Define a cistron. Giving examples,differentiate between monocistronic and polycistronic transcription units.
(N/A) cistron is defined as a segment of $DNA$ that contains the genetic information coding for a single polypeptide chain or a functional trait.
$1.$ Monocistronic transcription unit: These contain a single structural gene that codes for one polypeptide. This is characteristic of eukaryotes. Example: The structural gene for human insulin or hemoglobin.
$2.$ Polycistronic transcription unit: These contain multiple structural genes under the control of a single promoter and terminator,coding for several polypeptides. This is characteristic of prokaryotes (bacteria). Example: The $lac$ operon in $E. coli$.
In eukaryotes,monocistronic genes are often 'split' or 'interrupted' by non-coding sequences called introns. The coding sequences that appear in the mature $RNA$ are called exons.
$1.$ Monocistronic transcription unit: These contain a single structural gene that codes for one polypeptide. This is characteristic of eukaryotes. Example: The structural gene for human insulin or hemoglobin.
$2.$ Polycistronic transcription unit: These contain multiple structural genes under the control of a single promoter and terminator,coding for several polypeptides. This is characteristic of prokaryotes (bacteria). Example: The $lac$ operon in $E. coli$.
In eukaryotes,monocistronic genes are often 'split' or 'interrupted' by non-coding sequences called introns. The coding sequences that appear in the mature $RNA$ are called exons.
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Similar Questions
Which of the following are the post-transcriptional events in an eukaryotic cell?
$A.$ Transport of pre-mRNA to cytoplasm prior to splicing.
$B.$ Removal of introns and joining of exons.
$C.$ Addition of methyl group at $5$' end of hnRNA.
$D.$ Addition of adenine residues at $3$' end of hnRNA.
$E.$ Base pairing of two complementary RNAs.
Choose the correct answer from the options given below:
$A.$ Transport of pre-mRNA to cytoplasm prior to splicing.
$B.$ Removal of introns and joining of exons.
$C.$ Addition of methyl group at $5$' end of hnRNA.
$D.$ Addition of adenine residues at $3$' end of hnRNA.
$E.$ Base pairing of two complementary RNAs.
Choose the correct answer from the options given below:
DifficultNEET 2025
View SolutionDescribe the process of transcription in prokaryotes (bacteria).
What will be the sequence of $mRNA$ produced by the following stretch of $DNA$?
$3' ATGCATGCATGCATG 5'$ $TEMPLATE$ $STRAND$
$5' TACGTACGTACGTAC 3'$ $CODING$ $STRAND$
$3' ATGCATGCATGCATG 5'$ $TEMPLATE$ $STRAND$
$5' TACGTACGTACGTAC 3'$ $CODING$ $STRAND$
MediumNEET 2019
View SolutionDo you think that the alternate splicing of exons may enable a structural gene to code for several isoproteins from one and the same gene? If yes,how? If not,why so?
Medium
View SolutionGiven below are two statements, one is labelled Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A) :$ In eukaryotes, primary transcripts $(hnRNA)$ contain both exons and introns, and introns are non-functional.
Reason $(R) :$ In bacteria, the $mRNA$ does not require any processing, and transcription and translation take place in the same compartment.
In the light of the above statements, choose the most appropriate answer from the options given below $:$
Assertion $(A) :$ In eukaryotes, primary transcripts $(hnRNA)$ contain both exons and introns, and introns are non-functional.
Reason $(R) :$ In bacteria, the $mRNA$ does not require any processing, and transcription and translation take place in the same compartment.
In the light of the above statements, choose the most appropriate answer from the options given below $:$
Medium
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