DNA Fingerprinting Practice Questions
40 free DNA Fingerprinting practice questions for the Zoology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
DNA fingerprinting is primarily used to:
- A Determine relative levels of gene expression in tissue
- B Identify individuals based on DNA patterns
- C Sequence entire genomes
- D Detect chromosomal abnormalities only
Correct answer: Identify individuals based on DNA patterns
DNA fingerprinting analyzes specific DNA regions that vary among individuals. The resulting patterns can uniquely identify individuals except identical twins.
The principle of DNA fingerprinting is based on variation in:
- A Protein-coding DNA sequences
- B Mitochondrial DNA genes
- C Repetitive DNA sequences
- D Ribosomal RNA-encoding genes
Correct answer: Repetitive DNA sequences
DNA fingerprinting relies on highly polymorphic repetitive DNA regions. These repeats differ in number among individuals, producing unique patterns.
Which scientist is credited with developing DNA fingerprinting?
- A James Watson
- B Francis Crick
- C Alec Jeffreys
- D Kary Mullis, inventor of PCR
Correct answer: Alec Jeffreys
Alec Jeffreys developed DNA fingerprinting in 1984. His discovery revolutionized forensic science and genetic identification.
Which type of DNA repeats were first used in classical DNA fingerprinting?
- A SNPs
- B STRs
- C VNTRs
- D Microsatellites
Correct answer: VNTRs
VNTRs (Variable Number Tandem Repeats) were initially used due to their high variability. They generate distinct banding patterns among individuals.
Short Tandem Repeats (STRs) are preferred in modern DNA profiling because they:
- A Are present only in protein-coding regions of genes
- B Require large amounts of intact DNA
- C Can be amplified from small DNA samples
- D Do not vary among individuals
Correct answer: Can be amplified from small DNA samples
STRs are short repeat units that can be easily amplified using PCR. This makes them suitable for degraded or limited DNA samples.
Which technique is essential for amplifying DNA in DNA fingerprinting?
- A Gel electrophoresis
- B PCR
- C Southern blotting
- D DNA sequencing
Correct answer: PCR
PCR amplifies specific DNA regions exponentially. It allows analysis even when starting DNA quantity is very small.
Gel electrophoresis separates DNA fragments based on their:
- A Base composition
- B Charge
- C Size
- D Sequence
Correct answer: Size
DNA fragments move through a gel matrix according to size when an electric field is applied. Smaller fragments migrate faster than larger ones.
Southern blotting is used in DNA fingerprinting to:
- A Amplify target DNA sequences
- B Transfer DNA fragments to a membrane
- C Directly sequence each of the separated DNA fragments
- D Visualize proteins
Correct answer: Transfer DNA fragments to a membrane
Southern blotting transfers separated DNA fragments from a gel onto a membrane. This allows hybridization with labeled probes.
Molecular markers are best defined as:
- A Visible phenotypic traits of an organism
- B Proteins encoded by expressed genes
- C DNA sequences used to identify genetic variation
- D Entire intact chromosomes visible under a light microscope
Correct answer: DNA sequences used to identify genetic variation
Molecular markers are identifiable DNA sequences with known locations. They reveal genetic variation within and between populations.
Which molecular marker detects single base changes in DNA?
- A VNTR
- B STR
- C RFLP
- D SNP
Correct answer: SNP
SNPs represent single nucleotide variations in the genome. They are abundant and useful for fine-scale genetic analysis.
Restriction Fragment Length Polymorphism (RFLP) analysis depends on:
- A Polymerase chain reaction amplification of the region
- B Restriction enzyme digestion
- C In vitro transcription of RNA from the template
- D Analysis of overall protein expression levels
Correct answer: Restriction enzyme digestion
RFLP relies on restriction enzymes cutting DNA at specific sites. Variations in these sites produce fragments of different lengths.
Which application commonly uses DNA fingerprinting?
- A Determining blood groups
- B Forensic identification
- C Measuring enzyme activity
- D Detecting metabolic disorders only
Correct answer: Forensic identification
DNA fingerprinting is widely used in forensic science to match biological samples to individuals. It also aids in crime investigation.
In paternity testing, DNA fingerprinting is useful because:
- A Children inherit alleles from both parents
- B Only the paternal contribution is ever analyzed
- C DNA never changes across generations
- D All alleles are inherited solely from the mother
Correct answer: Children inherit alleles from both parents
A child inherits half of its DNA from each parent. Comparing DNA markers can confirm or exclude biological relationships.
Which molecular marker is co-dominant and highly polymorphic?
- A RAPD
- B AFLP
- C STR
- D ISSR
Correct answer: STR
STR markers are co-dominant, allowing detection of both alleles in heterozygotes. Their high variability makes them ideal for identification.
Random Amplified Polymorphic DNA (RAPD) markers are characterized by:
- A Very high experimental reproducibility across labs
- B Prior requirement of target sequence information
- C Random amplification with short primers
- D Detection restricted only to coding regions
Correct answer: Random amplification with short primers
RAPD uses short arbitrary primers to amplify random DNA segments. It does not require prior sequence information.
Which molecular marker technique combines restriction digestion and PCR?
- A RFLP
- B AFLP
- C STR analysis
- D SNP genotyping
Correct answer: AFLP
AFLP involves restriction digestion followed by selective PCR amplification. It generates numerous polymorphic markers.
DNA fingerprinting patterns are usually visualized as:
- A Fluorescent dots
- B Chromosome spreads
- C Banding patterns
- D 3D structures
Correct answer: Banding patterns
DNA fragments form distinct bands after electrophoresis and detection. The pattern of bands constitutes the DNA fingerprint.
Which molecular marker is most useful for population genetics studies?
- A Short tandem repeats (STRs)
- B SNPs
- C VNTRs
- D All of these markers
Correct answer: All of these markers
STRs, SNPs, and VNTRs all reveal genetic variation. Each has applications in population genetics depending on study scale.
The main advantage of SNP markers is their:
- A Extremely high mutation rate at each site
- B Very low abundance throughout the genome
- C Stability and widespread distribution
- D Requirement of unusually large DNA samples
Correct answer: Stability and widespread distribution
SNPs are stable and occur frequently across the genome. This makes them valuable for high-resolution genetic mapping.
DNA fingerprinting cannot reliably distinguish between:
- A Unrelated individuals
- B Parent and child
- C Identical twins
- D Siblings
Correct answer: Identical twins
Identical twins have the same DNA sequence. Therefore, DNA fingerprinting cannot differentiate between them.
Which specific type of repetitive DNA sequence was utilized by Sir Alec Jeffreys in the original DNA fingerprinting technique?
- A Variable Number Tandem Repeats (VNTRs)
- B Single Nucleotide Polymorphisms (SNPs)
- C Long Interspersed Nuclear Elements (LINEs)
- D Exonic regions
Correct answer: Variable Number Tandem Repeats (VNTRs)
VNTRs are minisatellites that vary in length between individuals. Jeffreys used a multilocus probe to bind to these conserved core sequences to create the first DNA fingerprints.
In DNA profiling, 'Short Tandem Repeats' (STRs) are considered superior to VNTRs primarily because:
- A They can be PCR amplified from small or degraded DNA
- B They produce much longer, more visible DNA bands
- C They are found only on the Y-chromosome in human males
- D They completely remove any need for gel electrophoresis
Correct answer: They can be PCR amplified from small or degraded DNA
STRs (microsatellites) are short (2-6 bp), making them ideal for PCR amplification. This allows forensic scientists to get results from very small or partially degraded biological samples.
Which of the following molecular markers is classified as 'Dominant,' meaning it cannot distinguish between homozygotes and heterozygotes?
- A RFLP
- B SSR (Microsatellites)
- C SNP
- D RAPD
Correct answer: RAPD
Random Amplified Polymorphic DNA (RAPD) uses arbitrary primers. A band is either present or absent, so it cannot tell if an individual carries one or two copies of the allele.
What is the role of the 'Capillary Electrophoresis' in modern CODIS (Combined DNA Index System) profiling?
- A To separate fluorescently labeled STR fragments by size
- B To extract and purify genomic DNA from buccal cheek swabs
- C To hybridize denatured DNA fragments with radioactive probes
- D To count the number of mitochondria in a single cell
Correct answer: To separate fluorescently labeled STR fragments by size
Modern profiling uses automated capillary electrophoresis. It separates PCR-amplified STRs by size, and a laser detects fluorescent tags to produce an electropherogram.
Which molecular marker technique involves the use of 'Adaptors' being ligated to restriction fragments before PCR amplification?
- A AFLP
- B RFLP
- C STR
- D VNTR
Correct answer: AFLP
Amplified Fragment Length Polymorphism (AFLP) involves digesting DNA, ligating specific adaptors to the ends, and then using selective primers to amplify specific sets of fragments.
In a paternity test, a child's DNA fingerprint must show:
- A Bands that are completely unique and absent from both parents
- B Only bands that closely match the mother's genetic profile
- C Bands matching the father's profile with complete exact certainty
- D Every band matching either the mother's or the father's profile
Correct answer: Every band matching either the mother's or the father's profile
Since a child inherits half their nuclear DNA from each parent, every band in the child's profile must have a corresponding match in either the maternal or paternal profile.
The 'CODIS' system used by the FBI typically analyzes how many core STR loci for human identification?
- A 2 loci
- B 5 loci
- C 100 loci
- D 20 loci
Correct answer: 20 loci
As of 2017, the CODIS core loci were expanded to 20 to increase the power of discrimination and reduce the likelihood of accidental matches between unrelated individuals.
Which molecular marker is specifically used to track paternal lineage in humans?
- A mtDNA (Mitochondrial DNA)
- B Autosomal STR markers
- C SNPs on Chromosome 21
- D Y-chromosome STR markers
Correct answer: Y-chromosome STR markers
The Y-chromosome is passed virtually unchanged from father to son. Y-STRs are useful in forensic cases involving multiple male contributors or for tracing male ancestry.
Which phenomenon causes the 'Stutter' peaks often seen during the PCR amplification of STR markers?
- A Slipped-strand mispairing by DNA polymerase enzyme
- B Cross-contamination from another individual's sample
- C Inefficient digestion by restriction enzymes
- D Incomplete denaturation of the double-stranded DNA
Correct answer: Slipped-strand mispairing by DNA polymerase enzyme
Stutter occurs when the DNA polymerase slips during replication of repetitive sequences, usually resulting in a minor peak one repeat unit shorter than the main allele.
A 'Single Nucleotide Polymorphism' (SNP) is defined as a variation occurring at a specific position in the genome in at least what percentage of the population?
- A 5%
- B 1%
- C 10%
- D 50%
Correct answer: 1%
By convention, for a single base change to be classified as a polymorphism (SNP) rather than a rare mutation, it must occur in at least 1% of the population.
Mitochondrial DNA (mtDNA) profiling is particularly useful in forensics for identifying remains when:
- A The sample is a fresh, well-preserved blood stain
- B Only hair shafts, old bones, or teeth are available
- C A male suspect's paternal lineage needs identification
- D The nuclear DNA is completely intact and undegraded
Correct answer: Only hair shafts, old bones, or teeth are available
mtDNA is present in high copy numbers per cell and is very robust. It can often be recovered from samples where nuclear DNA has degraded, like ancient bones or hair without a root.
Which molecular marker relies on the 'loss' or 'gain' of a restriction site due to a mutation?
- A RFLP
- B RAPD
- C SSR
- D VNTR
Correct answer: RFLP
RFLP (Restriction Fragment Length Polymorphism) detects variations in the length of DNA fragments produced by restriction enzymes because mutations alter the recognition sequences.
What does the term 'Polymorphic Information Content' (PIC) refer to in molecular biology?
- A The speed at which a gel electrophoresis run is completed
- B The ability of a marker to distinguish between genotypes in a population
- C The amount of template DNA required for a typical PCR amplification setup
- D The number of genes located on a specific chromosome region
Correct answer: The ability of a marker to distinguish between genotypes in a population
PIC is a measure used to evaluate the informativeness of a genetic marker. A high PIC value indicates that the marker is highly variable and useful for linkage mapping or identification.
Which of the following is a drawback of using RAPD markers?
- A They require high concentrations of DNA
- B They are very expensive to develop
- C Low reproducibility between different laboratories
- D They require prior knowledge of the genome sequence
Correct answer: Low reproducibility between different laboratories
RAPDs use low stringency PCR and short primers, making them sensitive to minor changes in reaction conditions. This often results in low reproducibility across different labs.
In the context of DNA fingerprinting, what is 'Amelogenin' used for?
- A Determining the approximate age of the sample
- B Determining the biological sex of the individual
- C Determining the ethnic background of the donor
- D Amplifying mitochondrial DNA sequences for analysis
Correct answer: Determining the biological sex of the individual
The Amelogenin gene is found on both X and Y chromosomes but differs in length. Amplifying this region allows forensic scientists to determine if a sample came from a male or female.
Which molecular marker is considered 'Co-dominant'?
- A RAPD
- B AFLP
- C SSR
- D ISSR
Correct answer: SSR
Simple Sequence Repeats (SSRs) are co-dominant markers. They allow researchers to clearly distinguish between individuals that are homozygous or heterozygous for a specific allele.
What is the primary purpose of 'Allelic Ladders' in STR analysis?
- A To act as a reference DNA template for the unknown crime scene sample
- B To provide a reference for known allele sizes to ensure accurate genotype calling
- C To clean and recondition the capillary electrophoresis column after each run
- D To prevent the extracted DNA sample from denaturing during long-term storage
Correct answer: To provide a reference for known allele sizes to ensure accurate genotype calling
An allelic ladder contains all common known alleles for a specific locus. By comparing the sample peaks to the ladder, the software can precisely identify the number of repeats.
The 'Probability of Identity' (Pi) in forensics measures:
- A The chance that two unrelated individuals will have the same DNA profile
- B The overall likelihood that the identified suspect is guilty of the crime
- C The total number of cells recovered in a crime scene sample
- D The speed at which DNA degrades under crime scene conditions
Correct answer: The chance that two unrelated individuals will have the same DNA profile
Pi is a statistical calculation. The lower the Pi, the more powerful the DNA profile is at uniquely identifying an individual.
Which molecular marker is best suited for high-throughput automated genotyping using DNA microarrays?
- A RFLP
- B VNTR
- C SNP
- D RAPD
Correct answer: SNP
SNPs are single-base variations. Their simple nature makes them ideal for large-scale automation and detection using DNA chips or microarrays.
In 'Southern Blotting,' the DNA is transferred from the gel to a membrane primarily to:
- A Make the denatured DNA double-stranded once more
- B Allow for hybridization with a specific labeled probe
- C Increase the overall molecular weight of the DNA
- D Remove residual Ethidium Bromide staining from the gel
Correct answer: Allow for hybridization with a specific labeled probe
DNA in a gel is fragile and difficult to work with. Transferring it to a sturdy nylon or nitrocellulose membrane allows probes to bind to specific sequences for visualization.