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📝 DNA (deoxyribonucleic acid) as genetic material (7 MCQs)

📖 From Campbell Biology • 1. Evolution and the theme of Biology and Scientific Inquiry • 7 questions available

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What is DNA (deoxyribonucleic acid) as genetic material?

Definition:
DNA, or deoxyribonucleic acid, is the molecule that stores hereditary information in most organisms. Its nucleotide sequence contains instructions that influence the production of proteins and functional RNA, allowing biological information to be maintained and transmitted between generations.

Working:
DNA stores information in the order of its nucleotides. During reproduction, DNA is copied so genetic information can be passed to new cells or offspring.

Example:
If a DNA region contains the sequence $A-T-G-C$ , its complementary strand contains $T-A-C-G$ . This complementary pairing helps DNA copying occur accurately.

Reason:
DNA is suitable as genetic material because it can store large amounts of information, be copied, and undergo changes that contribute to biological variation.

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Hard

📝 All DNA (deoxyribonucleic acid) as genetic material MCQs

Q1. A researcher needs to identify the molecule that carries hereditary information. Which observation would provide the strongest direct evidence that DNA, rather than protein, is the genetic material?

A.DNA is present in nearly all cells

B.Destroying DNA prevents hereditary information from being transferred, while destroying protein does not ✅

C.DNA contains four different nucleotide bases

D.Proteins have complex three-dimensional structures

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The strongest evidence comes from selectively destroying one candidate molecule and observing whether hereditary information is lost. If eliminating DNA prevents genetic information from being transferred while eliminating protein does not, DNA is directly implicated as the hereditary material.

Q2. Two cell populations receive identical environmental conditions. Population X contains DNA molecules that remain unchanged before and after cell division, while Population Y shows major DNA changes between generations. Which prediction is most reasonable?

A.Population X should show greater genetic continuity across generations ✅

B.Population Y must contain more proteins

C.Population X cannot undergo mutations

D.Population Y cannot reproduce successfully

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: Genetic information must be sufficiently stable to persist through cell division, although occasional changes can occur. Therefore, unchanged DNA across generations supports greater genetic continuity, whereas substantial DNA changes would increase the possibility of altered inherited traits.

Q3. A scientist introduces purified DNA from bacteria with Trait A into bacteria lacking Trait A. After treatment, some recipient cells permanently acquire Trait A and pass it to their descendants. What conclusion is best supported?

A.The DNA supplied energy for Trait A

B.The DNA acted as an inherited information source capable of changing the recipients ✅

C.The recipients produced Trait A only because proteins entered their membranes

D.Trait A appeared randomly and was unrelated to the treatment

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The key evidence is both acquisition and inheritance of the new trait. Because purified DNA was introduced and the resulting phenotype persisted in descendants, the DNA must have carried information capable of producing the inherited change.

Q4. A student argues, "DNA cannot be genetic material because it contains only four nucleotide types, whereas proteins contain many different amino acids." What is the most important flaw in this reasoning?

A.Genetic information depends on nucleotide sequences and their organization, not simply on the number of molecular building blocks ✅

B.DNA contains more than twenty nucleotide types

C.Proteins cannot contain genetic information under any circumstances

D.The number of DNA molecules determines every inherited trait

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: The student incorrectly assumes that informational capacity depends only on the number of building-block types. DNA can encode extensive information through the enormous number and specific order of nucleotide sequences, making four nucleotide types sufficient for complex hereditary instructions.

Q5. In an experiment, researchers measure the percentage of cells retaining an introduced hereditary trait after several generations. Group A receives DNA, Group B receives protein, and Group C receives no added material. The results are: A = 82%, B = 18%, C = 7%. Which interpretation is most justified?

A.DNA treatment is associated with much stronger stable inheritance than protein treatment or no treatment ✅

B.Protein must be the primary genetic material because some cells retained the trait

C.The control group proves that DNA is unnecessary

D.The results show that every DNA molecule automatically produces a new trait

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: The DNA-treated group has the highest frequency of stable inheritance, while the protein-treated and untreated groups show much lower frequencies. This pattern supports DNA as the stronger candidate for carrying hereditary information, although additional controls could strengthen causation.

Q6. A mutation changes one DNA nucleotide, but the organism's observable trait remains unchanged. A researcher concludes that DNA therefore cannot control inherited characteristics. Which response best evaluates the conclusion?

A.Correct, because every DNA change must alter phenotype

B.Incorrect, because some DNA changes may not alter the resulting biological function or phenotype ✅

C.Correct, because only proteins can store hereditary information

D.Incorrect, because DNA mutations always destroy cells

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The conclusion is too broad because a DNA change does not necessarily produce a visible phenotypic change. The altered sequence may have little functional effect, may be compensated by other processes, or may occur where its change does not affect the trait.

Q7. A laboratory compares three treatments on recipient cells: DNA alone produces a stable inherited trait in 76% of cells, protein alone produces it in 9%, and DNA plus a DNA-destroying enzyme produces it in 5%. Protein-destroying treatment leaves the DNA result at 73%. Which explanation best integrates these findings?

A.Protein is required for hereditary information, while DNA is only structural

B.DNA is strongly implicated as the information-carrying molecule because destroying DNA greatly reduces inheritance, whereas destroying protein has little effect ✅

C.Both DNA and protein are equally responsible because both treatments produce some inheritance

D.The results show that enzymes always create hereditary traits

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The comparison isolates the importance of DNA and protein. DNA alone produces frequent stable inheritance, destroying DNA nearly eliminates the effect, and destroying protein has little impact. Together, these results strongly support DNA as the molecule carrying the hereditary information.

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