All Free Biology MCQs with Answers

• A. Genetic information
• B. Yolk
• C. Cytoplasm
• D. Organelles

Explanation: Gametes are haploid and have a half set of chromosomes. During fertilization egg and sperm with an equal number of chromosomes fuse to form a zygote, and contribute equal genetic information for the development of the baby.

• A. DNA polymerase I
• B. DNA polymerase III
• C. DNA polymerase II
• D. DNA Ligase

Explanation: DNA polymerase III is the main replicating enzyme. It has two subunits. Both leading and lagging strands are constructed by DNA polymerase III. Each Okazaki fragment is synthesised by DNA polymerase III in a 5' → 3' direction.

• A. Towards replication fork
• B. Towards another DNA molecule
• C. Away from replication fork
• D. Towards other strand of DNA molecule

Explanation: Overall, the process of replication is always towards the replication fork. DNA polymerase III can add nucleotides only at 3 ends of the primer, and to construct the okazaki fragment, DNA polymerase IIl jumps away from the replication fork. In order to construct another Okazaki fragment on the lagging strand, DNA polymerase III jumps away from the replication fork. DNA polymerase III cannot synthesise DNA in the 5' to 3' direction continuously on the lagging strand, as it can on the leading strand. Instead, it synthesises short segments of DNA in the 5' to 3' direction, away from the replication fork.

• A. Two heavy strands having N15
• B. Two light Strands having N14
• C. Hybrid possessing heavy and light each
• D. Not specified

Explanation: In the Meselson-Stahl experiment, after the first round of DNA replication, each daughter DNA duplex consists of a hybrid DNA molecule possessing both heavy and light strands. When this hybrid duplex is replicated during the second round of DNA replication, it contributes one heavy strand to form another hybrid duplex and one light strand to form a light duplex.

• A. Pentose sugars
• B. Bonding
• C. Phosphate groups
• D. Bases

Explanation: In Meselson-Stahl's experiment, radioactive isotopes of nitrogen were used. This radioactive nitrogen became incorporated in the nitrogenous bases and aided in the separation of variable DNA strands in Meselson-Stahl's experiments. Replication of DNA is a process where stability and consistency of genetic information are maintained generation after generation or from parents to offspring. This stability and high degree of accuracy are provided by hydrogen bonding between base pairs of old and newly formed DNA strands.

• A. Parent strand
• B. Lagging strand
• C. Leading strand
• D. None of these

Explanation: The leading strand is the strand of nascent DNA which is synthesised in the same direction as the growing replication fork. This sort of DNA replication is continuous.

• A. 10-20 nucleotides
• B. 1000-2000 nucleotides
• C. 100-200 nucleotide
• D. Variable

Explanation: Okazaki fragments are DNA nucleotides sequence synthesized by DNA polymerase III during the replication of the lagging strand variable length. In the case of prokaryotes, these fragments are 1000-2000 nucleotides long and in the case of eukaryotes, these fragments are 100-200 nucleotides long.

• A. DNA proof-reading
• B. DNA repair
• C. Unwinding
• D. Annealing

Explanation: DNA polymerase enzyme has three types: DNA polymerase-I is involved in proof-reading activities. DNA polymerase-II is involved in DNA repair. DNA polymerase-III is the main enzyme of replication.

• A. Codon
• B. Triplet code
• C. Anticodon
• D. Gene

Explanation: Genes are fundamental units of heredity, made of DNA, that carry instructions for building and operating living organisms, determining traits like eye colour by coding for specific proteins or functional RNA. Located on chromosomes within cells, humans have around 20,000 protein-coding genes, with most individuals inheriting two copies of each gene, one from each parent, influencing unique characteristics and bodily functions.

• A. mRNA
• B. rRNA
• C. tRNA
• D. DNA

Explanation: During translation, the site where polypeptides (proteins) are assembled is provided by rRNA (ribosomal RNA). Ribosomes, which consist of both ribosomal RNA (rRNA) and protein components, serve as the cellular machinery for protein synthesis. The rRNA molecules within the ribosome catalyse the formation of peptide bonds between amino acids, allowing for the assembly of a polypeptide chain based on the information carried by the mRNA (messenger RNA) and guided by tRNA (transfer RNA) molecules. mRNA carries the genetic code from the DNA to the ribosome, while tRNA molecules bring specific amino acids to the ribosome. However, it is the rRNA that plays a central role in the actual process of peptide bond formation and protein synthesis.