1. Which statement best describes the molecular basis of inheritance?
ⓐ. Hereditary information is encoded in nucleic acids and expressed through cellular products.
ⓑ. Hereditary information is stored only in membrane lipids and released during growth.
ⓒ. Hereditary information is carried mainly by polysaccharides that build cell walls.
ⓓ. Hereditary information passes through mineral salts dissolved in body fluids.
Correct Answer: Hereditary information is encoded in nucleic acids and expressed through cellular products.
Explanation: Inheritance at the molecular level is based on nucleic acids, especially DNA in most organisms. Genes carry information in a chemical form that can be used by the cell. That information is not valuable merely as stored material; it is expressed through functional products that influence characters. This idea links heredity with molecular structure and cellular activity.
2. In most organisms, the principal hereditary material is
ⓐ. protein molecule
ⓑ. DNA molecule
ⓒ. starch polymer
ⓓ. lipid molecule
Correct Answer: DNA molecule
Explanation: DNA serves as the chief storehouse of hereditary information in most organisms. Its sequence preserves genetic instructions that can be copied and transmitted across generations. Proteins, lipids, and polysaccharides perform important cellular roles, but they are not the usual material of inheritance. This is why DNA is described as the principal genetic material in living systems.
3. Which statement correctly compares DNA and RNA in relation to heredity?
ⓐ. RNA is the only hereditary material found in all organisms.
ⓑ. DNA and RNA both serve only metabolic roles and not hereditary ones.
ⓒ. DNA is the main genetic material in most organisms, whereas RNA serves that role in some viruses.
ⓓ. DNA occurs only in eukaryotes, whereas RNA carries heredity in prokaryotes.
Correct Answer: DNA is the main genetic material in most organisms, whereas RNA serves that role in some viruses.
Explanation: Both DNA and RNA are nucleic acids, but they are not used identically in all biological systems. Most organisms use DNA as their main hereditary material, while some viruses use RNA instead. This comparison is important because it shows that nucleic-acid-based inheritance is broader than DNA alone. It also prevents the mistaken idea that RNA can never carry genetic information.
4. A virus is shown to transmit its characters through an RNA molecule. This indicates that
ⓐ. proteins alone can store genetic information
ⓑ. DNA must be absent from all cells
ⓒ. RNA has no role in molecular inheritance
ⓓ. RNA can function as genetic material in some biological systems
Correct Answer: RNA can function as genetic material in some biological systems
Explanation: Certain viruses keep their hereditary information in RNA rather than DNA. That observation shows that RNA is capable of carrying genetic instructions. It does not mean proteins replace nucleic acids in inheritance, and it does not deny the major role of DNA in most organisms. The key conclusion is that genetic material can be RNA in specific cases.
5. A hereditary unit affects a phenotype most directly when the information it carries is used to produce
ⓐ. stored glycogen granules
ⓑ. a functional RNA or protein
ⓒ. extra water reserves
ⓓ. reserve lipid droplets
Correct Answer: a functional RNA or protein
Explanation: A gene influences a trait when its information is expressed in a usable molecular form. That functional product may be an RNA molecule or a protein, depending on the role of the gene. Phenotype is therefore linked not just to inheritance of information, but also to its expression. Without such expression, the stored information would not produce a visible or functional effect.
6. Which option best connects classical Mendelian ideas with molecular biology?
ⓐ. Mendelian factors are mineral crystals deposited outside living cells.
ⓑ. Mendelian factors are digestive enzymes acting only in the alimentary canal.
ⓒ. Mendelian factors are cell pigments dissolved in the vacuole of tissues.
ⓓ. Mendelian factors are now understood as genes associated with nucleic-acid based information.
Correct Answer: Mendelian factors are now understood as genes associated with nucleic-acid based information.
Explanation: Mendel proposed invisible hereditary factors long before their chemical nature was known. Molecular biology later identified these factors with genes carried in nucleic acids. This connection explains how a classical idea of heredity became a molecular concept. It also marks the transition from observational genetics to biochemical understanding.
7. Assertion: RNA cannot act as genetic material.
Reason: DNA is the main genetic material in most organisms.
ⓐ. Both Assertion and Reason are true, and Reason correctly explains Assertion.
ⓑ. Both Assertion and Reason are true, but Reason does not explain Assertion.
ⓒ. Assertion is true, but Reason is false.
ⓓ. Assertion is false, but Reason is true.
Correct Answer: Assertion is false, but Reason is true.
Explanation: RNA is not excluded from heredity, because some viruses use RNA as their genetic material. At the same time, DNA is indeed the principal genetic material in most organisms. The reason statement is therefore correct, but it does not make the assertion true. This distinction helps separate the general rule from the known exception.
8. Which sequence best shows the broad route from hereditary information to expression of a character in most organisms?
ⓐ. Protein → RNA → DNA
ⓑ. Lipid → carbohydrate → DNA
ⓒ. DNA → RNA → functional product
ⓓ. Mineral ion → gene → membrane
Correct Answer: DNA → RNA → functional product
Explanation: The usual route of gene expression begins with information stored in DNA. That information is first transferred into RNA and is then used to produce a functional product, commonly a protein or functional RNA. Through this route, molecular information becomes an expressed character. The sequence captures the broad logic of how heredity is translated into biological effect.
9. Which group includes molecules that directly serve as hereditary material in living systems?
ⓐ. DNA and RNA
ⓑ. Proteins and lipids
ⓒ. Starch and glycogen
ⓓ. Cellulose and chitin
Correct Answer: DNA and RNA
Explanation: Hereditary information is carried by nucleic acids. DNA is the genetic material in most organisms, while RNA performs that role in some viruses. Proteins, lipids, and polysaccharides are important cellular substances, but they are not the standard information-storing molecules of inheritance. This is why nucleic acids occupy a central place in molecular genetics.
10. Which statement correctly explains why proteins are not considered the primary hereditary material in cells?
ⓐ. Proteins are present only outside the nucleus.
ⓑ. Proteins cannot influence cellular characters.
ⓒ. Proteins are found only in viruses.
ⓓ. Proteins do not provide the template-based copying system required of hereditary material.
Correct Answer: Proteins do not provide the template-based copying system required of hereditary material.
Explanation: A genetic material must preserve information and support accurate copying across generations. Nucleic acids do this through complementarity and template-directed replication. Proteins are vital functional molecules, but they do not serve as the usual self-copying hereditary framework.
11. Fill in the blank in the most accurate way:
In molecular terms, a gene is best understood as a unit of hereditary information present in ______.
ⓐ. membrane lipids
ⓑ. nucleic acid
ⓒ. structural polysaccharide
ⓓ. mineral salts
Correct Answer: nucleic acid
Explanation: Genes are molecular units of inheritance encoded in nucleic acids. In most organisms, this information is stored in DNA, though RNA can act as genetic material in some viruses. The defining idea is that heredity is chemically organized in an ordered nucleotide sequence. This view transformed genetics from an abstract theory into a molecular science.
12. Which statement best reflects the relation between stored hereditary information and its expression?
ⓐ. Stored information becomes useful only after it is converted into mineral nutrients.
ⓑ. Stored information remains permanently inactive in all cells.
ⓒ. Stored information can direct the formation of functional molecules that influence traits.
ⓓ. Stored information is expressed only when converted directly into lipids.
Correct Answer: Stored information can direct the formation of functional molecules that influence traits.
Explanation: The importance of genetic information lies in its ability to be expressed. A gene does not act as a trait by itself; rather, it directs the synthesis of functional molecules that affect cellular structure or activity. Through this process, molecular information is translated into observable characters. This link between storage and expression is a foundation of molecular biology.
13. Which statement is correct about the role of RNA in inheritance?
ⓐ. RNA can act as genetic material in some viruses.
ⓑ. RNA carries hereditary information only in prokaryotes.
ⓒ. RNA never participates in the flow of genetic information.
ⓓ. RNA is used only for energy storage in cells.
Correct Answer: RNA can act as genetic material in some viruses.
Explanation: RNA is not merely an intermediate molecule in all biological systems. In some viruses, it serves as the actual genetic material and carries hereditary instructions from one generation to the next. This fact broadens the concept of inheritance beyond DNA alone. It also supports the idea that nucleic acids, rather than proteins, are the true carriers of genetic information.
14. Which option best describes nucleic acids in relation to their basic structure?
ⓐ. They are polymers made of amino acids.
ⓑ. They are polymers made of fatty acids and glycerol.
ⓒ. They are polymers made of monosaccharides.
ⓓ. They are polymers made of nucleotides.
Correct Answer: They are polymers made of nucleotides.
Explanation: DNA and RNA are both long-chain polymers built from repeating nucleotide units. Each nucleotide contributes to the ordered sequence that stores biological information. This polymeric nature is essential because variation in nucleotide order creates different genes and genomes. Nucleic acids are therefore sequence-based information molecules.
15. Which quantity is most directly used to express the length of a DNA molecule?
ⓐ. number of amino acids
ⓑ. number of peptide bonds
ⓒ. number of base pairs
ⓓ. number of phospholipid layers
Correct Answer: number of base pairs
Explanation: DNA length is commonly expressed in base pairs because double-stranded DNA consists of paired bases along its length. This unit directly reflects the size of the nucleotide sequence. It is more meaningful for DNA than measures used for proteins or membranes. Genome size in organisms is therefore often stated in bp, kb, or larger related units.
16. Which of the following is correctly matched with the approximate DNA or genome size given here?
ⓐ. Human haploid DNA — 5386 nucleotides
ⓑ. $\phi$X174 — 5386 nucleotides
ⓒ. E. coli — 48502 bp
ⓓ. Lambda phage — $3.3 \times 10^9$ bp
Correct Answer: $\phi$X174 — 5386 nucleotides
Explanation: The genome of $\phi$X174 is a small nucleic-acid molecule of about 5386 nucleotides. The other values belong to different examples, such as lambda phage, E. coli, and human haploid DNA. Together, these examples show how widely genome size can vary among living systems.
17. Which organism is associated with a DNA size of about 48502 base pairs?
ⓐ. E. coli
ⓑ. human haploid cell
ⓒ. $\phi$X174
ⓓ. lambda phage
Correct Answer: lambda phage
Explanation: Lambda phage is listed with a genome size of about 48502 base pairs. This places it between very small genomes such as $\phi$X174 and much larger cellular genomes such as that of E. coli or humans. The comparison illustrates the wide range of DNA sizes found in biological systems. Genome size is therefore organism-specific rather than fixed across life forms.
18. Which one of the following is closest to the DNA size of E. coli?
ⓐ. $4.6 \times 10^6$ bp
ⓑ. 5386 nucleotides
ⓒ. 48502 bp
ⓓ. $3.3 \times 10^9$ bp
Correct Answer: $4.6 \times 10^6$ bp
Explanation: E. coli has a genome size of about $4.6 \times 10^6$ base pairs here. This makes it much larger than many viral genomes but far smaller than the human genome. The comparison highlights the scale difference between prokaryotic and viral or human DNA.
19. A scientist states that a human haploid cell contains about $3.3 \times 10^9$ units of DNA length. These units are best expressed as
ⓐ. amino acids
ⓑ. base pairs
ⓒ. ribosomes
ⓓ. peptide links
Correct Answer: base pairs
Explanation: Human haploid DNA length is described in terms of base pairs because DNA is a double-stranded molecule. Base-pair count is the standard measure used for genomic length. This way of expressing size is used from viruses to humans. It allows meaningful comparison across organisms with very different genome scales.
20. Which sequence correctly arranges the following examples from smallest to largest genetic-material size?
$\phi$X174, lambda phage, E. coli, human haploid DNA
ⓐ. human haploid DNA < E. coli < lambda phage < $\phi$X174
ⓑ. E. coli < lambda phage < $\phi$X174 < human haploid DNA
ⓒ. $\phi$X174 < lambda phage < E. coli < human haploid DNA
ⓓ. lambda phage < $\phi$X174 < human haploid DNA < E. coli
Correct Answer: $\phi$X174 < lambda phage < E. coli < human haploid DNA
Explanation: The listed sizes increase from the very small genome of $\phi$X174 to lambda phage, then to E. coli, and finally to human haploid DNA. This ordering highlights the dramatic increase in genome size from viruses to bacteria to humans.
