, but that term names the product, not the ribosome cluster.

2256. Polysome is formed during __________ process?

• A. Transcription
• B. Secretion
• C. Translation
• D. Division

Explanation: A polysome, or polyribosome, forms when several ribosomes simultaneously translate one mRNA molecule, allowing many copies of a protein to be produced. Students may choose transcription because mRNA is involved, but transcription makes RNA from DNA whereas translation reads mRNA to make protein.

2257. The liquid that escapes during defrosting frozen meat contains _____ bacteria?

• A. Campylobacter
• B. Nitrobacter
• C. Azobacter
• D. Salmonella

Explanation: Defrosting meat can release contaminated fluid, and Salmonella may be present and spread to other foods or surfaces. Campylobacter can also contaminate poultry, so students may choose it because it is another important foodborne pathogen, but the expected textbook association here is Salmonella.

2258. The study of interaction of antigen and antibodies in blood is ___________?

• A. etiology
• B. serology
• C. ecology
• D. histology

Explanation: Serology is the study of blood serum, especially the antibodies and antigens found in it and their reactions. Students may choose histology because it also ends in '-logy', but histology deals with tissues rather than immune reactions in serum. Etiology concerns the causes of disease, while ecology concerns organism-environment interactions.

2259. On wound __________ fight foreign particles, like bacteria?

• A. White Blood cells
• B. Red Blood Cells
• C. Platelets
• D. Plasma

Explanation: White blood cells defend a wound by recognizing, engulfing, or destroying invading bacteria and by coordinating immune responses. Students may choose platelets because they act at wounds, but platelets mainly form clots and do not provide the principal cellular defence against bacteria.

2260. Which of the following diseases induce immunity?

• A. Smallpox
• B. Jaundice
• C. Diabetes
• D. None of these

Explanation: A person who recovers from smallpox develops specific immune memory against the smallpox virus, although vaccination is the safer way to acquire protection. Diabetes does not normally produce protective immunity, so students may choose it simply because it is a major disease rather than an infectious disease that stimulates immune memory.