Q61. Which of the following vitamins acts as an antioxidant?
(a) Vitamin D
(b) Vitamin K
(c) Vitamin E
(d) Vitamin B6
Answer: (c) Vitamin E
Explanation: Vitamin E is a powerful antioxidant that protects cells from oxidative damage caused by free radicals.
Q62. The deficiency of folic acid during pregnancy can lead to:
(a) Neural tube defects
(b) Beriberi
(c) Rickets
(d) Night blindness
Answer: (a) Neural tube defects
Explanation: Folic acid (Vitamin B9) is crucial during early pregnancy for the development of the neural tube in the fetus. Its deficiency can result in neural tube defects like spina bifida.
Q63. Which of the following nitrogenous bases is present in RNA but not in DNA?
(a) Thymine
(b) Guanine
(c) Uracil
(d) Adenine
Answer: (c) Uracil
Explanation: In RNA, uracil replaces thymine as one of the pyrimidine bases, pairing with adenine during transcription.
Q64. DNA replication occurs during which phase of the cell cycle?
(a) G1 phase
(b) G2 phase
(c) S phase
(d) M phase
Answer: (c) S phase
Explanation: DNA replication occurs during the S phase (Synthesis phase) of the cell cycle, ensuring that each daughter cell receives a complete set of chromosomes.
Q65. Which enzyme is responsible for unwinding the DNA double helix during replication?
(a) DNA polymerase
(b) Helicase
(c) Ligase
(d) Primase
Answer: (b) Helicase
Explanation: Helicase unwinds the DNA double helix, creating replication forks where the DNA strands are separated to allow replication.
Q66. Which type of RNA serves as the template for protein synthesis?
(a) mRNA
(b) tRNA
(c) rRNA
(d) snRNA
Answer: (a) mRNA
Explanation: Messenger RNA (mRNA) carries the genetic information from DNA to the ribosome, where it serves as a template for protein synthesis.
Q67. The process of synthesizing a protein from mRNA is called:
(a) Replication
(b) Transcription
(c) Translation
(d) Mutation
Answer: (c) Translation
Explanation: Translation is the process in which the mRNA sequence is used by ribosomes to assemble amino acids into a polypeptide, forming a protein.
Q68. The structural backbone of DNA consists of:
(a) Sugar-phosphate units
(b) Nitrogenous bases
(c) Amino acids
(d) Fatty acids
Answer: (a) Sugar-phosphate units
Explanation: The DNA backbone is made of alternating sugar (deoxyribose) and phosphate groups. The nitrogenous bases are attached to the sugar molecules.
Q69. Which enzyme is responsible for joining Okazaki fragments during DNA replication?
(a) DNA polymerase
(b) Helicase
(c) Ligase
(d) Primase
Answer: (c) Ligase
Explanation: DNA ligase seals the nicks between Okazaki fragments on the lagging strand during DNA replication, creating a continuous DNA strand.
Q70. Which of the following nitrogenous bases pairs with cytosine in DNA?
(a) Adenine
(b) Thymine
(c) Guanine
(d) Uracil
Answer: (c) Guanine
Explanation: In DNA, cytosine pairs with guanine through three hydrogen bonds, maintaining the structure of the double helix.
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