DNA Fingerprinting Questions in English

(D) $DNA$ fingerprinting ($=$ $DNA$ typing $=$ $DNA$ profiling $=$ genetic fingerprinting) was invented by Sir Alec Jeffreys of the $UK$ in $1985$.
It is a technique used to identify an individual based on their unique $DNA$ specificity.
During this process,the dark bands observed on an $X$-ray film represent the $DNA$ fingerprint (also known as $DNA$ profiles).
This technique is highly effective in identifying criminals in cases of rape or murder (using biological samples like blood,semen,or hair) and is also used to resolve disputes related to parentage and paternity.

(B) Variable Number Tandem Repeats $(VNTRs)$ are short nucleotide sequences that are repeated in tandem.
The number of these repeats varies from person to person,making them highly polymorphic.
Because these sequences are inherited,they serve as unique genetic markers for individuals.
These are identified through molecular analysis of $DNA$ samples and are the fundamental basis for $DNA$ fingerprinting.

(A) probe is typically a single-stranded $DNA$ or $RNA$ molecule tagged with a radioactive isotope.
In the given question,the probe is described as $dsDNA$ (double-stranded $DNA$).
Double-stranded $DNA$ cannot hybridise directly to its complementary sequence because the strands are already base-paired with each other.
Therefore,the statement that the probe is $dsDNA$ is incorrect,as probes must be single-stranded to allow for hybridisation with the target sequence.

(B) $DNA$ fingerprinting is a technique used to identify individuals by analyzing specific regions of $DNA$ known as repetitive $DNA$.
These regions consist of short sequences of nucleotides that are repeated many times,often referred to as Variable Number Tandem Repeats $(VNTRs)$.
These sequences show a high degree of polymorphism,meaning they vary significantly between individuals,which allows for unique identification.
While satellite $DNA$ is the category to which these repetitive sequences belong,the specific regions analyzed for fingerprinting are the repetitive $DNA$ sequences.

(C) The technique used to detect mutated genes is based on the principle of molecular hybridization.
$1$. $A$ radioactive probe is a single-stranded $DNA$ or $RNA$ molecule tagged with a radioactive isotope.
$2$. This probe is designed to be complementary to the normal gene sequence.
$3$. When this probe is introduced to a clone of cells,it will hybridize (bind) to the normal gene sequence present in the cells.
$4$. However,if a gene is mutated,the sequence of the mutated gene will differ from the normal gene.
$5$. Due to this difference,the radioactive probe will not be able to form a stable hybrid with the mutated gene.
$6$. Consequently,when the cells are exposed to a photographic film (autoradiography),the normal genes will show up as radioactive signals,while the mutated gene will not appear on the film because the probe failed to bind to it.

(B) $DNA$ polymorphism refers to the variation at the genetic level where multiple alleles exist at a specific locus in a population.
$1$. In $DNA$ fingerprinting,these variations (specifically Variable Number Tandem Repeats or $VNTRs$) are used to identify individuals because the pattern of these repeats is unique to every person.
$2$. In genetic mapping,polymorphism is used to identify the location of genes on chromosomes and to study the inheritance of traits.
Therefore,$DNA$ polymorphism is fundamental to both $DNA$ fingerprinting and genetic mapping.

(D) The $DNA$ sequencing method,specifically the dideoxy chain termination method,was developed by Frederick Sanger in $1977$.
This method is also known as the Sanger sequencing method.
It became the foundation for the $DNA$ sequencing technology used in the Human Genome Project.

(C) $DNA$ fingerprinting is a technique used to identify individuals by their genetic makeup. It was developed by Sir Alec Jeffreys in $1984$ at the University of Leicester. This technique relies on the analysis of variable number tandem repeats $(VNTRs)$,which are unique to every individual except identical twins.

(D) $DNA$ fingerprinting is a technique used to identify individuals based on their unique $DNA$ sequences.
In humans,a child inherits $50\%$ of their genetic material from their mother and $50\%$ from their father.
Consequently,the $DNA$ band pattern observed in a child's $DNA$ fingerprint is a combination of the bands inherited from both parents.
Therefore,the child's $DNA$ fingerprint pattern shows $50\%$ similarity with the mother and $50\%$ similarity with the father.

(B) The process of $DNA$ fingerprinting involves several sequential steps:
$1$. $DNA$ isolation: Extraction of $DNA$ from the sample.
$2$. Restriction digestion: $DNA$ is cut into fragments using restriction endonucleases.
$3$. $PCR$ (Polymerase Chain Reaction): Amplification of specific $DNA$ sequences.
$4$. Electrophoresis: Separation of $DNA$ fragments based on size.
$5$. Blotting: Transferring the separated $DNA$ fragments onto a synthetic membrane (like nylon or nitrocellulose).
$6$. Autoradiography: Hybridization with a radioactive probe and detection using $X$-ray film.
$7$. Analysis: Comparing the banding patterns to identify individuals.
Therefore,the correct sequence is $DNA$ isolation $\rightarrow$ Restriction digestion $\rightarrow$ $PCR$ $\rightarrow$ Electrophoresis $\rightarrow$ Blotting $\rightarrow$ Autoradiography $\rightarrow$ Analysis.

(C) The sensitivity of $DNA$ fingerprinting is significantly increased by using the $Polymerase$ $Chain$ $Reaction$ $(PCR)$.
$PCR$ allows for the amplification of even minute quantities of $DNA$ obtained from a crime scene or biological sample into millions of copies.
This amplification makes it possible to perform $DNA$ profiling even when the initial sample size is very small,thereby enhancing the sensitivity and accuracy of the technique.

(C) molecular probe is a fragment of $DNA$ or $RNA$ of variable length (usually $100-1000$ nucleotides long) which is used in $DNA$ or $RNA$ samples to detect the presence of nucleotide sequences that are complementary to the sequence in the probe.
Key characteristics of a molecular probe include:
$1$. It is a short chain of nucleic acid $(IV)$.
$2$. It is typically single-stranded $(III)$ to allow hybridization with the target sequence.
Therefore,the correct combination is $III$ and $IV$.

(B) $DNA$ fingerprinting was developed by Alec Jeffreys.
$(a)$ It relies on $DNA$ polymorphism,which is the variation at the genetic level,as the basis for identification. This is correct.
$(b)$ It utilizes Variable Number Tandem Repeats (VNTRs) as probes,which are highly polymorphic and useful in identification. This is correct.
$(c)$ Minisatellites are indeed used to synthesize radioactive probes,but they typically range from $0.1$ to $20 \ kb$ in size,and the repeat units are usually $10-60 \ bp$. This statement is generally considered correct in the context of the technology.
$(d)$ Gel electrophoresis is used to separate $DNA$ fragments based on size,not to amplify them. $DNA$ amplification is performed using Polymerase Chain Reaction $(PCR)$. Therefore,statement $(d)$ is incorrect.
Since $(a)$,$(b)$,and $(c)$ are correct and $(d)$ is incorrect,the correct option is $(b)$.

(C) The correct sequence of steps involved in $\text{DNA}$ fingerprinting is as follows:
$1$. Isolation of $\text{DNA}$ $(vi)$
$2$. Digestion of $\text{DNA}$ by restriction endonucleases $(i)$
$3$. Separation of $\text{DNA}$ fragments by electrophoresis $(iii)$
$4$. Blotting (transferring separated fragments to synthetic membranes like nitrocellulose or nylon) $(v)$
$5$. Hybridisation using labelled $\text{VNTR}$ probe $(ii)$
$6$. Detection of hybridised $\text{DNA}$ fragments by autoradiography $(iv)$
Thus,the correct sequence is $(vi, i, iii, v, ii, iv)$.

(C) $VNTRs$ (Variable Number of Tandem Repeats) are short nucleotide repeats in the $DNA$ molecule.
These sequences show a high degree of polymorphism.
The length of the regions having $VNTRs$ varies from person to person,except in the case of monozygotic twins.
Because these sequences are unique to each individual,they serve as the key factor in $DNA$ profiling.
Therefore,Statement $I$ is correct as it describes the nature of $VNTRs$,while Statement $II$ is incorrect because $VNTRs$ are highly variable,not the same,among individuals.

(D) $DNA$ profiling (or $DNA$ fingerprinting) relies on identifying variations in non-coding $DNA$ sequences. These sequences consist of short,tandemly repeating units of base pairs known as Variable Number Tandem Repeats $(VNTRs)$. Because the number of these repeats varies significantly between individuals,they serve as unique genetic markers for identification.

(B) In $DNA$ fingerprinting,the $ds$-$DNA$ (double-stranded $DNA$) fragments separated by gel electrophoresis are treated with an alkaline solution (e.g.,$NaOH$).
This process is known as denaturation,which breaks the hydrogen bonds between the complementary base pairs,converting the $ds$-$DNA$ into $ss$-$DNA$ (single-stranded $DNA$).
This $ss$-$DNA$ is then transferred to a nitrocellulose or nylon membrane for further analysis.

(B) Dr. Lalji Singh,known as the 'Father of $DNA$ Fingerprinting in India',worked on the $Bkm$ (Banded Krait Minor) satellite $DNA$.
He isolated this specific $DNA$ sequence from the $W$ chromosome of the female banded krait ($Bungarus$ $fasciatus$).
This $Bkm$ $DNA$ sequence was found to be highly conserved and was used as a radioactive probe for $DNA$ fingerprinting in humans and other organisms.
Therefore,the correct option is $B$.

(B) $DNA$ fingerprinting is a technique used to identify individuals by their genetic makeup rather than their physical fingerprints.
It involves analyzing specific regions of $DNA$ known as variable number tandem repeats $(VNTRs)$.
Option $A$ is correct because $PCR$ (Polymerase Chain Reaction) is often used to amplify small amounts of $DNA$ for analysis.
Option $B$ is incorrect because $DNA$ fingerprinting is based on the analysis of $DNA$ sequences,not the physical fingerprints found on the skin of an individual.
Option $C$ is correct as it is widely used in forensic science to identify suspects or victims.
Option $D$ is correct as it is a standard method for determining biological paternity.

(B) In the $DNA$ fingerprinting technique,the process involves Southern blotting where $DNA$ fragments are separated by gel electrophoresis and transferred to a membrane.
These $DNA$ fragments are then denatured to form single-stranded $DNA$.
During the hybridization step,a radioactive probe (which is a single-stranded $DNA$ sequence) is added.
This probe binds to its complementary sequence on the membrane,forming a double-stranded $DNA$ hybrid.
However,the intermediate state or the specific molecules involved in the hybridization process that are detected are the single-stranded $DNA$ probes binding to the target $DNA$.
Specifically,the question refers to the nature of the radioactive probe used for hybridization,which is a single-stranded $DNA$ molecule.

(A) In $DNA$ fingerprinting,the genomic $DNA$ is first isolated and then digested with restriction endonucleases.
These enzymes act as molecular scissors that cut the $DNA$ at specific recognition sequences,resulting in the fragmentation of $DNA$ into smaller pieces of varying lengths.
This process is essential for creating the $DNA$ fragments that are subsequently separated by gel electrophoresis.

(D) Alec Jeffreys developed the technique of $DNA$ fingerprinting.
He used $VNTR$ (Variable Number Tandem Repeats) as the genetic marker.
$VNTR$s are short nucleotide repeats that vary in number from person to person,making them highly polymorphic and ideal for $DNA$ profiling.

(C) In the technique of $DNA$ fingerprinting,Variable Number Tandem Repeats $(VNTRs)$ are used as probes. These probes are $Single$ $stranded$ $radioactive$ $DNA$ molecules. During the process,the separated $DNA$ fragments are transferred to a synthetic membrane (like nylon or nitrocellulose) via Southern blotting. These fragments are then hybridized with the radioactive $VNTR$ probe,which binds to the complementary sequences on the membrane. The hybridized fragments are then detected by autoradiography.

(C) The process of $\text{DNA}$ fingerprinting using $\text{VNTR}$ involves the following steps:
$1$. First,the $\text{DNA}$ is isolated and digested by restriction endonucleases $(Y)$.
$2$. The separated $\text{DNA}$ fragments are then transferred (blotted) onto a synthetic membrane like nitrocellulose or nylon $(Z)$.
$3$. Finally,hybridisation is performed using a labelled $\text{VNTR}$ probe $(X)$.
Therefore,the correct sequence is $Y \rightarrow Z \rightarrow X$.

(A) $DNA$ fingerprinting relies on the identification of differences in specific regions of $DNA$ sequences called repetitive $DNA$.
Specifically, it utilizes satellite $DNA$, which consists of short sequences of $DNA$ repeated many times.
These sequences, known as Variable Number Tandem Repeats $(VNTRs)$, show a high degree of polymorphism.
Since the number of repeats varies from person to person, it creates a unique genetic profile for every individual, which forms the fundamental basis of $DNA$ fingerprinting.

(B) Erythrocytes.
Erythrocytes (red blood cells) are not helpful for $DNA$ fingerprinting because mature mammalian erythrocytes lack a nucleus and,consequently,do not contain genomic $DNA$.

(D) The correct option is $D$.
In the $DNA$ fingerprinting technique,the process involves several steps: isolation of $DNA$,digestion of $DNA$ by restriction endonucleases $(REN)$,separation of $DNA$ fragments by electrophoresis,transfer (blotting) of separated $DNA$ fragments to synthetic membranes,and finally,hybridisation using labelled $VNTR$ probes.
Therefore,labelled $VNTR$ probes are specifically used during the hybridisation step to detect the complementary sequences.

(B) The correct answer is $B$.
$DNA$ polymorphism refers to the occurrence of an inheritable mutation in a population at a frequency greater than $0.01$ $(1\%)$.
These variations are the basis of genetic mapping and $DNA$ fingerprinting.

(B) The correct sequence is $C-A-E-B-D$.
The steps involved in $DNA$ fingerprinting are as follows:
$1$. Isolation of $DNA$ from the sample cell.
$2$. Amplification of $DNA$ (if required) using $PCR$.
$3$. Digestion of $DNA$ by restriction endonucleases $(RENS)$ $(C)$.
$4$. Separation of $DNA$ fragments by gel electrophoresis $(A)$.
$5$. Transferring (blotting) of separated $DNA$ fragments to synthetic membranes like nitrocellulose or nylon $(E)$.
$6$. Hybridisation using labelled variable number tandem repeat $(VNTR)$ probe $(B)$.
$7$. Detection of hybridised $DNA$ fragments by autoradiography $(D)$.

(A) In genetic fingerprinting,a 'probe' is a radioactively labelled single-stranded $DNA$ molecule that is complementary to the specific variable number tandem repeat $(VNTR)$ sequences being analyzed.
These probes hybridize with the target $DNA$ fragments on a membrane,allowing for the visualization of specific $DNA$ patterns through autoradiography.
Therefore,the correct option is $(A)$.

(A) The correct answer is $A$.
$DNA$ profiling or $DNA$ fingerprinting requires nucleated cells to extract genomic $DNA$.
$Leucocytes$ (white blood cells) are nucleated cells found in blood,making them the ideal source for $DNA$ extraction.
$Platelets$ are cell fragments lacking a nucleus.
$Erythrocytes$ (mature red blood cells) in humans lack a nucleus and organelles.
$Serum$ is the liquid component of blood remaining after clotting,which does not contain cells or $DNA$.

(D) $PCR$ stands for Polymerase Chain Reaction.
It is a molecular biology technique used to amplify a single copy or a few copies of a segment of $DNA$ across several orders of magnitude,generating thousands to millions of copies of a particular $DNA$ sequence.
In cases where the collected $DNA$ sample is insufficient for analysis like $DNA$ fingerprinting,$PCR$ is used to amplify the available $DNA$ to a sufficient quantity.

(D) The correct sequence for $DNA$ fingerprinting is as follows:
$1$. Isolation of $DNA$ and its digestion by restriction endonucleases $(A)$.
$2$. Separation of $DNA$ fragments by gel electrophoresis $(E)$.
$3$. Transferring (blotting) of separated $DNA$ fragments to synthetic membranes such as nitrocellulose or nylon $(C)$.
$4$. Hybridisation using a labelled $VNTR$ probe $(B)$.
$5$. Detection of hybridised $DNA$ fragments by autoradiography $(D)$.
Therefore,the correct sequence is $A \to E \to C \to B \to D$. Thus,option $(4)$ is correct.