All Free Biology MCQs with Answers

4701. The E. coli genome consists of base pairs:

• A. 4,639,221
• B. 4,639,222
• C. 4,629,221
• D. 4,638,221

Explanation: The E. coli genome consists of exactly 4,639,221 base pairs. This number is significant because it provides the genetic blueprint for the organism, encoding genes responsible for at least 4,288 proteins. The other options are incorrect as they either add or subtract a small number of base pairs, which does not reflect the established scientific consensus.

4702. Like DNA _ is a polymer of ribonucleotides.

• A. ATP
• B. NAD
• C. FAD
• D. RNA

Explanation: The correct answer is RNA. RNA, or ribonucleic acid, is a polymer composed of ribonucleotides, just as DNA is a polymer of deoxyribonucleotides. RNA is crucial for various biological functions, including acting as a messenger between DNA and the protein synthesis machinery. The other options, ATP, NAD, and FAD, are not polymers; instead, they are individual molecules or coenzymes that play different roles in cellular processes. ATP is a single nucleotide used for energy transfer, NAD is a coenzyme involved in electron transport, and FAD is a coenzyme involved in redox reactions.

4703. Transfer RNA comprises about _ % of the cellular RNA.

• A. 3 to 4
• B. 5 to 6
• C. 80
• D. 10 to 20

Explanation: It is intermediate in quantity among three types of RNAs.

4704. DNA was discovered by:

• A. A French chemist
• B. A German chemist
• C. A Swiss chemist
• D. A Spanish chemist

Explanation: The molecule now known as DNA was first identified by Johann Friedrich Miescher, a Swiss chemist, in the 1860s. He was studying the composition of white blood cells and discovered the nucleic acid in the cell nuclei, which he termed 'nuclein.' The other options are incorrect because no French, German, or Spanish chemist is credited with the discovery of DNA.

4705. Who discovered DNA?

• A. Frederick Miescher
• B. Frederick Sanger
• C. Frederick Griffith
• D. Frederick Aldrich

Explanation: Frederick Miescher, a Swiss chemist, is credited with the discovery of DNA in 1869 when he isolated a substance he named 'nuclein' from the nuclei of cells. This substance was later understood to be DNA. The other options refer to scientists associated with different contributions to biology and genetics. Frederick Sanger developed methods for sequencing DNA, Frederick Griffith discovered the transforming principle, and Frederick Aldrich is not relevant to this context.

4706. Nucleic acids were named so due to:

• A. Their isolation from nuclei
• B. Their isolation from pus cells
• C. Their acidic nature
• D. Their isolation from nucleus and acidic nature

Explanation: The term 'nucleic acids' originates from their initial isolation from cell nuclei ('nucleic') and their acidic nature ('acids'). Option D is correct as it encompasses both these reasons for the naming. Options A and C only partially explain the naming, while Option B is irrelevant to the origin of the term.

4707. Mostly occurs in the nuclei of the cells but in lesser amount outside the nucleus as well:

• A. RNA
• B. Proteins
• C. Nucleic acids
• D. DNA

Explanation: DNA is the primary genetic material located in the nucleus of eukaryotic cells, where it forms chromosomes and genes. It is also present in smaller amounts in organelles like mitochondria and chloroplasts, which have their own DNA, known as extranuclear or organelle DNA. This distinguishes DNA from RNA, which primarily functions in the cytoplasm, and proteins, which are not nucleic acids but rather the products of genetic instructions. Nucleic acids as a category include both DNA and RNA, but the question specifically refers to the location mostly in the nuclei, making DNA the correct answer.

4708. It is mostly present in the nucleolus, in the ribosomes, in the cytosol and in smaller amounts in other parts of the cell as well:

• A. DNA
• B. RNA
• C. Proteins
• D. Nucleic acids

Explanation: RNA being associated with protein synthesis mostly occurs in cytoplasmhowever it is synthesized inside the nucleus from DNA that is why it always occurs in nucleus as well.

4709. They are polymers of units called nucleotides:

• A. Amino acids
• B. Nucleosides
• C. Fatty acids
• D. Nucleic acids

Explanation: Nucleic acids are polymers made up of monomeric units called nucleotides. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. DNA and RNA are the two primary types of nucleic acids, responsible for genetic information storage and transfer. In contrast, amino acids form proteins, fatty acids are components of lipids, and nucleosides are components of nucleotides, lacking the phosphate group essential for forming the nucleic acid backbone.

4710. Each nucleotide is made up of:

• A. One subunit
• B. Two subunits
• C. Three subunits
• D. Four subunits

Explanation: A nucleotide is the basic building block of nucleic acids, such as DNA and RNA. It consists of three essential components: a pentose sugar (either ribose or deoxyribose), a nitrogenous base (such as adenine, thymine, cytosine, guanine, or uracil), and a phosphate group. Each of these components plays a crucial role in the structure and function of nucleic acids. Options A, B, and D are incorrect because they do not accurately reflect the number of subunits in a nucleotide.