All Free Biology MCQs with Answers

• A. Nitrogenous bases
• B. Ribose Sugars
• C. Deoxyribose Sugars
• D. Phosphate groups

Explanation: Deoxyribose sugars are not part of RNA, rather ribose sugars are part of RNA. Deoxyribose sugars are found in DNA molecules.

• A. Option A: alanine - GCA = CGT, arginine - CGA = GCT, lysine - AAG = TTC, phenylalanine - UUU = AAA
• B. Option B: alanine - GCU = CGA, arginine - AGG = TCC, lysine - AAA = TTT, phenylalanine - UUU = AAG
• C. Option C: alanine - GCC = GGC, arginine - CGG = GCC, lysine - AAG = TTC, phenylalanine - UUU = AAA
• D. Option D: alanine - GCA = TGT, arginine - CGA = GCT, lysine - AAG = TTC, phenylalanine - UUU = AAA
• E. Option E: alanine - GCU = CGA, arginine - CGG = GCC, lysine - AAA = TTT, phenylalanine - UUC = AAG

Explanation: mRNA is complementary to the DNA template strand (and replaces T with U).

• A. Hereditary
• B. Secretory
• C. Power house
• D. Food synthesis

Explanation: Chromosomes are thread-like structures made up of DNA and proteins, and are present in the nucleus of eukaryotic cells.

• A. Epistasis
• B. Gene linkage
• C. Crossing over
• D. Pleiotropy

Explanation: Gene linkage is a physical relationship of genes present on the same chromosome, which results in the tendency of the genes to be…

• A. TAG
• B. AUG
• C. UAG
• D. AAA

Explanation: UAG is one of the three stop codons, also known as termination codons, in the genetic code. The other two stop codons are UAA and UGA.

• A. The primary structure is preserved, while the secondary structure is altered.
• B. The secondary structure is preserved, while the primary structure is altered.
• C. Both the primary and secondary structures remain unchanged.
• D. Both the primary and secondary structures are disrupted.

Explanation: In semi-conservative replication, the DNA molecule separates into two strands, each serving as a template for a new complementary strand.

• A. It increases the frequency of an allele
• B. It is the same as disruptive selection
• C. It increases genetic diversity
• D. It removes variation from the population

Explanation: Purifying selection, also known as negative selection, is a type of natural selection that acts to eliminate harmful or deleterious…

• A. Mendel
• B. Boveri
• C. Sutton
• D. Fleming

Explanation: The term was discovered by the German scientist Heinrich Wilhelm Waldeyer in 1888, it referred to chromatin at the time which was later…

• A. PKU
• B. Alkaptonuria
• C. Anuria
• D. Dluria

Explanation: Phenylketonuria (PKU) is the correct answer as it is a genetic disorder caused by a deficiency of the enzyme phenylalanine hydroxylase…

• A. Both are due to a quantitative defect in globin chain synthesis
• B. Thalassemia is due to less synthesis of globin molecules
• C. Sickle cell anemia is due to a quantitative problem of globin molecules
• D. Both are due to a qualitative defect in globin chain synthesis

Explanation: Sickle cell anemia is caused by a point mutation at the 6th position of the beta-globin chain, where glutamic acid is replaced by valine…

• A. DNA replicates by semi-conservative replication
• B. Cyanobacteria were responsible for the oxygenation of the atmosphere
• C. The early atmosphere was composed of ammonia and methane
• D. Organic molecules can arise from inorganic precursors

Explanation: The Urey-Miller experiment was a groundbreaking study that demonstrated that organic molecules, like amino acids, could be formed from…

• A. Does not code for proteins and is the same in all members of the population
• B. Codes for enzymes needed for DNA replication
• C. Codes for proteins needed in cell cycle
• D. Shows a high degree of polymorphism in the population and also the same degree of polymorphism in an individual, which is heritable from parents to children

Explanation: Satellite DNA is that part of repetitive DNA that has long repetitive nucleotide sequences in tandem that form a separate fraction on…

• A. Formation of formyl-­met­t-RNA
• B. Binding of 30S subunit of ribosome with mRNA
• C. Association of 30S mRNA with formyl­-mett-RNA
• D. Association of 50S subunit of ribosome with initiation complex.

Explanation: During translation initiation in prokaryotes, a GTP molecule is needed in the association of 30S mRNA with formyl-mett-RNA.This is because…

• A. 'I' gene
• B. Promoter gene
• C. b­-galactosidase
• D. Lactose

Explanation: Lac operon in E. coli is induced by b­-galactosidase- an enzyme meant for the hydrolysis of lactose in glucose and galactose.

• A. Serine and isoleucine
• B. Cysteine and valine
• C. Tyrosine and tryptophan
• D. Phenylalanine and methinonine

Explanation: Khorana synthesized a chain of alternate nucleotides GUGUGUGUGU. He found that it stimulated the synthesis of a peptide having alternate…

• A. Endosome
• B. Nucleosome
• C. Mesosome
• D. Centromere

Explanation: An octamer of 4 histones complexed with DNA forms a nucleosome. The association of histones with DNA is very characteristic.

• A. 10 nucleotides/ second
• B. 1000 nucleotides/ second
• C. 100 nucleotides/ second
• D. 10000 nucleotides/ second

Explanation: DNA polymerase III is the main enzyme involved in prokaryotic DNA replication.

• A. Condensation
• B. Polymerization
• C. Replication
• D. Transcription

Explanation: DNA replication is the process by which a ds-DNA molecule is copied to produce two daughter DNA molecules.

• A. Whom could they choose but the man who had worked for it all those years?
• B. To whom could they choose but the man who had work for it all those years?
• C. Which could they choose but the man who had work for it all those years?
• D. Whose could they choose but the man who had work for it all those years?

Explanation: This option is correct. "Whom" is used correctly here as the object of the verb "choose."

• A. Globular proteins
• B. Glycoproteins
• C. Fibrous proteins
• D. Glycolipids

Explanation: Antibodies are globular proteins that play a key role in the immune system by binding to antigens.