DNA Computing MCQs (Multiple-Choice Questions)

1. What is DNA computing?

1. A computing method that uses only silicon transistors
2. A computing approach that uses DNA molecules and biochemical processes to represent and process information
3. A method that stores all data exclusively on magnetic disks
4. A computing technique based entirely on mechanical gears

Answer: B) A computing approach that uses DNA molecules and biochemical processes to represent and process information

Explanation:

DNA computing uses DNA sequences and molecular reactions to encode data and perform computational tasks. Depending on the approach, it may use operations such as hybridization, amplification, and molecular selection to solve specific problems.

2. What does DNA stand for?

1. Deoxyribonucleic acid
2. Digital nucleotide algorithm
3. Dynamic network architecture
4. Distributed numerical array

Answer: A) Deoxyribonucleic acid

Explanation:

DNA stands for deoxyribonucleic acid. It is a biological molecule that stores genetic information and can also serve as a medium for molecular information encoding in DNA computing.

3. Which four nitrogenous bases are found in DNA?

1. Adenine, uracil, cytosine, and guanine
2. Adenine, thymine, uracil, and guanine
3. Adenine, thymine, cytosine, and guanine
4. Thymine, uracil, cytosine, and ribose

Answer: C) Adenine, thymine, cytosine, and guanine

Explanation:

The four standard DNA bases are adenine (A), thymine (T), cytosine (C), and guanine (G). Uracil is generally found in RNA instead of thymine.

4. Which DNA bases form complementary pairs in standard double-stranded DNA?

1. Adenine with cytosine and thymine with guanine
2. Adenine with guanine and cytosine with thymine
3. Adenine with uracil and cytosine with guanine
4. Adenine with thymine and cytosine with guanine

Answer: D) Adenine with thymine and cytosine with guanine

Explanation:

In standard DNA base pairing, adenine pairs with thymine, while cytosine pairs with guanine. These complementary interactions allow DNA strands to recognize and bind to matching sequences, a property used in DNA-based computation.

5. Who introduced the influential DNA computing approach for solving the directed Hamiltonian path problem?

1. Alan Turing
2. Leonard Adleman
3. Claude Shannon
4. John von Neumann

Answer: B) Leonard Adleman

Explanation:

Leonard Adleman demonstrated DNA-based computation in 1994 by using molecular techniques to solve a small instance of the directed Hamiltonian path problem. His work helped establish DNA computing as a research field.

6. What is the primary role of DNA strands in a DNA computing system?

1. To represent encoded information through nucleotide sequences
2. To function as conventional silicon transistors
3. To generate magnetic fields for every calculation
4. To replace every laboratory instrument

Answer: A) To represent encoded information through nucleotide sequences

Explanation:

A DNA strand contains an ordered sequence of nucleotide bases. A DNA computing algorithm can map data, candidate solutions, or logical states to designed sequences and then use molecular interactions to manipulate or identify them.

7. What is DNA hybridization?

1. The conversion of DNA into a silicon chip
2. The permanent destruction of every nucleotide
3. The binding of complementary nucleic acid strands through base pairing
4. The transformation of DNA into an electrical wire

Answer: C) The binding of complementary nucleic acid strands through base pairing

Explanation:

Hybridization occurs when complementary DNA or other nucleic acid strands bind through base pairing. DNA computing can exploit this selective binding to identify matching sequences and perform molecular operations.

8. Which enzyme is commonly used to amplify selected DNA sequences?

1. DNA ligase
2. RNA polymerase
3. Restriction endonuclease
4. DNA polymerase

Answer: D) DNA polymerase

Explanation:

DNA polymerase synthesizes DNA using a template strand. In polymerase chain reaction (PCR), a DNA polymerase is used in repeated temperature cycles to amplify a target sequence. PCR is a common tool for preparing and analyzing DNA in molecular computing experiments.

9. What is the purpose of polymerase chain reaction (PCR) in DNA computing?

1. To convert all DNA into protein
2. To amplify selected DNA sequences
3. To eliminate complementary base pairing
4. To convert a DNA sequence directly into a computer program

Answer: B) To amplify selected DNA sequences

Explanation:

PCR produces many copies of a selected DNA region. In DNA computing, amplification can increase the amount of a target sequence so that it can be detected or used in subsequent molecular operations.

10. Which enzyme joins DNA fragments by forming phosphodiester bonds?

1. DNA ligase
2. Amylase
3. Protease
4. Lipase

Answer: A) DNA ligase

Explanation:

DNA ligase joins compatible DNA fragments by sealing breaks in the sugar-phosphate backbone. This activity can be useful when constructing DNA molecules that represent data or computational states.

11. What is a restriction endonuclease?

1. A device that measures electrical current
2. A protein that translates DNA directly into binary machine code
3. An enzyme that cuts DNA at particular recognition sequences or related sites
4. A molecule that stores data on a magnetic surface

Answer: C) An enzyme that cuts DNA at particular recognition sequences or related sites

Explanation:

Restriction endonucleases recognize particular DNA sequences and cleave DNA at defined positions. They can be used to manipulate DNA molecules and perform sequence-dependent operations in laboratory workflows.

12. What is a major advantage of DNA as an information-storage medium?

1. DNA never degrades under any conditions
2. DNA requires no preparation or reading equipment
3. DNA can be accessed instantaneously without laboratory procedures
4. DNA can store large amounts of information in a very small physical volume

Answer: D) DNA can store large amounts of information in a very small physical volume

Explanation:

DNA has a high theoretical information density, allowing large quantities of data to be represented in a small mass of material. Practical DNA storage also requires synthesis, sequencing, error correction, and suitable environmental conditions for long-term preservation.

13. Which type of computing is most closely associated with DNA computing?

1. Molecular computing
2. Mechanical computing only
3. Analog computing using vacuum tubes only
4. Conventional magnetic disk computing only

Answer: A) Molecular computing

Explanation:

DNA computing is a form of molecular computing because it uses molecules and biochemical reactions to encode and manipulate information. It differs from conventional digital computing in its physical mechanisms and operational constraints.

14. How can a DNA computing system represent a binary value?

1. Only by changing the physical size of a laboratory container
2. By assigning designed nucleotide sequences to binary states
3. Only by measuring the temperature of the room
4. By removing all bases from a DNA strand

Answer: B) By assigning designed nucleotide sequences to binary states

Explanation:

A DNA computing design can map particular nucleotide sequences to logical states such as 0 and 1. The encoding scheme must be designed carefully so that sequences can be distinguished and unwanted interactions are minimized.

15. What does molecular parallelism mean in DNA computing?

1. Every DNA molecule must perform exactly one operation sequentially
2. All computations must be carried out by a single molecule
3. Many molecular instances can participate in reactions at the same time
4. DNA molecules cannot interact with one another

Answer: C) Many molecular instances can participate in reactions at the same time

Explanation:

A DNA solution can contain vast numbers of molecules that participate in biochemical reactions concurrently. This molecular parallelism can be useful for exploring many candidate states, although reaction time, reagent availability, noise, and result extraction limit practical performance.

16. What is a major limitation of DNA computing compared with conventional electronic computing?

1. DNA cannot represent any information
2. DNA computing is incapable of performing any selection operation
3. DNA molecules cannot form complementary pairs
4. Laboratory reactions and result extraction can be slow and resource-intensive

Answer: D) Laboratory reactions and result extraction can be slow and resource-intensive

Explanation:

DNA computing often requires carefully controlled biochemical reactions, sample preparation, separation, and measurement. These processes can make end-to-end computation slower and more complex than many electronic operations, despite the high potential for molecular parallelism.

17. What is DNA sequencing?

1. Determining the order of nucleotide bases in a DNA molecule
2. Converting every DNA strand into a protein
3. Measuring only the mass of a computer processor
4. Joining DNA fragments without reading their bases

Answer: A) Determining the order of nucleotide bases in a DNA molecule

Explanation:

DNA sequencing determines the order of bases in a DNA molecule. DNA computing systems may use sequencing to read encoded information, identify candidate solutions, or verify the outcome of a molecular operation.

18. Which technique can separate DNA fragments according to their size?

1. Chromatography of proteins only
2. Gel electrophoresis
3. Optical character recognition
4. Digital image compression

Answer: B) Gel electrophoresis

Explanation:

Gel electrophoresis separates DNA fragments by moving them through a gel under an electric field. Fragment mobility depends strongly on length under standard DNA electrophoresis conditions, allowing researchers to analyze products of molecular reactions.

19. What is the main purpose of using fluorescent labels in some DNA assays?

1. To permanently increase the length of every DNA strand
2. To prevent all hybridization reactions
3. To make selected molecules detectable through emitted or measured fluorescence
4. To replace nucleotide bases with silicon transistors

Answer: C) To make selected molecules detectable through emitted or measured fluorescence

Explanation:

Fluorescent labels allow selected DNA molecules or reaction products to be detected using appropriate instruments. Fluorescence-based assays can help identify the presence, amount, or location of molecular targets in a DNA computing workflow.

20. Which computational problem was addressed in Adleman's original DNA computing experiment?

1. Sorting every possible real number
2. Training a modern large language model
3. Breaking all encryption algorithms
4. The directed Hamiltonian path problem for a small graph

Answer: D) The directed Hamiltonian path problem for a small graph

Explanation:

Adleman's experiment used DNA molecules to represent paths through a graph and biochemical techniques to select candidate paths. The demonstration showed how molecular operations could be organized into a computation for a small instance of the directed Hamiltonian path problem.

21. What is the Hamiltonian path problem?

1. Finding a path that visits every vertex exactly once, subject to the graph's edge directions when applicable
2. Finding the largest DNA molecule in a sample
3. Determining the melting point of every nucleotide
4. Finding a path that must repeat every vertex several times

Answer: A) Finding a path that visits every vertex exactly once, subject to the graph's edge directions when applicable

Explanation:

The Hamiltonian path problem asks whether a graph contains a path that visits each vertex exactly once. In a directed graph, each step must follow a directed edge. It is a classic computational problem used to illustrate DNA-based computation.

22. Why can DNA computing be considered a form of unconventional computing?

1. It can only perform conventional transistor switching
2. It uses biochemical and molecular processes rather than relying solely on standard electronic circuits
3. It cannot encode or process information
4. It requires every operation to be performed manually without molecules

Answer: B) It uses biochemical and molecular processes rather than relying solely on standard electronic circuits

Explanation:

Unconventional computing explores computational mechanisms beyond traditional electronic architectures. DNA computing uses molecular interactions and laboratory operations as part of the computation, creating opportunities and challenges that differ from conventional processors.

23. What is the role of a DNA primer in PCR?

1. To remove every nucleotide from the template
2. To convert DNA directly into electrical power
3. To provide a starting point for DNA polymerase synthesis
4. To prevent DNA polymerase from binding to DNA

Answer: C) To provide a starting point for DNA polymerase synthesis

Explanation:

A primer is a short nucleic acid sequence that binds to a complementary region of the template. DNA polymerase extends from the primer's 3′ end during DNA synthesis, enabling targeted amplification in PCR.

24. Which statement about DNA computing and massive parallelism is correct?

1. Massive parallelism guarantees that every problem can be solved instantly
2. Parallelism eliminates the need to extract computational results
3. Every molecular reaction must occur in a separate computer processor
4. Many candidate molecules can be processed concurrently, but managing and reading the results remains important

Answer: D) Many candidate molecules can be processed concurrently, but managing and reading the results remains important

Explanation:

DNA solutions can contain large populations of molecules that undergo reactions simultaneously. However, the number of candidates can grow rapidly, and the system still needs methods to control reactions, eliminate invalid candidates, and identify the correct result.

25. What does a DNA computing algorithm typically require in addition to encoding information in DNA?

1. A plan for molecular operations and a method for identifying the result
2. A guarantee that all molecules behave perfectly
3. The complete removal of every biochemical reaction
4. A requirement to use only mechanical computation

Answer: A) A plan for molecular operations and a method for identifying the result

Explanation:

A DNA computing algorithm must specify how input data is encoded, which molecular operations are performed, how unwanted candidates are removed or distinguished, and how the final result is detected. Molecular reactions alone do not automatically provide a complete computational solution.

26. What is the function of a DNA microarray in molecular analysis?

1. To manufacture conventional CPUs
2. To examine interactions or hybridization involving many DNA probes arranged on a surface
3. To replace all DNA molecules with magnetic particles
4. To sequence proteins using only mechanical force

Answer: B) To examine interactions or hybridization involving many DNA probes arranged on a surface

Explanation:

A DNA microarray contains many immobilized DNA probes at defined locations. Labeled target molecules can hybridize with complementary probes, enabling parallel analysis of many sequences. Related array-based approaches can support molecular detection and information-processing research.

27. Why is error correction important in DNA data storage and computing?

1. It makes every DNA molecule chemically identical
2. It eliminates the need to read stored information
3. It helps detect or recover information affected by synthesis, sequencing, or molecular errors
4. It guarantees that DNA never degrades

Answer: C) It helps detect or recover information affected by synthesis, sequencing, or molecular errors

Explanation:

DNA synthesis, amplification, storage, and sequencing can introduce substitutions, insertions, deletions, or missing sequences. Error-detection and error-correction methods add redundancy or structured encoding so that the intended information can be recovered more reliably.

28. What is one difference between DNA data storage and DNA computing?

1. DNA data storage cannot use nucleotide sequences
2. DNA computing never uses biochemical reactions
3. DNA storage must always solve graph problems
4. DNA data storage focuses on encoding and retrieving information, while DNA computing uses molecular processes to perform computational operations

Answer: D) DNA data storage focuses on encoding and retrieving information, while DNA computing uses molecular processes to perform computational operations

Explanation:

DNA data storage primarily represents information in DNA sequences for later retrieval. DNA computing uses DNA molecules and molecular reactions to carry out operations on encoded data. The fields can overlap, but their principal goals differ.

29. Which factor can affect the reliability of DNA hybridization?

1. Sequence complementarity and reaction conditions such as temperature and salt concentration
2. The color of the computer keyboard
3. The screen resolution of a laptop
4. The number of files stored on a hard disk

Answer: A) Sequence complementarity and reaction conditions such as temperature and salt concentration

Explanation:

Hybridization depends on sequence matching and physical conditions that affect nucleic acid binding. Temperature, salt concentration, strand length, and sequence composition influence binding stability and selectivity, making reaction design important in DNA computing.

30. What is the purpose of denaturation during PCR?

1. To join two DNA fragments permanently
2. To separate the two strands of double-stranded DNA
3. To convert DNA into a protein
4. To sequence every base without any instrument

Answer: B) To separate the two strands of double-stranded DNA

Explanation:

During PCR denaturation, heating separates double-stranded DNA into single strands. Primers can then bind during the annealing stage, and DNA polymerase extends them during the extension stage.

31. Which feature makes DNA molecules suitable for sequence-specific recognition?

1. They always conduct electricity like copper
2. They have no interactions with other DNA molecules
3. Complementary base pairing allows matching sequences to bind selectively
4. They contain only one possible nucleotide sequence

Answer: C) Complementary base pairing allows matching sequences to bind selectively

Explanation:

Complementary base pairing provides a molecular recognition mechanism. A designed DNA strand can bind to a matching sequence, allowing DNA computing systems to detect, combine, or select molecular states based on sequence information.

32. What is a major challenge in scaling DNA computing to more complex problems?

1. DNA cannot contain sequences longer than a few bases
2. Molecular reactions cannot occur in parallel
3. DNA molecules cannot be synthesized in laboratories
4. The number of candidate molecules, reaction complexity, and result extraction requirements can become difficult to manage

Answer: D) The number of candidate molecules, reaction complexity, and result extraction requirements can become difficult to manage

Explanation:

Complex problems can require huge candidate spaces and multiple molecular operations. Preparing enough material, controlling reaction specificity, limiting errors, and extracting a meaningful answer can become costly and technically challenging.

33. How can DNA computing support certain search problems?

1. By encoding candidate solutions in DNA and using molecular operations to filter or identify candidates
2. By eliminating all possible candidate solutions before computation begins
3. By guaranteeing a solution without representing the problem
4. By converting every search problem into a simple arithmetic operation

Answer: A) By encoding candidate solutions in DNA and using molecular operations to filter or identify candidates

Explanation:

A DNA computing system can represent candidate solutions as molecular sequences and use hybridization, amplification, separation, or other biochemical methods to select candidates that satisfy specified conditions. The efficiency of the entire workflow depends on the problem and experimental design.

34. What does biocomputing generally refer to?

1. Computing performed only with conventional silicon chips
2. Computing approaches that use biological materials, systems, or processes to store or process information
3. A method for increasing computer monitor brightness
4. A technique for repairing mechanical keyboards

Answer: B) Computing approaches that use biological materials, systems, or processes to store or process information

Explanation:

Biocomputing is a broad term for approaches that use biological molecules, cells, or processes for information processing or storage. DNA computing is one example, alongside other research involving biological systems and molecular computation.

35. Why is contamination control important in DNA computing experiments?

1. Contamination always improves reaction specificity
2. DNA computing does not involve physical samples
3. Unwanted DNA can introduce incorrect signals or interfere with intended molecular reactions
4. Contamination affects only electronic circuits, not biochemical experiments

Answer: C) Unwanted DNA can introduce incorrect signals or interfere with intended molecular reactions

Explanation:

Contaminating DNA may bind to probes, amplify during PCR, or appear as an unintended result. Clean laboratory procedures and suitable controls help distinguish genuine computational outcomes from artifacts.

36. What is the role of a control sample in a DNA computing experiment?

1. To replace every test sample with a different material
2. To guarantee that all reactions succeed
3. To eliminate the need for measurements
4. To provide a reference for assessing whether observed results are meaningful

Answer: D) To provide a reference for assessing whether observed results are meaningful

Explanation:

Control samples help researchers interpret experimental results by showing expected behavior under known conditions. Positive and negative controls can help identify failed reactions, contamination, and nonspecific signals.

37. What is a DNA strand's melting temperature commonly associated with?

1. The temperature at which a population of double-stranded DNA molecules becomes approximately half denatured under specified conditions
2. The temperature at which DNA turns into a metal
3. The temperature at which all chemical reactions stop permanently
4. The temperature at which every DNA sequence becomes identical

Answer: A) The temperature at which a population of double-stranded DNA molecules becomes approximately half denatured under specified conditions

Explanation:

The melting temperature, often written as Tm, is commonly defined as the temperature at which about half of a DNA duplex population is denatured under specified conditions. It depends on factors such as sequence composition, strand length, salt concentration, and mismatches.

38. Which statement best describes the relationship between DNA computing and conventional computers?

1. DNA computing has already made conventional computers unnecessary
2. DNA computing may complement conventional systems for selected tasks but does not automatically replace general-purpose electronic processors
3. Conventional computers cannot analyze DNA sequences
4. DNA computing cannot be combined with electronic measurement equipment

Answer: B) DNA computing may complement conventional systems for selected tasks but does not automatically replace general-purpose electronic processors

Explanation:

DNA computing offers alternative molecular mechanisms that may be useful for specific computational or storage problems. Conventional computers remain well suited to general-purpose processing, and DNA-based systems often depend on electronic instruments for control, analysis, and data interpretation.

39. What is one possible application of DNA-based information processing in medicine?

1. Replacing all clinical testing without collecting samples
2. Guaranteeing that every disease can be cured through hybridization
3. Using sequence recognition and molecular reactions in diagnostic or biosensing systems
4. Eliminating the need to validate diagnostic results

Answer: C) Using sequence recognition and molecular reactions in diagnostic or biosensing systems

Explanation:

DNA-based methods can detect specific nucleic acid sequences and support molecular diagnostics or biosensors. These approaches require appropriate validation, controls, and performance evaluation before clinical use.

40. What is the purpose of designing DNA sequences with minimal unintended cross-hybridization?

1. To make all sequences bind to every other sequence
2. To increase random molecular interactions
3. To eliminate the need for complementary base pairing
4. To reduce unwanted binding between sequences that are not intended to interact

Answer: D) To reduce unwanted binding between sequences that are not intended to interact

Explanation:

DNA sequence design considers both intended hybridization and unwanted interactions. Reducing cross-hybridization helps improve the specificity and reliability of molecular operations in a DNA computing system.

41. Which statement about DNA computing's theoretical information density is correct?

1. DNA can encode substantial information per unit mass, but practical storage requires additional encoding, handling, and retrieval processes
2. DNA cannot encode information in its base sequence
3. Theoretical information density means reading data requires no time
4. DNA storage is immune to every possible form of error

Answer: A) DNA can encode substantial information per unit mass, but practical storage requires additional encoding, handling, and retrieval processes

Explanation:

DNA's sequence of four bases can represent digital information at high density. However, practical systems must account for synthesis costs, sequencing errors, redundancy, sample handling, and the time required to read the encoded data.

42. What is one purpose of using short DNA oligonucleotides in a molecular computing design?

1. To guarantee that every molecular reaction is error-free
2. To provide designed sequences that can act as probes, primers, or molecular building blocks
3. To prevent all DNA synthesis from occurring
4. To convert biological information directly into mechanical motion

Answer: B) To provide designed sequences that can act as probes, primers, or molecular building blocks

Explanation:

Oligonucleotides are short DNA or RNA sequences synthesized for specific purposes. In DNA computing, they can serve as primers, probes, tags, or components of molecular structures used to encode and manipulate information.

43. Why is it important to distinguish computational parallelism from overall execution time in DNA computing?

1. Parallelism means that laboratory operations never take time
2. Parallelism removes all input and output requirements
3. Many molecular reactions can occur concurrently, but preparation, reaction completion, separation, and readout still contribute to total execution time
4. Parallelism guarantees that a DNA computing system outperforms every electronic processor

Answer: C) Many molecular reactions can occur concurrently, but preparation, reaction completion, separation, and readout still contribute to total execution time

Explanation:

Molecular parallelism can allow many candidate molecules to react simultaneously. However, total runtime includes the complete experimental workflow, not just the time during which reactions occur. Performance comparisons must include preparation and result extraction.

44. Which statement correctly distinguishes DNA computing from quantum computing?

1. DNA computing always relies on quantum entanglement as its primary computational mechanism
2. Quantum computing cannot use physical molecules
3. DNA computing is identical to conventional transistor-based computing
4. DNA computing uses molecular and biochemical operations, whereas quantum computing relies on controlled quantum states and operations

Answer: D) DNA computing uses molecular and biochemical operations, whereas quantum computing relies on controlled quantum states and operations

Explanation:

DNA computing typically uses molecular encoding and biochemical reactions. Quantum computing uses quantum states and operations, such as superposition and entanglement in applicable algorithms. A DNA-based system is not automatically a quantum computer.

45. What is a potential challenge when using DNA computing for real-time applications?

1. Biochemical reaction times and laboratory processing may not meet the required response time
2. DNA molecules always respond faster than electronic circuits
3. DNA computing cannot encode input data
4. Every DNA-based system must use a mechanical clock

Answer: A) Biochemical reaction times and laboratory processing may not meet the required response time

Explanation:

Some real-time applications require predictable, very low latency. DNA-based operations can involve sample preparation, reaction incubation, separation, and detection, which may make them unsuitable for time-critical tasks that electronic systems can perform much faster.

46. What does molecular recognition mean in DNA computing?

1. The recognition of a computer monitor by an electronic sensor
2. The selective interaction of molecules based on properties such as complementary sequence matching
3. The conversion of DNA into a magnetic storage device
4. The physical identification of a laboratory worker

Answer: B) The selective interaction of molecules based on properties such as complementary sequence matching

Explanation:

Molecular recognition occurs when molecules interact selectively because of structural or chemical compatibility. In DNA computing, complementary base pairing provides an important mechanism for recognizing particular sequences and carrying out selective molecular operations.

47. Why is result verification important after a DNA computation?

1. Because a molecular reaction always proves that the intended algorithm succeeded
2. Because DNA results never contain errors
3. Because detected molecular products must be checked to confirm that they represent valid computational outcomes
4. Because verification prevents any data from being read

Answer: C) Because detected molecular products must be checked to confirm that they represent valid computational outcomes

Explanation:

A detected DNA sequence may arise from the intended computation, contamination, incomplete reactions, or nonspecific binding. Verification methods help establish whether the observed products satisfy the problem's requirements and whether the computational result is reliable.

48. Which statement best describes the future potential of DNA computing?

1. It will necessarily replace every digital computer in the near future
2. It cannot be used in any practical research application
3. It eliminates all limitations associated with information storage
4. It may offer specialized solutions in molecular information processing, selected search tasks, and high-density data storage

Answer: D) It may offer specialized solutions in molecular information processing, selected search tasks, and high-density data storage

Explanation:

DNA computing and DNA data storage continue to be explored for applications where molecular properties offer distinctive benefits. Practical adoption depends on improvements in reliability, cost, speed, scalability, and the ability to integrate molecular operations with conventional systems.

49. A DNA computing experiment produces 1,000 candidate DNA strands. A filtering operation removes 760 candidates. How many candidate strands remain after filtering?

1. 240
2. 260
3. 760
4. 1,760

Answer: A) 240

Explanation:

Initial candidate strands = 1,000.

Removed candidate strands = 760.

Remaining candidates = Initial candidates − Removed candidates.

Remaining candidates = 1,000 − 760 = 240.

Therefore, 240 candidate DNA strands remain after filtering.

50. A DNA data-storage system encodes 2,400 bits of information. Each synthesized DNA strand is designed to carry 120 data bits, excluding additional error-correction and indexing overhead. What is the minimum number of DNA strands required to encode the information?

1. 10 strands
2. 15 strands
3. 20 strands
4. 24 strands

Answer: C) 20 strands

Explanation:

Total information = 2,400 bits.

Data capacity per DNA strand = 120 bits.

Minimum number of strands = Total information ÷ Capacity per strand.

Minimum number of strands = 2,400 ÷ 120 = 20.

Therefore, at least 20 DNA strands are required under the stated assumptions. A practical system may need additional strands for error correction, indexing, redundancy, and other overheads.