Mix Example-Molecular Basis of Inheritance Questions in English

(A) $1$. Frederick Griffith performed experiments on $Streptococcus$ $pneumoniae$ and discovered the phenomenon of bacterial transformation.
$2$. Francois Jacob and Jacques Monod proposed the $Lac$ operon model to explain gene regulation in prokaryotes.
$3$. Har Gobind Khorana developed chemical methods to synthesize $RNA$ molecules with defined combinations of bases, which helped in deciphering the genetic code.
$4$. Meselson and Stahl provided experimental evidence for the semi-conservative mode of $DNA$ replication using $E. coli$ and $^{15}N$ isotopes.
Therefore, the correct matching is $A-III, B-IV, C-I, D-II$.

(D) Statement $I$ is incorrect because during the process of translation,both $\text{tRNA}$ and $\text{rRNA}$ (as part of the ribosome) interact directly with $\text{mRNA}$. The $\text{tRNA}$ brings amino acids to the $\text{mRNA}$ template,and the ribosome binds to the $\text{mRNA}$ to catalyze protein synthesis.
Statement $II$ is correct because $\text{RNA}$ interference $\text{(RNAi)}$ is a highly conserved biological process in eukaryotes that serves as a mechanism for gene silencing and cellular defense against viral infections and transposons.
Therefore,Statement $I$ is incorrect and Statement $II$ is correct.

(C) The correct matches are as follows:
$A$. Alfred Hershey and Martha Chase performed experiments on bacteriophages to prove that $DNA$ is the genetic material $(IV)$.
$B$. Euchromatin is the region of chromatin that is loosely packed and stains light $(III)$.
$C$. Frederick Griffith conducted the transformation experiment using $Streptococcus pneumoniae$ $(I)$.
$D$. Heterochromatin is the region of chromatin that is densely packed and stains dark $(II)$.
Therefore, the correct sequence is $A-IV, B-III, C-I, D-II$.

(C) Let us analyze each statement:
$(i)$ Incorrect: Eukaryotic $\text{mRNA}$ is monocistronic,while prokaryotic $\text{mRNA}$ is polycistronic.
$(ii)$ Correct: Prokaryotic $\text{mRNA}$ lacks a $5'$-cap and a $3'$-poly-$A$ tail,whereas eukaryotic $\text{mRNA}$ undergoes post-transcriptional modifications including capping and tailing.
$(iii)$ Incorrect: The precursor of eukaryotic $\text{mRNA}$ is $\text{hnRNA}$ (heterogeneous nuclear $RNA$),not prokaryotic.
$(iv)$ Incorrect: In replication,both strands of $DNA$ act as templates for the synthesis of new strands.
$(v)$ Correct: In eukaryotes,transcription occurs inside the nucleus,and the resulting $\text{mRNA}$ is transported to the cytoplasm for translation.
Therefore,statements $(ii)$ and $(v)$ are correct.

(C) The correct matches are as follows:
$a.$ Termination: In protein synthesis,termination is mediated by a $GTP$ dependent release factor that recognizes the stop codon $(iii)$.
$b.$ Translation: The process of charging $t-RNA$ with specific amino acids is catalyzed by the enzyme Aminoacyl $t-RNA$ synthetase $(i)$.
$c.$ Transcription: This process involves the synthesis of $RNA$ from a $DNA$ template,catalyzed by the enzyme $RNA$ polymerase $(iv)$.
$d.$ $DNA$ replication: During $DNA$ replication,the lagging strand is synthesized in short segments known as Okazaki fragments $(ii)$.
Therefore,the correct combination is $a-iii, b-i, c-iv, d-ii$.

(B) The split gene arrangement (presence of introns and exons) is considered an ancient feature of the genome because it is found in most eukaryotes,suggesting it was present early in evolutionary history.
Assertion $(A)$ is correct.
$
\text{hnRNA}$ (heterogeneous nuclear $RNA$) undergoes processing steps including splicing (removal of introns),capping (addition of methyl guanosine triphosphate at the $5'$ end),and tailing (addition of poly-$A$ tail at the $3'$ end) to become functional mRNA.
Reason $(R)$ is also a correct statement regarding $\text{hnRNA}$ processing.
However,the reason provided does not explain why the split gene arrangement is considered an ancient feature.
Therefore,both statements are correct,but $(R)$ is not the correct explanation of $(A)$.

(C) $1$. $\text{DNA}$ replication occurs during the $S-$phase (Synthesis phase) of the eukaryotic cell cycle.
$2$. The semi-conservative mode of $\text{DNA}$ replication was proposed by Watson and Crick,but it was experimentally proven by Meselson and Stahl.
$3$. $\text{DNA}$ was first identified by Friedrich Miescher in $1869$,who named it 'nuclein'. It was not identified by Franklin.
$4$. $\text{DNA}$ is indeed a long polymer of deoxyribonucleotides.
$5$. Therefore,statement $C$ is incorrect because Friedrich Miescher,not Franklin,identified $\text{DNA}$ as an acidic substance in the nucleus.

(C) The correct answer is $C$. $\text{mRNA}$ (messenger $\text{RNA}$) is a single-stranded molecule that carries the genetic code from $\text{DNA}$ to the ribosome for protein synthesis. It is composed of nucleotides,not proteins. Proteins are synthesized based on the information carried by $\text{mRNA}$.
- Some $\text{rRNA}$ (ribosomal $\text{RNA}$) act as ribozymes (catalysts),such as $23S \ \text{rRNA}$ in bacteria.
- $\text{tRNA}$ (transfer $\text{RNA}$) possesses an amino acid acceptor end (the $3'$ end) to which a specific amino acid binds.
- In eukaryotic cells,$\text{snRNA}$ (small nuclear $\text{RNA}$) is indeed transcribed by $\text{RNA}$ polymerase $\text{III}$.

(C) The correct answer is $C$.
In the process of translation,termination is mediated by release factors (proteins) that recognize stop codons $(UAA, UAG, UGA)$.
There is no specific $tRNA$ that acts as a 'terminator $tRNA$' to stop the translation process.
Option $A$ is correct as nucleosomes are the repeating units of chromatin.
Option $B$ is correct because $DNA$ lacks the $2'-OH$ group present in $RNA$,making it more stable.
Option $D$ is correct because $PCR$ (Polymerase Chain Reaction) allows for the amplification of $DNA$ from a single cell,making it sufficient for $DNA$ fingerprinting.

(C) Statement $(a)$ is correct: In bacteria,since there is no defined nucleus,transcription and translation take place in the same compartment and can be coupled.
Statement $(b)$ is incorrect: Split gene arrangements (presence of introns) are considered a primitive feature,not an advanced one.
Statement $(c)$ is correct: Splicing involves the removal of introns and joining of exons,which is a process mediated by ribozymes ($RNA$ catalysts),reflecting the $RNA$-world hypothesis.
Statement $(d)$ is correct: The presence of introns in split genes is considered a remnant of the ancient $RNA$ world,indicating the antiquity of this genomic structure.
Therefore,statements $(a), (c),$ and $(d)$ are correct.

(B) The correct matches are as follows:
$1$. $(a)$ Lactose acts as an inducer for the $Lac$ operon,which binds to the repressor protein to allow transcription. Thus,$(a)-(ii)$.
$2$. $(b)$ Release factor is a protein that recognizes the stop codon on mRNA and facilitates the termination of translation. Thus,$(b)-(iv)$.
$3$. $(c)$ Histones are basic proteins around which negatively charged $\text{DNA}$ is wrapped for packaging into chromatin. Thus,$(c)-(iii)$.
$4$. $(d)$ Exons are the coding sequences in a gene that are expressed as part of the final mRNA. Thus,$(d)-(i)$.
Therefore,the correct sequence is $(a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)$.

(C) Statement $(A)$ is correct: $\text{RNA}$ is considered the first genetic material and plays a central role in essential life processes like metabolism,translation,and splicing.
Statement $(B)$ is incorrect: $^{15}N$ is a stable heavy isotope,not a radioactive one.
Statement $(C)$ is incorrect: Codons are present in $\text{mRNA}$,not $\text{rRNA}$.
Statement $(D)$ is correct: The first step of translation is the activation of amino acids,which requires $\text{ATP}$ and specific aminoacyl-tRNA synthetases.
Statement $(E)$ is incorrect: $\text{DNA}$ from every tissue of an individual is identical; polymorphism is observed between different individuals,not between tissues of the same individual.
Therefore,only statements $(A)$ and $(D)$ are correct.

(A) The correct matching is as follows:
$A$. Monocistronic gene: These are genes that code for a single polypeptide chain and are found mostly in eukaryotes $(IV)$.
$B$. Polycistronic gene: These are genes that code for multiple polypeptide chains and are found mostly in prokaryotes $(III)$.
$C$. Exons: These are the coding sequences that appear in mature $RNA$ $(I)$.
$D$. Introns: These are the intervening sequences that do not code for proteins and are removed during $RNA$ splicing $(II)$.
Therefore,the correct sequence is $(A-IV), (B-III), (C-I), (D-II)$.

(A) Statement-$I$ is correct: The presence of split genes (introns and exons) is considered an ancient feature of the genome,often referred to as the 'exon theory of genes'.
Statement-$II$ is correct: During the process of post-transcriptional modification (splicing),the non-coding sequences known as introns are removed,and the coding sequences (exons) are joined together to form mature or processed $\text{mRNA}$. Therefore,introns do not appear in the final mature $\text{RNA}$.

(A) The correct matching is as follows:
$1$. Ligase: This enzyme is responsible for joining $DNA$ fragments,specifically the Okazaki fragments during $DNA$ replication $(1-c)$.
$2$. Ribozyme: This is an $RNA$ molecule that acts as an enzyme,specifically catalyzing the formation of peptide bonds during protein synthesis $(2-a)$.
$3$. Permease: This is a membrane transport protein that increases the permeability of the cell membrane to specific substances like lactose $(3-d)$.
$4$. $\beta$-galactosidase: This enzyme catalyzes the hydrolysis of lactose into glucose and galactose $(4-b)$.
Therefore,the correct sequence is $1-c, 2-a, 3-d, 4-b$.

(C) The correct matches are as follows:
$i$. Avery,McCarty,and MacLeod $(a)$: They demonstrated that $DNA$ is the transforming principle by showing that DNAse treatment inhibits the transformation of $R$ cells to $S$ cells.
$ii$. Griffith $(c)$: Frederick Griffith performed the transformation experiment using $Streptococcus$ $pneumoniae$ (bacterium causing pneumonia).
$iii$. Hershey and Chase $(d)$: They used radioactive isotopes of Sulphur $(^{35}S)$ and Phosphorus $(^{32}P)$ to prove that $DNA$ is the genetic material in bacteriophages.
$iv$. Meselson and Stahl $(b)$: They experimentally proved that $DNA$ replication is semi-conservative using $E. coli$ and $^{15}N$ isotopes.
Therefore,the correct matching is $i-a, ii-c, iii-d, iv-b$.

(C) Statement $I$ is correct: $DNA$ performs two types of functions: autocatalytic (replication) and heterocatalytic (transcription and translation). In heterocatalytic function,$DNA$ directs the synthesis of other molecules like $RNA$ and proteins.
Statement $II$ is correct: The complementary base pairing between the two strands of $DNA$ (where $A$ pairs with $T$ and $G$ pairs with $C$) is the fundamental property that allows each strand to serve as a template for the synthesis of a new complementary strand,thus facilitating semiconservative replication.
Therefore,both statements are correct.

(D) The segment of $DNA$ that codes for a polypeptide or a functional $RNA$ molecule,and is responsible for the inheritance and expression of a particular character,is called a $cistron$.
$1$. $Recon$ is the smallest unit of $DNA$ capable of recombination.
$2$. $Muton$ is the smallest unit of $DNA$ capable of undergoing mutation.
$3$. $Intron$ is a non-coding sequence of $DNA$ that is removed during $RNA$ splicing.
$4$. $Cistron$ is the functional unit of inheritance,corresponding to a gene.

(B) Option $B$ is correct. $rRNA$ (ribosomal $RNA$) acts as a structural and catalytic component of ribosomes and is characterized by complex secondary structures due to extensive folding.
- Option $A$ is incorrect because $DNA$ strands are anti-parallel and complementary to each other.
- Option $C$ is incorrect because both leading and lagging strands are synthesized in the $5' \rightarrow 3'$ direction by $DNA$ polymerase.
- Option $D$ is incorrect because $mRNA$ is typically a linear molecule that carries the genetic code; it does not typically form hairpin structures like $tRNA$ or $rRNA$.

(B) The 'Central dogma' of molecular biology was proposed by Francis Crick in $1958$.
It describes the flow of genetic information within a biological system.
The process involves the flow of information from $DNA$ to $RNA$ (transcription) and from $RNA$ to protein (translation).
Therefore,$X$ is Francis Crick,$Y$ is transcription,and $Z$ is translation.
The correct option is $B$.

(B) . $VNTR$ (Variable Number Tandem Repeats) are used in $DNA$ fingerprinting $(A-q)$.
$B$. Introns and exons are processed during the splicing of $hnRNA$ $(B-s)$.
$C$. Dystrophin is known as the largest gene in humans $(C-p)$.
$D$. Satellite $DNA$ is separated from the main genomic $DNA$ as a peak during density gradient centrifugation,often referred to as bulk $DNA$ $(D-r)$.
Therefore,the correct matching is $A-q, B-s, C-p, D-r$.

$(C)$. Griffith performed the transformation experiment, which led to the discovery of the "Transforming principle" $(A-iii)$.
$B$. Jacob and Monod proposed the "Lac operon" model to explain gene regulation in bacteria $(B-i)$.
$C$. Meselson and Stahl provided experimental evidence that "$DNA$ replicates semiconservatively" $(C-iv)$.
$D$. Hershey and Chase used bacteriophages to prove that "$DNA$ is the genetic material" $(D-ii)$.
Therefore, the correct match is $A-iii, B-i, C-iv, D-ii$.

(B) The correct matches are as follows:
$1$. $(A)$ $DNA$ replication: This process involves the synthesis of a new $DNA$ strand from a $DNA$ template,catalyzed by the enzyme $(q)$ $DNA$ polymerase.
$2$. $(B)$ Translation: This process involves the synthesis of proteins from mRNA. The enzyme $(s)$ Aminoacyl-tRNA synthetase is responsible for charging the tRNA with the appropriate amino acid.
$3$. $(C)$ Transcription: This process involves the synthesis of $RNA$ from a $DNA$ template,catalyzed by the enzyme $(p)$ $RNA$ polymerase.
$4$. $(D)$ Reverse transcription: This process involves the synthesis of $DNA$ from an $RNA$ template,catalyzed by the enzyme $(r)$ Reverse transcriptase.
Therefore,the correct matching is $A-(q), B-(s), C-(p), D-(r)$.

(D) Statement $(A)$ is correct: In a transcription unit,the promoter is located at the $5'$ end of the coding strand (upstream).
Statement $(B)$ is incorrect: The template strand has a polarity of $3' \rightarrow 5'$,which allows $RNA$ polymerase to synthesize $RNA$ in the $5' \rightarrow 3'$ direction.
Statement $(C)$ is incorrect: $RNA$ polymerase binds to the promoter,not the operator,to initiate transcription.
Statement $(D)$ is correct: Single base $DNA$ differences occurring in humans are known as Single Nucleotide Polymorphisms $(SNPs)$.
Therefore,statements $(A)$ and $(D)$ are correct.